Patent Publication Number: US-2019197400-A1

Title: Topic classification using a jointly trained artificial neural network

Description:
TECHNICAL FIELD 
     This disclosure generally relates to classification using an artificial neural network. 
     BACKGROUND 
     A social-networking system, which may include a social-networking website, may enable its users (such as persons or organizations) to interact with it and with each other through it. The social-networking system may, with input from a user, create and store in the social-networking system a user profile associated with the user. The user profile may include demographic information, communication-channel information, and information on personal interests of the user. The social-networking system may also, with input from a user, create and store a record of relationships of the user with other users of the social-networking system, as well as provide services (e.g., wall posts, photo-sharing, event organization, messaging, games, or advertisements) to facilitate social interaction between or among users. 
     The social-networking system may send over one or more networks content or messages related to its services to a mobile or other computing device of a user. A user may also install software applications on a mobile or other computing device of the user for accessing a user profile of the user and other data within the social-networking system. The social-networking system may generate a personalized set of content objects to display to a user, such as a newsfeed of aggregated stories of other users connected to the user. 
     SUMMARY OF PARTICULAR EMBODIMENTS 
     In particular embodiments, an artificial neural network (“ANN”) may be jointly trained to determine a topic of a post based on text of the post (e.g., one or more n-grams) and an image of the post. The ANN may be trained based on a corpus of training pages each comprising training posts. Each training post may comprise text and an image. The input to the ANN may comprise a text vector representing the text of a post and an image vector representing the image of the post. Each the input to each node of an input layer of the ANN may be a component of the text vector or the image vector. The overall input to the input layer of the ANN may be a concatenation of the components of the text vector and the image vector. The ANN may be trained to output a topic of an input post based on a similarity of the input post to training posts of a training page. A jointly trained ANN may refer to an ANN that receives input based on more than one vector. 
     The embodiments disclosed herein are only examples, and the scope of this disclosure is not limited to them. Particular embodiments may include all, some, or none of the components, elements, features, functions, operations, or steps of the embodiments disclosed above. Embodiments according to the invention are in particular disclosed in the attached claims directed to a method, a storage medium, a system and a computer program product, wherein any feature mentioned in one claim category, e.g. method, can be claimed in another claim category, e.g. system, as well. The dependencies or references back in the attached claims are chosen for formal reasons only. However any subject matter resulting from a deliberate reference back to any previous claims (in particular multiple dependencies) can be claimed as well, so that any combination of claims and the features thereof are disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject-matter which can be claimed comprises not only the combinations of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and/or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example vector space. 
         FIG. 2  illustrates an example page. 
         FIG. 3  illustrates an example artificial neural network. 
         FIG. 4  illustrates an example plurality of artificial neural networks. 
         FIG. 5  illustrates an example method for determining a topic of a post. 
         FIG. 6  illustrates an example network environment associated with a social-networking system. 
         FIG. 7  illustrates an example social graph. 
         FIG. 8  illustrates an example computer system. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     In particular embodiments, an artificial neural network (“ANN”) may be jointly trained to determine a topic of a post based on text of the post (e.g., one or more n-grams) and an image of the post. The ANN may be trained based on a corpus of training pages each comprising training posts. Each training post may comprise text and an image. The input to the ANN may comprise a text vector representing the text of a post and an image vector representing the image of the post. Each the input to each node of an input layer of the ANN may be a component of the text vector or the image vector. The overall input to the input layer of the ANN may be a concatenation of the components of the text vector and the image vector. The ANN may be trained to output a topic of an input post based on a similarity of the input post to training posts of a training page. A jointly trained ANN may refer to an ANN that receives input based on more than one vector. 
       FIG. 1  illustrates an example view of a vector space  100 . Vector space  100  may also be referred to as a feature space or an embedding space. In particular embodiments, an object or an n-gram may be represented in a d-dimensional vector space, where d denotes any suitable number of dimensions. Although the vector space  100  is illustrated as a three-dimensional space, this is for illustrative purposes only, as the vector space  100  may be of any suitable dimension. In particular embodiments, an n-gram may be represented in the vector space  100  as a vector. Each vector may comprise coordinates corresponding to a particular point in the vector space  100  (i.e., the terminal point of the vector). As an example and not by way of limitation, vectors  110 ,  120 , and  130  may be represented as points in the vector space  100 , as illustrated in  FIG. 1 . In particular embodiments, a mapping from data to a vector may be relatively insensitive to small changes in the data (e.g., a small change in the data being mapped to a vector will still result in approximately the same mapped vector). In particular embodiments, social-networking system  660  may map objects of different modalities to the same vector space or use a function jointly trained to map one or more modalities to a feature vector (e.g., between visual, audio, text). Although this disclosure may describe a particular vector space, this disclosure contemplates any suitable vector space. 
     In particular embodiments, an n-gram may be mapped to a respective vector representation. As an example and not by way of limitation, n-grams t 1  and t 2  may be mapped to vectors   and   in the vector space  100 , respectively, by applying a function   defined by a dictionary, such that  = (t 1 ) and  = (t 2 ). As another example and not by way of limitation, a dictionary trained to map text to a vector representation may be utilized, or such a dictionary may be itself generated via training. As another example and not by way of limitation, a model, such as Word2vec, may be used to map an n-gram to a vector representation in the vector space  100 . In particular embodiments, an n-gram may be mapped to a vector representation in the vector space  100  by using a machine leaning model (e.g., a neural network). The machine learning model may have been trained using training data (e.g., a corpus of objects each comprising n-grams). Although this disclosure describes representing an n-gram in a vector space in a particular manner, this disclosure contemplates representing an n-gram in a vector space in any suitable manner. 
     In particular embodiments, an object may be represented in the vector space  100  as a vector. As an example and not by way of limitation, objects e 1  and e 2  may be mapped to vectors   and   in the vector space  100 , respectively, by applying a function  , such that  = (e 1 ) and  = (e 2 ). In particular embodiments, an object may be mapped to a vector based on one or more properties, attributes, or features of the object, relationships of the object with other objects, or any other suitable information associated with the object. As an example and not by way of limitation, a function   may map objects to vectors by feature extraction, which may start from an initial set of measured data and build derived values (e.g., features). As an example and not by way of limitation, an object comprising a video or an image may be mapped to a vector by using an algorithm to detect or isolate various desired portions or shapes of the object. Features used to calculate the vector may be based on information obtained from edge detection, corner detection, blob detection, ridge detection, scale-invariant feature transformation, edge direction, changing intensity, autocorrelation, motion detection, optical flow, thresholding, blob extraction, template matching, Hough transformation (e.g., lines, circles, ellipses, arbitrary shapes), or any other suitable information. As another example and not by way of limitation, an object comprising audio data may be mapped to a vector based on features such as a spectral slope, a tonality coefficient, an audio spectrum centroid, an audio spectrum envelope, a Mel-frequency cepstrum, or any other suitable information. In particular embodiments, when an object has data that is either too large to be efficiently processed or comprises redundant data, a function   may map the object to a vector using a transformed reduced set of features (e.g., feature selection). In particular embodiments, a function   may map an object e to a vector  (e) based on one or more n-grams associated with object e. In particular embodiments, an object may be mapped to a vector by using a machine learning model. Although this disclosure describes representing an object in a vector space in a particular manner, this disclosure contemplates representing an object in a vector space in any suitable manner. 
     In particular embodiments, the social-networking system  660  may calculate a similarity metric of vectors in vector space  100 . A similarity metric may be a cosine similarity, a Minkowski distance, a Mahalanobis distance, a Jaccard similarity coefficient, or any suitable similarity metric. As an example and not by way of limitation, a similarity metric of   and   may be a cosine similarity 
     
       
         
           
             
               
                 
                   
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     As another example and not by way of limitation, a similarity metric of   and   may be a Euclidean distance ∥ − ∥. A similarity metric of two vectors may represent how similar the two objects or n-grams corresponding to the two vectors, respectively, are to one another, as measured by the distance between the two vectors in the vector space  100 . As an example and not by way of limitation, vector  110  and vector  120  may correspond to objects that are more similar to one another than the objects corresponding to vector  110  and vector  130 , based on the distance between the respective vectors. In particular embodiments, social-networking system  660  may determine a cluster of vector space  100 . A cluster may be a set of one or more points corresponding to feature vectors of objects or n-grams in vector space  100 , and the objects or n-grams whose feature vectors are in the cluster may belong to the same class or have a relationship to one another (e.g., a semantic relationship, a visual relationship, a topical relationship, etc.). As an example and not by way of limitation, cluster  140  may correspond to sports-related content and another cluster may correspond to food-related content. Although this disclosure describes calculating a similarity metric between vectors in a particular manner, this disclosure contemplates calculating a similarity metric between vectors in any suitable manner. 
     More information on vector spaces, embeddings, feature vectors, and similarity metrics may be found in U.S. patent application Ser. No. 14/949,436, filed 23 Nov. 2015, U.S. patent application Ser. No. 15/286,315, filed 5 Oct. 2016, and U.S. patent application Ser. No. 15/365,789, filed 30 Nov. 2016, each of which is incorporated by reference. 
       FIG. 2  illustrates an example page  200 . In particular embodiments, a page may comprise one or more posts. As an example and not by way of limitation, page  200  comprises posts  220 ,  230 , and  240 . In particular embodiments, a post may comprise one or more n-grams, one or more videos, or one or more images. As an example and not by way of limitation, post  220  may comprise one or more n-grams (e.g., “Mariners acquire Danny Valencia from the Oakland A&#39;s. What move should the Mariners make next?”). As another example and not by way of limitation, post  230  may comprise one or more n-grams and an image of a baseball. As another example and not by way of limitation, post  240  may comprise a video. Although this disclosure may describe particular posts of particular pages, this disclosure contemplates any suitable post and any suitable page. 
     In particular embodiments, a post may have been submitted by a user to a page and comprise content selected by the user. As an example and not by way of limitation, the content of post  220  may have been submitted by the user “Seattle Mariners Fans” to the Seattle Mariners Fans page. In particular embodiments, a post may comprise comments. Additionally or alternatively, comments on a post may be considered separately from each other and the original post. As an example and not by way of limitation, post  230  may comprise the text content “Giving away baseball signed by Ken Griffey Jr to the biggest fan!” and an image of a baseball submitted by user Alice Liddel. The user “The Dormouse” may submit a comment to that post comprising the text “Griffey is my fav, give to me plz!!!” The post by Alice Liddel and the post by The Dormouse may be considered as two separate posts, considered together as one post, or only the post by Alice Liddel may be considered while the comment by The Dormouse may be considered as non-post content. In particular embodiments, a user may select content of a post by generating the content, linking to the content, selecting pre-generated content, or in any other suitable manner. Although this disclosure may describe particular posts with particular content, this disclosure contemplates any suitable post comprising any suitable content. 
     In particular embodiments, a page may correspond to a label comprising one or more n-grams. As an example and not by way of limitation, page  200  may correspond to the label  210  “Seattle Mariners Fans.” In particular embodiments, the label may be a user-generated label that relates to the content of the page. As an example and not by way of limitation, page  200  may be a user created page on a social-networking system  660 . The user who created page  200  may have selected the label “Seattle Mariners Fans” and page  200  may be a page where fans of the Seattle Mariners baseball team may view, post, or interact with content. In particular embodiments, posts on page  200  may relate to label  210 . As an example and not by way of limitation, users who post on page  200  may tend to submit posts to page  200  that relate to the label  210  (e.g., users who want to post Seattle Mariners-related content may self-select page  200  to post related content). As another example and not by way of limitation, an administrator of a page may remove off-topic posts from the page and retain posts that are related to label  210  (e.g., a post unrelated to the Seattle Mariners may be removed from page  200  by an administrator of page  200 ). Although this disclosure describes particular posts on particular pages with a particular label, this disclosure contemplates any suitable post of any suitable page corresponding to any suitable label. 
       FIG. 3  illustrates an example artificial neural network (“ANN”)  300 . In particular embodiments, an ANN may refer to a computational model comprising one or more nodes. Example ANN  300  may comprise input layer  310 , hidden layers  320 ,  330 ,  340 , and output layer  350 . Each layer of ANN  300  may comprise one or more nodes, such as node  305  or node  315 . In particular embodiments, each node of an ANN may be connected to another node of the ANN. As an example and not by way of limitation, each node of input layer  310  may be connected to one of more nodes of hidden layer  320 . In particular embodiments, one or more nodes may be a bias node (e.g., a node in a layer that is not connected to and does not receive input from any node in a previous layer). In particular embodiments, each node in each layer may be connected to one or more nodes of a previous or subsequent layer. Although  FIG. 3  depicts a particular ANN with a particular number of layers, a particular number of nodes, and particular connections between nodes, this disclosure contemplates any suitable ANN with any suitable number of layers, any suitable number of nodes, and any suitable connections between nodes. As an example and not by way of limitation, although  FIG. 3  depicts a connection between each node of input layer  310  and each node of hidden layer  320 , one or more nodes of input layer  310  may not be connected to one or more nodes of hidden layer  320 . 
     In particular embodiments, an activation function may correspond to each node of an ANN. An activation function of a node may define the output of a node for a given input. In particular embodiments, an input to a node may comprise a set of inputs. As an example and not by way of limitation, an activation function may be an identity function, a binary step function, a logistic function, or any other suitable function. As another example and not by way of limitation, an activation function for a node k may be the sigmoid function 
     
       
         
           
             
               
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     where s k  may be the effective input to node k. In particular embodiments, the input of an activation function corresponding to a node may be weighted. Each node may generate output using a corresponding activation function based on weighted inputs. In particular embodiments, an ANN may be a feedforward ANN (e.g., an ANN with no cycles or loops where communication between nodes flows in one direction beginning with the input layer and proceeding to successive layers). As an example and not by way of limitation, the input to each node of hidden layer  320  may comprise the output of one or more nodes of input layer  310 . As another example and not by way of limitation, the input to each node of output layer  350  may comprise the output of one or more nodes of hidden layer  340 . In particular embodiments, each connection between nodes may be associated with a weight. As an example and not by way of limitation, connection  325  between node  305  and node  315  may have a weighting coefficient of 0.4, which may indicate that 0.4 multiplied by the output of node  305  is used as an input to node  315 . As another example and not by way of limitation, the output y k  of node k may be y k (t+1)=F k (y k (t), s k (t)), where F k  may be the activation function corresponding to node k, s k (t)=Σ j (w jk (t)x j (t)+b k (t)) may be the effective input to node k, x j (t) may be the output of a node j connected to node k, w jk  may be the weighting coefficient between node j and node k, and b k  may be an offset parameter. In particular embodiments, the input to nodes of the input layer may be based on one or more vectors representing portions of a post (e.g., one or more n-grams of a post, one or more images of a post, one or more videos of a post, etc.). Although this disclosure describes particular inputs to and outputs of nodes, this disclosure contemplates any suitable inputs to and outputs of nodes. Moreover, although this disclosure may describe particular connections and weights between nodes, this disclosure contemplates any suitable connections and weights between nodes. 
     In particular embodiments, an artificial neural network may be trained to categorize a post. A post may be categorized by determining a semantic meaning, a topic, a label, or any other suitable categorization. In particular embodiments, the ANN may be trained based on a plurality of training pages, each training page comprising one or more training posts. As an example and not by way of limitation, a particular number of training pages may be selected and used to train the ANN. As another example and not by way of limitation, pages with at least a threshold number of training posts (e.g., at least 30 training posts) may be selected and used to train the ANN. In particular embodiments, the ANN may be jointly trained to receive a text vector representing one or more n-grams of a post and an image vector representing an image of the post and then output a probability that the received post is related to the training posts of a training page. Joint training may refer to training an ANN using input from both a text vector and an image vector. As an example and not by way of limitation, a text vector and an image vector may be accessed for each training post. The text vector may represent one or more n-grams of the training post and the image vector may represent an image of the training post. In particular embodiments, the ANN may be trained be modifying the weights associated with connections between nodes of the ANN by optimizing an objective function. As an example and not by way of limitation, a training method may be used (e.g., the conjugate gradient method, the gradient descent method, the stochastic gradient descent) to backpropagate the sum-of-squares error measured as a distances between the each training post vector of a training page (e.g., using a cost function that minimizes the sum-of-squares error). The input to the nodes of input layer  310  may be based on a text vector representing the n-grams of a training post and an image vector representing the image of a training post. As an example and not by way of limitation, each component of the text vector may be an input to a node of input layer  310  and each component of the image vector may be an input to a node of input layer  310 . In particular embodiments, the inputs to the ANN may comprise a concatenation of components of a text vector and components of the image vector. As an example and not by way of limitation, the inputs to input layer  310  may comprise the components of the text vector, which may be input to the nodes of portion  335 , and components of the image vector, which may be input to the nodes of portion  345 . Although this disclosure describes generating a vector representing a post in a particular manner, this disclosure contemplates generating a vector representing a post in any particular manner. Furthermore, although this disclosure describes training an ANN using particular pages or posts or by a particular training method, this disclosure contemplates training an ANN using any suitable pages, any suitable posts, and any suitable training method. As an example and not by way of limitation, an ANN may be jointly trained to receive a text vector and a video vector representing a video of a post and output a probability that the received post is related to the training posts of a training page. 
     In particular embodiments, social-networking system  660  may access an input vector representing an input post. As an example and not by way of limitation, social-networking system  660  may access an input vector representing an input post by accessing an input post and determine a vector representing the input post based on the content of the input post (e.g., using an ANN). As another example and not by way of limitation, social-networking system  660  may access a pre-determined input vector representing an input post without accessing the input post. In particular embodiments, the input vector representing the input post may correspond to a point in a d-dimensional vector space. Although this disclosure describes accessing an input vector in a particular manner, this disclosure contemplates accessing an input vector is any suitable manner. 
     In particular embodiments, a vector representing an input post may be generated by an ANN based on a text vector representing the one or more n-grams of the input post and an image vector representing the image of the input post. As an example and not by way of limitation, referencing  FIG. 2 , a vector representing post  230  may be generated by ANN  300 . The input to the nodes of input layer  310  may be based on a text vector representing the n-grams of post  230  and an image vector representing the image of post  230 . As an example and not by way of limitation, each component of the text vector may be an input to a node of input layer  310  and each component of the image vector may be an input to a node of input layer  310 . In particular embodiments, the inputs to the ANN may comprise a concatenation of components of a text vector and components of the image vector. As an example and not by way of limitation, the inputs to input layer  310  may comprise the components of the text vector, which may be input to the nodes of portion  335 , and components of the image vector, which may be input to the nodes of portion  345 . In particular embodiments, the input vector may comprise an output of one or more activation functions of one or more layers of the ANN. As an example and not by way of limitation, an each component of the input vector be the output (e.g., the evaluation of the activation function) of a node of hidden layer  340 . Although this disclosure describes generating a vector representing a post in a particular manner, this disclosure contemplates generating a vector representing a post in any particular manner. 
     In particular embodiments, the vector space may comprise a plurality of clusters that are each associated with a topic. In particular embodiments, a cluster may refer to a grouping of vectors in the vector space. The cluster may define membership criteria (e.g., a set of rules to determine whether a particular vector is a member of the cluster). As an example and not by way of limitation, each cluster may be represented as a centroid and a vector may be a member of a particular cluster if the vector is closer to the centroid of the particular cluster than the centroid of any other cluster. In particular embodiments, a cluster may be visualized, represented, or defined by a boundary in the vector space. As an example and not by way of limitation, referencing  FIG. 1 , cluster  140  may be visualized as a sphere, where vectors on the interior are members of the cluster and vectors on the exterior are not members (e.g., vectors  110  and  120  may be members of the cluster and vector  130  may not be a member of the cluster). In particular embodiments, a topic may refer to a category, a subject, a property, a concept, a semantic meaning, or an epistemological potential. As an example and not by way of limitation, a cluster may be associated with the topic “baseball,” the topic “food,” the topic “sports,” the topic “local news,” or any other suitable topic. In particular embodiments, the clusters may be mutually exclusive (e.g., a vector may be a member of at most one cluster). In particular embodiments, the clusters may not be mutually exclusive. As an example and not by way of limitation, a vector may be a member of a cluster associated with the topic “sports” and a member of a cluster associated with the topic “baseball.” Each point in the vector space may be within a cluster, or there may exist at least one point in the vector space that is not within any cluster. Although this disclosure describes particular clusters or topics, this disclosure contemplates any suitable clusters and any suitable topics. 
     In particular embodiments, each cluster may be determined based on a clustering of a plurality of training-page vectors corresponding to a plurality of respective training pages that each comprise one or more training posts. Clustering the plurality of training-page vectors may refer to a cluster analysis of the training-page vectors to determine the clusters. As an example and not by way of limitation, a k-means clustering analysis, a hierarchical clustering analysis, a distribution-based clustering analysis, a density-based clustering analysis, or any other suitable clustering analysis may be used to determine clusters based on the training-page vectors. In particular embodiments, a clustering analysis may determine a particular number of clusters. As an example and not by way of limitation, a clustering analysis may be used to determine 5,000 clusters. In particular embodiments, a clustering analysis may refine cluster assignments through repeated subdivision until a criterion is met. As an example and not by way of limitation, a clustering analysis may continue to subdivide cluster assignments until a subsequent subdivision results in a model with a higher Bayesian information criterion than the previously subdivided model. In particular embodiments, each training post may have been submitted by a user to a training page and comprise content selected by the user. As an example and not by way of limitation, referencing  FIG. 2 , page  200  may be a training page and post  220  may be a training post of training page  200 . Post  220  may have been submitted by the user “Seattle Mariners Fans” to page  200  and post  220  may comprise content selected by the user “Seattle Mariners Fans.” Although this disclosure describes particular clustering using a particular clustering analysis, this disclosure contemplates any suitable clustering using any suitable clustering analysis. 
     In particular embodiments, each training-page vector may be generated by an ANN that was trained, based on the training posts of training pages associated with the ANN, to receive a post and then output, for each training page, a probability that the received post is related to the training posts of the training page. As an example and not by way of limitation, the ANN may be trained such that a layer (e.g., an output layer) of the ANN comprises nodes corresponding to the training pages. For a received post, the ANN may output a binary decision of the received post for each training page as to whether the received post is related to the training posts of the training page. As another example and not by way of limitation, the ANN may output, for each training page, a probability that a received post is related to the training page (e.g., a probability from 0 to 1.0). As another example and not by way of limitation, the ANN may output a rank for each training page indicating which of the training pages comprise training posts most similar to the received post (e.g., the received post is most related to the top ranked training page, least similar to the bottom ranked training page, etc.). As another example and not by way of limitation, the ANN may comprise a projection matrix. The projection matrix may comprise weights assigned to each element of a vector representing a received post for each training page. Each column of the projection matrix may represent a training page. For a training page i, the activation A i =w i ×H, where w i  may be a weight vector corresponding to training page i and H may be the vector representing the received post. The value of A i  may represent the probability that the received post is related to training page i. In particular embodiments, a page vector representing a page may comprise a hidden layer of the ANN that generated the page vector. The projection matrix may be the matrix that transforms the hidden layer to the output layer. In particular embodiments, the probability that the received post is related to the training posts of the training page may comprise a probability that the received post is semantically related to the training posts of the training page. Although this disclosure describes particular probabilities outputted by a particular ANN trained in a particular manner, this disclosure contemplates any suitable probability outputted by any suitable ANN trained in any suitable manner. 
       FIG. 4  illustrates an example plurality of ANNs. In particular embodiments, the plurality of training-page vectors may be generated by a plurality of ANNs. As an example and not by way of limitation, ANN shard  410 , ANN shard  420 , and ANN shard  430  may each correspond to a different ANN. Each ANN may be associated with one or more of the training pages. As an example and not by way of limitation, ANN shard  410  may be associated with training pages  405 , ANN shard  420  may be associated with training pages  415 , and ANN shard  430  may be associated with training pages  425 . In particular embodiments, each ANN may be trained, based on the training posts of the training pages associated with the ANN, to receive a post and output, for each associated training page, a probability that the post is related to the training posts of the training page. As an example and not by way of limitation, ANN shard  410  may be trained based on the training posts of training pages  405  to output a probability that a received post is related to the training posts of each training page of training pages  405 . Each ANN may be trained separately from one another. In particular embodiments, one or more of the training pages may be common pages associated with all of the ANNs. As an example and not by way of limitation, one or more training pages in  FIG. 4  may be common pages  402 . Training pages  405  may comprise common pages  402 , training pages  415  may comprise common pages  402 , and training pages  425  may comprise common pages  402 . Although this disclosure describes a particular plurality of ANNs associated with particular training pages, this disclosure contemplates using any suitable number of any suitable ANNs associated with any suitable training pages. 
     Training-page vectors generated by a plurality of ANNs may be mapped to a common vector space of a particular one of the ANNs. For each training page associated with the particular ANN, the particular ANN may generate a training-page vector representing the training page. For each training page associated with each other ANN corresponding to a respective other vector space, the other ANN may generate an intermediate-page vector representing the training page. For each of the other ANNs, a mapping from the other vector space corresponding to the other ANN to the particular vector space corresponding to the particular ANN may be determined based on the training-page vectors representing the common pages generated by the particular ANN and the intermediate-page vectors representing the common pages generated by the other ANN. As an example and not by way of limitation, ANN shard  410  may be the particular ANN. ANN shard  410  may generate training-page vectors representing the common pages  402 . ANN shard  420  may generate intermediate-page vectors representing the common pages  402 . A mapping to the particular vector space corresponding to ANN shard  410  from the other vector space corresponding to ANN shard  420  may be determined based on the vectors representing the common pages. As an example and not by way of limitation, P i,j  may be the vector representing common page i output by ANN shard j. A mapping of common page  1  from ANN shard  2  to ANN shard  1  may be the mapping P 1,1 =E 2 ×P 1,2 , where   may be a transformation that minimizes the error for the vectors representing the common pages from ANN shard  2  to ANN shard  1  (e.g., a transformation that minimizes a least square error). In particular embodiments, for each intermediate-page vector, a training-page vector may be generated by mapping the intermediate-page vector to the vector space using the determined mapping from other vector space corresponding to the other ANN that generated the intermediate-page vector to the vector space. Although this disclosure describes generating page vectors using a plurality of ANNs in a particular manner, this disclosure contemplates generating page vectors using a plurality of ANNs in any suitable manner. 
     In particular embodiments, social-networking system  660  may determine that the input vector representing the input post is located within a particular cluster in the vector space. In particular embodiments, social-networking system  660  may determine a topic of the input post based on the topic associated with the particular cluster that the input vector is located within. As an example and not by way of limitation, an input vector may represent a post comprising the text “watching the Seattle Mariners play against the Houston Astros #truetotheblue #sorryhouston”. Further, there may be 5,000 clusters in the vector space, associated with topics such as “restaurants,” “video games,” and “baseball.” Social-networking system  660  may determine that the input vector is located within a particular one of the 5,000 clusters in the vector space associated with the topic “baseball.” Although this disclosure describes determining a topic of an input post a particular manner, this disclosure contemplates determining a topic of an input post in any suitable manner. 
     In particular embodiments, determining a topic of the input post may comprise determining a representative label of the training pages located in the cluster associated with the topic. As an example and not by way of limitation, each cluster may be manually assigned a representative label by a user based on the training pages located in the cluster. In particular embodiments, each cluster may be automatically assigned a label based on an analysis of the training pages located within the cluster. As an example and not by way of limitation, a representative label may be determined for a cluster based on the one or more n-grams most frequent among the training pages location within the cluster. As another example and not by way of limitation, 500 training posts may be located in a particular cluster. The training posts in the cluster may include labels such as “Food snobs,” “food recipes,” “delicious eats,” and “burgers.” The most common n-gram among the labels of the training pages may be “food,” which may be determined as a representative label of the cluster. In particular embodiments, determining a topic of an input post may comprise determining that the vector representing the input post is located in a particular cluster without a representative label. In particular embodiments, determining the topic of a post may comprise determining a topic associated with a maximum probability value compared to other topics (e.g., the topic associated with i*=argmax i (T i ), where T i  may be the probability that the input post is related to topic i). Although this disclosure describes determining a topic in a particular manner, this disclosure contemplates determining a topic in any suitable manner. 
     In particular embodiments, social-networking system  660  may determine that a user is interacting with the input post. As an example and not by way of limitation, social-networking system  660  may determine that a user is viewing the input post, editing the input post, commenting on the input post, submitting the input post, or otherwise interacting with the input post. In particular embodiments, social-networking system  660  may provide, for display to the user, content associated with the topic of the input post. As an example and not by way of limitation, social-networking system  660  may determine that a user is viewing the input post and display recommended posts that have the same topic as the input post. As another example and not by way of limitation, social-networking system  660  may determine that the user has posted the input post and provide an advertisement for display to the user that corresponds to a vector in the same cluster as the input post. Although this disclosure describes determining user interaction and providing content for display to a user in a particular manner, this disclosure contemplates determining user interaction and providing content for display to a user in any suitable manner. 
     In particular embodiments, social-networking system  660  may rank the input post with respect to a user based at least in part on the determined topic of the input post. Social-networking system  660  may provide, for display to the user, the input post based on determining that the rank is at least a threshold rank. As an example and not by way of limitation, a user may be associated with a user profile. The user profile of the user may indicate that the user is interested in particular topics, and may indicate an intensity of interest in those topics. An input post may be ranked based on the determine topic of the input post (e.g., input posts with determined topics that the user is interested may be ranked higher than input posts with topics the user is not interested in). Although this disclosure describes ranking input posts based on a determined topic in a particular manner, this disclosure contemplates ranking input posts based on a determined topic in any suitable manner. 
     In particular embodiments, an input post may be a post on an online market place of a social network. As an example and not by way of limitation, the input post may be a post on an online market place regarding the sale of bedding. The input post may comprise the n-grams “Three piece down set for queen size bed” and an image of bedding on a bed. In particular embodiments, determining a topic of the input post using an ANN that was jointly trained based on a text vector and an image vector may have the advantage of accurately determining the topic where the n-grams and the image are not as semantically related. As an example and not by way of limitation, in the post regarding bedding for sale, if the topic were determined from the image vector alone, it may determine the topic as “bed” rather than “bedding.” Although this disclosure describes particular posts on a particular online marketplace, this disclosure contemplates any suitable post and any suitable online marketplace. Additionally, although this disclosure describes or illustrates particular embodiments as providing particular advantages, particular embodiments may provide none, some, or all of these advantages. 
       FIG. 5  illustrates an example method  500  for determining a topic of a post. The method may begin at step  510 , where social-networking system  660  may access an input vector representing an input post, wherein the input post comprises one or more n-grams and an image; the input vector corresponds to a point in a d-dimensional vector space; the input vector was generated by an artificial neural network (ANN) based on a text vector representing the one or more n-grams of the input post and an image vector representing the image of the input post; and the ANN was jointly trained to receive a text vector representing one or more n-grams of a post and an image vector representing an image of the post and then output a probability that the received post is related to the training posts of a training page. At step  520 , social-networking system  660  may determine a topic of the input post based on the input vector. Particular embodiments may repeat one or more steps of the method of  FIG. 5 , where appropriate. Although this disclosure describes and illustrates particular steps of the method of  FIG. 5  as occurring in a particular order, this disclosure contemplates any suitable steps of the method of  FIG. 5  occurring in any suitable order. Moreover, although this disclosure describes and illustrates an example method for determining a topic of a post including the particular steps of the method of  FIG. 5 , this disclosure contemplates any suitable method for determining a topic of a post including any suitable steps, which may include all, some, or none of the steps of the method of  FIG. 5 , where appropriate. Furthermore, although this disclosure describes and illustrates particular components, devices, or systems carrying out particular steps of the method of  FIG. 5 , this disclosure contemplates any suitable combination of any suitable components, devices, or systems carrying out any suitable steps of the method of  FIG. 5 . 
       FIG. 6  illustrates an example network environment  600  associated with a social-networking system. Network environment  600  includes a user  601 , a client system  630 , a social-networking system  660 , and a third-party system  670  connected to each other by a network  610 . Although  FIG. 6  illustrates a particular arrangement of user  601 , client system  630 , social-networking system  660 , third-party system  670 , and network  610 , this disclosure contemplates any suitable arrangement of user  601 , client system  630 , social-networking system  660 , third-party system  670 , and network  610 . As an example and not by way of limitation, two or more of client system  630 , social-networking system  660 , and third-party system  670  may be connected to each other directly, bypassing network  610 . As another example, two or more of client system  630 , social-networking system  660 , and third-party system  670  may be physically or logically co-located with each other in whole or in part. Moreover, although  FIG. 6  illustrates a particular number of users  601 , client systems  630 , social-networking systems  660 , third-party systems  670 , and networks  610 , this disclosure contemplates any suitable number of users  601 , client systems  630 , social-networking systems  660 , third-party systems  670 , and networks  610 . As an example and not by way of limitation, network environment  600  may include multiple users  601 , client system  630 , social-networking systems  660 , third-party systems  670 , and networks  610 . 
     In particular embodiments, user  601  may be an individual (human user), an entity (e.g., an enterprise, business, or third-party application), or a group (e.g., of individuals or entities) that interacts or communicates with or over social-networking system  660 . In particular embodiments, social-networking system  660  may be a network-addressable computing system hosting an online social network. Social-networking system  660  may generate, store, receive, and send social-networking data, such as, for example, user-profile data, concept-profile data, social-graph information, or other suitable data related to the online social network. Social-networking system  660  may be accessed by the other components of network environment  600  either directly or via network  610 . In particular embodiments, social-networking system  660  may include an authorization server (or other suitable component(s)) that allows users  601  to opt in to or opt out of having their actions logged by social-networking system  660  or shared with other systems (e.g., third-party systems  670 ), for example, by setting appropriate privacy settings. A privacy setting of a user may determine what information associated with the user may be logged, how information associated with the user may be logged, when information associated with the user may be logged, who may log information associated with the user, whom information associated with the user may be shared with, and for what purposes information associated with the user may be logged or shared. Authorization servers may be used to enforce one or more privacy settings of the users of social-networking system  30  through blocking, data hashing, anonymization, or other suitable techniques as appropriate. Third-party system  670  may be accessed by the other components of network environment  600  either directly or via network  610 . In particular embodiments, one or more users  601  may use one or more client systems  630  to access, send data to, and receive data from social-networking system  660  or third-party system  670 . Client system  630  may access social-networking system  660  or third-party system  670  directly, via network  610 , or via a third-party system. As an example and not by way of limitation, client system  630  may access third-party system  670  via social-networking system  660 . Client system  630  may be any suitable computing device, such as, for example, a personal computer, a laptop computer, a cellular telephone, a smartphone, a tablet computer, or an augmented/virtual reality device. 
     This disclosure contemplates any suitable network  610 . As an example and not by way of limitation, one or more portions of network  610  may include an ad hoc network, an intranet, an extranet, a virtual private network (VPN), a local area network (LAN), a wireless LAN (WLAN), a wide area network (WAN), a wireless WAN (WWAN), a metropolitan area network (MAN), a portion of the Internet, a portion of the Public Switched Telephone Network (PSTN), a cellular telephone network, or a combination of two or more of these. Network  610  may include one or more networks  610 . 
     Links  650  may connect client system  630 , social-networking system  660 , and third-party system  670  to communication network  610  or to each other. This disclosure contemplates any suitable links  650 . In particular embodiments, one or more links  650  include one or more wireline (such as for example Digital Subscriber Line (DSL) or Data Over Cable Service Interface Specification (DOC SIS)), wireless (such as for example Wi-Fi or Worldwide Interoperability for Microwave Access (WiMAX)), or optical (such as for example Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH)) links. In particular embodiments, one or more links  650  each include an ad hoc network, an intranet, an extranet, a VPN, a LAN, a WLAN, a WAN, a WWAN, a MAN, a portion of the Internet, a portion of the PSTN, a cellular technology-based network, a satellite communications technology-based network, another link  650 , or a combination of two or more such links  650 . Links  650  need not necessarily be the same throughout network environment  600 . One or more first links  650  may differ in one or more respects from one or more second links  650 . 
       FIG. 7  illustrates example social graph  700 . In particular embodiments, social-networking system  660  may store one or more social graphs  700  in one or more data stores. In particular embodiments, social graph  700  may include multiple nodes—which may include multiple user nodes  702  or multiple concept nodes  704 —and multiple edges  706  connecting the nodes. Example social graph  700  illustrated in  FIG. 7  is shown, for didactic purposes, in a two-dimensional visual map representation. In particular embodiments, a social-networking system  660 , client system  630 , or third-party system  670  may access social graph  700  and related social-graph information for suitable applications. The nodes and edges of social graph  700  may be stored as data objects, for example, in a data store (such as a social-graph database). Such a data store may include one or more searchable or queryable indexes of nodes or edges of social graph  700 . 
     In particular embodiments, a user node  702  may correspond to a user of social-networking system  660 . As an example and not by way of limitation, a user may be an individual (human user), an entity (e.g., an enterprise, business, or third-party application), or a group (e.g., of individuals or entities) that interacts or communicates with or over social-networking system  660 . In particular embodiments, when a user registers for an account with social-networking system  660 , social-networking system  660  may create a user node  702  corresponding to the user, and store the user node  702  in one or more data stores. Users and user nodes  702  described herein may, where appropriate, refer to registered users and user nodes  702  associated with registered users. In addition or as an alternative, users and user nodes  702  described herein may, where appropriate, refer to users that have not registered with social-networking system  660 . In particular embodiments, a user node  702  may be associated with information provided by a user or information gathered by various systems, including social-networking system  660 . As an example and not by way of limitation, a user may provide his or her name, profile picture, contact information, birth date, sex, marital status, family status, employment, education background, preferences, interests, or other demographic information. In particular embodiments, a user node  702  may be associated with one or more data objects corresponding to information associated with a user. In particular embodiments, a user node  702  may correspond to one or more webpages. 
     In particular embodiments, a concept node  704  may correspond to a concept. As an example and not by way of limitation, a concept may correspond to a place (such as, for example, a movie theater, restaurant, landmark, or city); a website (such as, for example, a website associated with social-network system  660  or a third-party website associated with a web-application server); an entity (such as, for example, a person, business, group, sports team, or celebrity); a resource (such as, for example, an audio file, video file, digital photo, text file, structured document, or application) which may be located within social-networking system  660  or on an external server, such as a web-application server; real or intellectual property (such as, for example, a sculpture, painting, movie, game, song, idea, photograph, or written work); a game; an activity; an idea or theory; an object in a augmented/virtual reality environment; another suitable concept; or two or more such concepts. A concept node  704  may be associated with information of a concept provided by a user or information gathered by various systems, including social-networking system  660 . As an example and not by way of limitation, information of a concept may include a name or a title; one or more images (e.g., an image of the cover page of a book); a location (e.g., an address or a geographical location); a website (which may be associated with a URL); contact information (e.g., a phone number or an email address); other suitable concept information; or any suitable combination of such information. In particular embodiments, a concept node  704  may be associated with one or more data objects corresponding to information associated with concept node  704 . In particular embodiments, a concept node  704  may correspond to one or more webpages. 
     In particular embodiments, a node in social graph  700  may represent or be represented by a webpage (which may be referred to as a “profile page”). Profile pages may be hosted by or accessible to social-networking system  660 . Profile pages may also be hosted on third-party websites associated with a third-party system  670 . As an example and not by way of limitation, a profile page corresponding to a particular external webpage may be the particular external webpage and the profile page may correspond to a particular concept node  704 . Profile pages may be viewable by all or a selected subset of other users. As an example and not by way of limitation, a user node  702  may have a corresponding user-profile page in which the corresponding user may add content, make declarations, or otherwise express himself or herself. As another example and not by way of limitation, a concept node  704  may have a corresponding concept-profile page in which one or more users may add content, make declarations, or express themselves, particularly in relation to the concept corresponding to concept node  704 . 
     In particular embodiments, a concept node  704  may represent a third-party webpage or resource hosted by a third-party system  670 . The third-party webpage or resource may include, among other elements, content, a selectable or other icon, or other inter-actable object (which may be implemented, for example, in JavaScript, AJAX, or PHP codes) representing an action or activity. As an example and not by way of limitation, a third-party webpage may include a selectable icon such as “like,” “check-in,” “eat,” “recommend,” or another suitable action or activity. A user viewing the third-party webpage may perform an action by selecting one of the icons (e.g., “check-in”), causing a client system  630  to send to social-networking system  660  a message indicating the user&#39;s action. In response to the message, social-networking system  660  may create an edge (e.g., a check-in-type edge) between a user node  702  corresponding to the user and a concept node  704  corresponding to the third-party webpage or resource and store edge  706  in one or more data stores. 
     In particular embodiments, a pair of nodes in social graph  700  may be connected to each other by one or more edges  706 . An edge  706  connecting a pair of nodes may represent a relationship between the pair of nodes. In particular embodiments, an edge  706  may include or represent one or more data objects or attributes corresponding to the relationship between a pair of nodes. As an example and not by way of limitation, a first user may indicate that a second user is a “friend” of the first user. In response to this indication, social-networking system  660  may send a “friend request” to the second user. If the second user confirms the “friend request,” social-networking system  660  may create an edge  706  connecting the first user&#39;s user node  702  to the second user&#39;s user node  702  in social graph  700  and store edge  706  as social-graph information in one or more of data stores  664 . In the example of  FIG. 7 , social graph  700  includes an edge  706  indicating a friend relation between user nodes  702  of user “A” and user “B” and an edge indicating a friend relation between user nodes  702  of user “C” and user “B.” Although this disclosure describes or illustrates particular edges  706  with particular attributes connecting particular user nodes  702 , this disclosure contemplates any suitable edges  706  with any suitable attributes connecting user nodes  702 . As an example and not by way of limitation, an edge  706  may represent a friendship, family relationship, business or employment relationship, fan relationship (including, e.g., liking, etc.), follower relationship, visitor relationship (including, e.g., accessing, viewing, checking-in, sharing, etc.), subscriber relationship, superior/subordinate relationship, reciprocal relationship, non-reciprocal relationship, another suitable type of relationship, or two or more such relationships. Moreover, although this disclosure generally describes nodes as being connected, this disclosure also describes users or concepts as being connected. Herein, references to users or concepts being connected may, where appropriate, refer to the nodes corresponding to those users or concepts being connected in social graph  700  by one or more edges  706 . 
     In particular embodiments, an edge  706  between a user node  702  and a concept node  704  may represent a particular action or activity performed by a user associated with user node  702  toward a concept associated with a concept node  704 . As an example and not by way of limitation, as illustrated in  FIG. 7 , a user may “like,” “attended,” “played,” “listened,” “cooked,” “worked at,” or “watched” a concept, each of which may correspond to an edge type or subtype. A concept-profile page corresponding to a concept node  704  may include, for example, a selectable “check in” icon (such as, for example, a clickable “check in” icon) or a selectable “add to favorites” icon. Similarly, after a user clicks these icons, social-networking system  660  may create a “favorite” edge or a “check in” edge in response to a user&#39;s action corresponding to a respective action. As another example and not by way of limitation, a user (user “C”) may listen to a particular song (“Imagine”) using a particular application (SPOTIFY, which is an online music application). In this case, social-networking system  660  may create a “listened” edge  706  and a “used” edge (as illustrated in  FIG. 7 ) between user nodes  702  corresponding to the user and concept nodes  704  corresponding to the song and application to indicate that the user listened to the song and used the application. Moreover, social-networking system  660  may create a “played” edge  706  (as illustrated in  FIG. 7 ) between concept nodes  704  corresponding to the song and the application to indicate that the particular song was played by the particular application. In this case, “played” edge  706  corresponds to an action performed by an external application (SPOTIFY) on an external audio file (the song “Imagine”). Although this disclosure describes particular edges  706  with particular attributes connecting user nodes  702  and concept nodes  704 , this disclosure contemplates any suitable edges  706  with any suitable attributes connecting user nodes  702  and concept nodes  704 . Moreover, although this disclosure describes edges between a user node  702  and a concept node  704  representing a single relationship, this disclosure contemplates edges between a user node  702  and a concept node  704  representing one or more relationships. As an example and not by way of limitation, an edge  706  may represent both that a user likes and has used at a particular concept. Alternatively, another edge  706  may represent each type of relationship (or multiples of a single relationship) between a user node  702  and a concept node  704  (as illustrated in  FIG. 7  between user node  702  for user “E” and concept node  704  for “SPOTIFY”). 
     In particular embodiments, social-networking system  660  may create an edge  706  between a user node  702  and a concept node  704  in social graph  700 . As an example and not by way of limitation, a user viewing a concept-profile page (such as, for example, by using a web browser or a special-purpose application hosted by the user&#39;s client system  630 ) may indicate that he or she likes the concept represented by the concept node  704  by clicking or selecting a “Like” icon, which may cause the user&#39;s client system  630  to send to social-networking system  660  a message indicating the user&#39;s liking of the concept associated with the concept-profile page. In response to the message, social-networking system  660  may create an edge  706  between user node  702  associated with the user and concept node  704 , as illustrated by “like” edge  706  between the user and concept node  704 . In particular embodiments, social-networking system  660  may store an edge  706  in one or more data stores. In particular embodiments, an edge  706  may be automatically formed by social-networking system  660  in response to a particular user action. As an example and not by way of limitation, if a first user uploads a picture, watches a movie, or listens to a song, an edge  706  may be formed between user node  702  corresponding to the first user and concept nodes  704  corresponding to those concepts. Although this disclosure describes forming particular edges  706  in particular manners, this disclosure contemplates forming any suitable edges  706  in any suitable manner. 
     In particular embodiments, social-networking system  660  may determine the social-graph affinity (which may be referred to herein as “affinity”) of various social-graph entities for each other. Affinity may represent the strength of a relationship or level of interest between particular objects associated with the online social network, such as users, concepts, content, actions, advertisements, other objects associated with the online social network, or any suitable combination thereof. Affinity may also be determined with respect to objects associated with third-party systems  670  or other suitable systems. An overall affinity for a social-graph entity for each user, subject matter, or type of content may be established. The overall affinity may change based on continued monitoring of the actions or relationships associated with the social-graph entity. Although this disclosure describes determining particular affinities in a particular manner, this disclosure contemplates determining any suitable affinities in any suitable manner. 
     In particular embodiments, social-networking system  660  may measure or quantify social-graph affinity using an affinity coefficient (which may be referred to herein as “coefficient”). The coefficient may represent or quantify the strength of a relationship between particular objects associated with the online social network. The coefficient may also represent a probability or function that measures a predicted probability that a user will perform a particular action based on the user&#39;s interest in the action. In this way, a user&#39;s future actions may be predicted based on the user&#39;s prior actions, where the coefficient may be calculated at least in part on the history of the user&#39;s actions. Coefficients may be used to predict any number of actions, which may be within or outside of the online social network. As an example and not by way of limitation, these actions may include various types of communications, such as sending messages, posting content, or commenting on content; various types of observation actions, such as accessing or viewing profile pages, media, or other suitable content; various types of coincidence information about two or more social-graph entities, such as being in the same group, tagged in the same photograph, checked-in at the same location, or attending the same event; or other suitable actions. Although this disclosure describes measuring affinity in a particular manner, this disclosure contemplates measuring affinity in any suitable manner. 
     In particular embodiments, social-networking system  660  may use a variety of factors to calculate a coefficient. These factors may include, for example, user actions, types of relationships between objects, location information, other suitable factors, or any combination thereof. In particular embodiments, different factors may be weighted differently when calculating the coefficient. The weights for each factor may be static or the weights may change according to, for example, the user, the type of relationship, the type of action, the user&#39;s location, and so forth. Ratings for the factors may be combined according to their weights to determine an overall coefficient for the user. As an example and not by way of limitation, particular user actions may be assigned both a rating and a weight while a relationship associated with the particular user action is assigned a rating and a correlating weight (e.g., so the weights total 100%). To calculate the coefficient of a user towards a particular object, the rating assigned to the user&#39;s actions may comprise, for example, 60% of the overall coefficient, while the relationship between the user and the object may comprise 40% of the overall coefficient. In particular embodiments, the social-networking system  660  may consider a variety of variables when determining weights for various factors used to calculate a coefficient, such as, for example, the time since information was accessed, decay factors, frequency of access, relationship to information or relationship to the object about which information was accessed, relationship to social-graph entities connected to the object, short- or long-term averages of user actions, user feedback, other suitable variables, or any combination thereof. As an example and not by way of limitation, a coefficient may include a decay factor that causes the strength of the signal provided by particular actions to decay with time, such that more recent actions are more relevant when calculating the coefficient. The ratings and weights may be continuously updated based on continued tracking of the actions upon which the coefficient is based. Any type of process or algorithm may be employed for assigning, combining, averaging, and so forth the ratings for each factor and the weights assigned to the factors. In particular embodiments, social-networking system  660  may determine coefficients using machine-learning algorithms trained on historical actions and past user responses, or data farmed from users by exposing them to various options and measuring responses. Although this disclosure describes calculating coefficients in a particular manner, this disclosure contemplates calculating coefficients in any suitable manner. 
     In particular embodiments, social-networking system  660  may calculate a coefficient based on a user&#39;s actions. Social-networking system  660  may monitor such actions on the online social network, on a third-party system  670 , on other suitable systems, or any combination thereof. Any suitable type of user actions may be tracked or monitored. Typical user actions include viewing profile pages, creating or posting content, interacting with content, tagging or being tagged in images, joining groups, listing and confirming attendance at events, checking-in at locations, liking particular pages, creating pages, and performing other tasks that facilitate social action. In particular embodiments, social-networking system  660  may calculate a coefficient based on the user&#39;s actions with particular types of content. The content may be associated with the online social network, a third-party system  670 , or another suitable system. The content may include users, profile pages, posts, news stories, headlines, instant messages, chat room conversations, emails, advertisements, pictures, video, music, other suitable objects, or any combination thereof. Social-networking system  660  may analyze a user&#39;s actions to determine whether one or more of the actions indicate an affinity for subject matter, content, other users, and so forth. As an example and not by way of limitation, if a user frequently posts content related to “coffee” or variants thereof, social-networking system  660  may determine the user has a high coefficient with respect to the concept “coffee”. Particular actions or types of actions may be assigned a higher weight and/or rating than other actions, which may affect the overall calculated coefficient. As an example and not by way of limitation, if a first user emails a second user, the weight or the rating for the action may be higher than if the first user simply views the user-profile page for the second user. 
     In particular embodiments, social-networking system  660  may calculate a coefficient based on the type of relationship between particular objects. Referencing the social graph  700 , social-networking system  660  may analyze the number and/or type of edges  706  connecting particular user nodes  702  and concept nodes  704  when calculating a coefficient. As an example and not by way of limitation, user nodes  702  that are connected by a spouse-type edge (representing that the two users are married) may be assigned a higher coefficient than a user nodes  702  that are connected by a friend-type edge. In other words, depending upon the weights assigned to the actions and relationships for the particular user, the overall affinity may be determined to be higher for content about the user&#39;s spouse than for content about the user&#39;s friend. In particular embodiments, the relationships a user has with another object may affect the weights and/or the ratings of the user&#39;s actions with respect to calculating the coefficient for that object. As an example and not by way of limitation, if a user is tagged in a first photo, but merely likes a second photo, social-networking system  660  may determine that the user has a higher coefficient with respect to the first photo than the second photo because having a tagged-in-type relationship with content may be assigned a higher weight and/or rating than having a like-type relationship with content. In particular embodiments, social-networking system  660  may calculate a coefficient for a first user based on the relationship one or more second users have with a particular object. In other words, the connections and coefficients other users have with an object may affect the first user&#39;s coefficient for the object. As an example and not by way of limitation, if a first user is connected to or has a high coefficient for one or more second users, and those second users are connected to or have a high coefficient for a particular object, social-networking system  660  may determine that the first user should also have a relatively high coefficient for the particular object. In particular embodiments, the coefficient may be based on the degree of separation between particular objects. The lower coefficient may represent the decreasing likelihood that the first user will share an interest in content objects of the user that is indirectly connected to the first user in the social graph  700 . As an example and not by way of limitation, social-graph entities that are closer in the social graph  700  (i.e., fewer degrees of separation) may have a higher coefficient than entities that are further apart in the social graph  700 . 
     In particular embodiments, social-networking system  660  may calculate a coefficient based on location information. Objects that are geographically closer to each other may be considered to be more related or of more interest to each other than more distant objects. In particular embodiments, the coefficient of a user towards a particular object may be based on the proximity of the object&#39;s location to a current location associated with the user (or the location of a client system  630  of the user). A first user may be more interested in other users or concepts that are closer to the first user. As an example and not by way of limitation, if a user is one mile from an airport and two miles from a gas station, social-networking system  660  may determine that the user has a higher coefficient for the airport than the gas station based on the proximity of the airport to the user. 
     In particular embodiments, social-networking system  660  may perform particular actions with respect to a user based on coefficient information. Coefficients may be used to predict whether a user will perform a particular action based on the user&#39;s interest in the action. A coefficient may be used when generating or presenting any type of objects to a user, such as advertisements, search results, news stories, media, messages, notifications, or other suitable objects. The coefficient may also be utilized to rank and order such objects, as appropriate. In this way, social-networking system  660  may provide information that is relevant to user&#39;s interests and current circumstances, increasing the likelihood that they will find such information of interest. In particular embodiments, social-networking system  660  may generate content based on coefficient information. Content objects may be provided or selected based on coefficients specific to a user. As an example and not by way of limitation, the coefficient may be used to generate media for the user, where the user may be presented with media for which the user has a high overall coefficient with respect to the media object. As another example and not by way of limitation, the coefficient may be used to generate advertisements for the user, where the user may be presented with advertisements for which the user has a high overall coefficient with respect to the advertised object. In particular embodiments, social-networking system  660  may generate search results based on coefficient information. Search results for a particular user may be scored or ranked based on the coefficient associated with the search results with respect to the querying user. As an example and not by way of limitation, search results corresponding to objects with higher coefficients may be ranked higher on a search-results page than results corresponding to objects having lower coefficients. 
     In particular embodiments, social-networking system  660  may calculate a coefficient in response to a request for a coefficient from a particular system or process. To predict the likely actions a user may take (or may be the subject of) in a given situation, any process may request a calculated coefficient for a user. The request may also include a set of weights to use for various factors used to calculate the coefficient. This request may come from a process running on the online social network, from a third-party system  670  (e.g., via an API or other communication channel), or from another suitable system. In response to the request, social-networking system  660  may calculate the coefficient (or access the coefficient information if it has previously been calculated and stored). In particular embodiments, social-networking system  660  may measure an affinity with respect to a particular process. Different processes (both internal and external to the online social network) may request a coefficient for a particular object or set of objects. Social-networking system  660  may provide a measure of affinity that is relevant to the particular process that requested the measure of affinity. In this way, each process receives a measure of affinity that is tailored for the different context in which the process will use the measure of affinity. 
     In connection with social-graph affinity and affinity coefficients, particular embodiments may utilize one or more systems, components, elements, functions, methods, operations, or steps disclosed in U.S. patent application Ser. No. 11/503,093, filed 11 Aug. 2006, U.S. patent application Ser. No. 12/977,027, filed 22 Dec. 2010, U.S. patent application Ser. No. 12/978,265, filed 23 Dec. 2010, and U.S. patent application Ser. No. 13/632,869, filed 1 Oct. 2012, each of which is incorporated by reference. 
       FIG. 8  illustrates an example computer system  800 . In particular embodiments, one or more computer systems  800  perform one or more steps of one or more methods described or illustrated herein. In particular embodiments, one or more computer systems  800  provide functionality described or illustrated herein. In particular embodiments, software running on one or more computer systems  800  performs one or more steps of one or more methods described or illustrated herein or provides functionality described or illustrated herein. Particular embodiments include one or more portions of one or more computer systems  800 . Herein, reference to a computer system may encompass a computing device, and vice versa, where appropriate. Moreover, reference to a computer system may encompass one or more computer systems, where appropriate. 
     This disclosure contemplates any suitable number of computer systems  800 . This disclosure contemplates computer system  800  taking any suitable physical form. As example and not by way of limitation, computer system  800  may be an embedded computer system, a system-on-chip (SOC), a single-board computer system (SBC) (such as, for example, a computer-on-module (COM) or system-on-module (SOM)), a desktop computer system, a laptop or notebook computer system, an interactive kiosk, a mainframe, a mesh of computer systems, a mobile telephone, a personal digital assistant (PDA), a server, a tablet computer system, an augmented/virtual reality device, or a combination of two or more of these. Where appropriate, computer system  800  may include one or more computer systems  800 ; be unitary or distributed; span multiple locations; span multiple machines; span multiple data centers; or reside in a cloud, which may include one or more cloud components in one or more networks. Where appropriate, one or more computer systems  800  may perform without substantial spatial or temporal limitation one or more steps of one or more methods described or illustrated herein. As an example and not by way of limitation, one or more computer systems  800  may perform in real time or in batch mode one or more steps of one or more methods described or illustrated herein. One or more computer systems  800  may perform at different times or at different locations one or more steps of one or more methods described or illustrated herein, where appropriate. 
     In particular embodiments, computer system  800  includes a processor  802 , memory  804 , storage  806 , an input/output (I/O) interface  808 , a communication interface  810 , and a bus  812 . Although this disclosure describes and illustrates a particular computer system having a particular number of particular components in a particular arrangement, this disclosure contemplates any suitable computer system having any suitable number of any suitable components in any suitable arrangement. 
     In particular embodiments, processor  802  includes hardware for executing instructions, such as those making up a computer program. As an example and not by way of limitation, to execute instructions, processor  802  may retrieve (or fetch) the instructions from an internal register, an internal cache, memory  804 , or storage  806 ; decode and execute them; and then write one or more results to an internal register, an internal cache, memory  804 , or storage  806 . In particular embodiments, processor  802  may include one or more internal caches for data, instructions, or addresses. This disclosure contemplates processor  802  including any suitable number of any suitable internal caches, where appropriate. As an example and not by way of limitation, processor  802  may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory  804  or storage  806 , and the instruction caches may speed up retrieval of those instructions by processor  802 . Data in the data caches may be copies of data in memory  804  or storage  806  for instructions executing at processor  802  to operate on; the results of previous instructions executed at processor  802  for access by subsequent instructions executing at processor  802  or for writing to memory  804  or storage  806 ; or other suitable data. The data caches may speed up read or write operations by processor  802 . The TLBs may speed up virtual-address translation for processor  802 . In particular embodiments, processor  802  may include one or more internal registers for data, instructions, or addresses. This disclosure contemplates processor  802  including any suitable number of any suitable internal registers, where appropriate. Where appropriate, processor  802  may include one or more arithmetic logic units (ALUs); be a multi-core processor; or include one or more processors  802 . Although this disclosure describes and illustrates a particular processor, this disclosure contemplates any suitable processor. 
     [ 64 ] In particular embodiments, memory  804  includes main memory for storing instructions for processor  802  to execute or data for processor  802  to operate on. As an example and not by way of limitation, computer system  800  may load instructions from storage  806  or another source (such as, for example, another computer system  800 ) to memory  804 . Processor  802  may then load the instructions from memory  804  to an internal register or internal cache. To execute the instructions, processor  802  may retrieve the instructions from the internal register or internal cache and decode them. During or after execution of the instructions, processor  802  may write one or more results (which may be intermediate or final results) to the internal register or internal cache. Processor  802  may then write one or more of those results to memory  804 . In particular embodiments, processor  802  executes only instructions in one or more internal registers or internal caches or in memory  804  (as opposed to storage  806  or elsewhere) and operates only on data in one or more internal registers or internal caches or in memory  804  (as opposed to storage  806  or elsewhere). One or more memory buses (which may each include an address bus and a data bus) may couple processor  802  to memory  804 . Bus  812  may include one or more memory buses, as described below. In particular embodiments, one or more memory management units (MMUs) reside between processor  802  and memory  804  and facilitate accesses to memory  804  requested by processor  802 . In particular embodiments, memory  804  includes random access memory (RAM). This RAM may be volatile memory, where appropriate. Where appropriate, this RAM may be dynamic RAM (DRAM) or static RAM (SRAM). Moreover, where appropriate, this RAM may be single-ported or multi-ported RAM. This disclosure contemplates any suitable RAM. Memory  804  may include one or more memories  804 , where appropriate. Although this disclosure describes and illustrates particular memory, this disclosure contemplates any suitable memory. 
     In particular embodiments, storage  806  includes mass storage for data or instructions. As an example and not by way of limitation, storage  806  may include a hard disk drive (HDD), a floppy disk drive, flash memory, an optical disc, a magneto-optical disc, magnetic tape, or a Universal Serial Bus (USB) drive or a combination of two or more of these. Storage  806  may include removable or non-removable (or fixed) media, where appropriate. Storage  806  may be internal or external to computer system  800 , where appropriate. In particular embodiments, storage  806  is non-volatile, solid-state memory. In particular embodiments, storage  806  includes read-only memory (ROM). Where appropriate, this ROM may be mask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory or a combination of two or more of these. This disclosure contemplates mass storage  806  taking any suitable physical form. Storage  806  may include one or more storage control units facilitating communication between processor  802  and storage  806 , where appropriate. Where appropriate, storage  806  may include one or more storages  806 . Although this disclosure describes and illustrates particular storage, this disclosure contemplates any suitable storage. 
     In particular embodiments, I/O interface  808  includes hardware, software, or both, providing one or more interfaces for communication between computer system  800  and one or more I/O devices. Computer system  800  may include one or more of these I/O devices, where appropriate. One or more of these I/O devices may enable communication between a person and computer system  800 . As an example and not by way of limitation, an I/O device may include a keyboard, keypad, microphone, monitor, mouse, printer, scanner, speaker, still camera, stylus, tablet, touch screen, trackball, video camera, another suitable I/O device or a combination of two or more of these. An I/O device may include one or more sensors. This disclosure contemplates any suitable I/O devices and any suitable I/O interfaces  808  for them. Where appropriate, I/O interface  808  may include one or more device or software drivers enabling processor  802  to drive one or more of these I/O devices. I/O interface  808  may include one or more I/O interfaces  808 , where appropriate. Although this disclosure describes and illustrates a particular I/O interface, this disclosure contemplates any suitable I/O interface. 
     In particular embodiments, communication interface  810  includes hardware, software, or both providing one or more interfaces for communication (such as, for example, packet-based communication) between computer system  800  and one or more other computer systems  800  or one or more networks. As an example and not by way of limitation, communication interface  810  may include a network interface controller (NIC) or network adapter for communicating with an Ethernet or other wire-based network or a wireless NIC (WNIC) or wireless adapter for communicating with a wireless network, such as a WI-FI network. This disclosure contemplates any suitable network and any suitable communication interface  810  for it. As an example and not by way of limitation, computer system  800  may communicate with an ad hoc network, a personal area network (PAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), or one or more portions of the Internet or a combination of two or more of these. One or more portions of one or more of these networks may be wired or wireless. As an example, computer system  800  may communicate with a wireless PAN (WPAN) (such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WI-MAX network, a cellular telephone network (such as, for example, a Global System for Mobile Communications (GSM) network), or other suitable wireless network or a combination of two or more of these. Computer system  800  may include any suitable communication interface  810  for any of these networks, where appropriate. Communication interface  810  may include one or more communication interfaces  810 , where appropriate. Although this disclosure describes and illustrates a particular communication interface, this disclosure contemplates any suitable communication interface. 
     In particular embodiments, bus  812  includes hardware, software, or both coupling components of computer system  800  to each other. As an example and not by way of limitation, bus  812  may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCIe) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or another suitable bus or a combination of two or more of these. Bus  812  may include one or more buses  812 , where appropriate. Although this disclosure describes and illustrates a particular bus, this disclosure contemplates any suitable bus or interconnect. 
     Herein, a computer-readable non-transitory storage medium or media may include one or more semiconductor-based or other integrated circuits (ICs) (such, as for example, field-programmable gate arrays (FPGAs) or application-specific ICs (ASICs)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs), magneto-optical discs, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid-state drives (SSDs), RAM-drives, SECURE DIGITAL cards or drives, any other suitable computer-readable non-transitory storage media, or any suitable combination of two or more of these, where appropriate. A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate. 
     Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context. 
     The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Additionally, although this disclosure describes or illustrates particular embodiments as providing particular advantages, particular embodiments may provide none, some, or all of these advantages.