Talk:Radix tree

message: I have added a simple diagram (and I removed reqdiagram) . User:rocchini 2007-05-17
The nice diagram given at the front gives the misleading impression that each node always has two children.  That would be true if you branch on bits; but if branching on characters there can be as many children as there are letters in your character set. Bhyde (talk) 15:52, 13 March 2010 (UTC)
thread_title:  Diagram 

message: The second diagram depicts a structure that is not a tree.  It is also not a trie, prefix tree, or radix tree.  The article provides no explanation for the image.  68.191.211.204 (talk) 13:44, 15 December 2009 (UTC)
thread_title:  Second Diagram 

message: This article should be named "Radix trie" not "Radix tree", because Patricia tries and radix tries are tries, not (search) trees.  This article never once mentions that Patricia tries are also called Radix-2 tries.  Indeed, the article never once mentions why radix tries are called radix tries:  you can choose binary, quaternary, octary, and so forth through the higher-order powers of two radixes. At each node you can diverge to two children via the 2 values of the next 1 bit (i.e., Patricia trie = Radix-2 trie) or you can diverge to four children via 4 values of the next 2 bits (i.e., Radix-4 trie) or you can diverge to eight children via 8 values of the next 4 bits (i.e., Radix-8 trie).  This article does not clearly present the fact that the entire concept of the Internet's routing is based on radix tries, especially inter-autonomous-system protocols such as BGP. —optikos (talk) 06:38, 5 May 2010 (UTC)
replies: text: Rather, one should ask why a mostly *unrelated* tree structure has been injected into this article. Crit-bit trees are **not** tries, but an optimized flavour of binary search trees. A crit-bit tree is a binary search tree which only branches at every bit position where two subsets of previously inserted keys differed, according to the bit's value in the newly inserted key. Unlike a trie, it therefore does not contain the full key in its structure (it is perfectly possible, and valid, for a key to differ in one or several bits with any previously seen key, before the "critical" bit) and needs to store the key in leaf nodes for an unambiguous lookup.  — Preceding unsigned comment added by 92.192.19.64 (talk) 14:32, 24 July 2012 (UTC)
thread_title:  Nomenclature 

message: According to the original paper defining PATRICIA, published by DR Morrison in October 1968s "Journal of the ACM", PATRICIA is a type of radix tree, but not all radix trees are PATRICIA trees. Two highly reputable academic resources implement a very specific algorithm which doesn't stray at all from the ACM article. It seems incorrect to suggest that radix trees are also known as PATRICIA trees, so I'm removing that reference. Sebivor (talk) 07:34, 15 July 2015 (UTC)
replies: text: There still is a picture that describes Patricia tries. It would be great if the relationship to this kind of tries would be explained so that that name doesn't come from nowhere. --2001:16B8:6849:9A00:259E:59E7:BFFF:1D38 (talk)  —Preceding undated comment added 08:42, 8 January 2020 (UTC)
thread_title:  Invalid association of PATRICIA 

message: The article currently says they have at LEAST radix children per node, but I really don't see how can they have more than radix, and the diagram certainly shows less than radix children per node.79.183.100.150 (talk) 09:55, 20 February 2016 (UTC)
replies: text: I agree. The graph captioned "Insert 'slower' while keeping 'slow'" breaks this. I also find the talk of "the radix" of a radix tree quite confusing. What is the "radix" of a radix tree? It's not defined anywhere. Lookup radix, you find "base", look for the equivalent in a tree, you find binary tree, you find the K-ary tree article, which means "at most K chilren per node", but you never see the word "base" or "radix". And this sentence makes no sense: "where the quantity of bits in that chunk at that node is the radix r of the radix trie." ..., huh? I see no examples of quantity of bits in a node having anything to do with radix. None of this seems to belong in the summary either, if you look at non-wikipedia sources of radix trees, I didn't run into a single one which even mentions the "radix." 73.53.70.213 (talk) 04:49, 16 December 2016 (UTC)
thread_title:  Don't radix tries have at MOST radix children per node? 

message: "When r is an integer power of 2 greater or equal to 4, then the radix trie is an r-ary trie, which lessens the depth of the radix trie at the expense of potential sparseness."
It would be great to close the loop here with the example tree in the first illustration.   Is it a 5-ary trie since the largest key is 5 chars?   The article uses 'bits' somewhat loosely, as presumably the keys here are characters, which are 7 bits in ASCII encoding, not one.   I find this article a bit puzzling, and wish an expert would clarify!
-- Alison Chaiken
Alison Chaiken (talk) 17:11, 11 March 2017 (UTC)
thread_title:  please tie the text better to the example 

message: The text and the operation in diagram meant to indicate that word "test" is already in the tree and the word "team" is being inserted afterward. However, it is mistakenly written into Diagram that word "test" is being inserted. Please edit the diagram and change it to "team". Bossudenotredame (talk) 12:59, 28 September 2018 (UTC)
thread_title:  Operation/Insertion Diagram 

message: I came here looking for a precise and concise description of PATRICIA, and finding nothing really, I decided to write it myself and add it to the "Variants" section. I first implemented PATRICIA back in the 1980s, and I remember having access to a wonderfully clear description back then, complete with diagrams. Unfortunately I can no longer remember what that book was - I can't find it in Knuth or Wirth. It might have been Sedgewick. In the meantime I've referenced Morrison's original article in ACM.
:The Description of PATRICIA is now reads as PATRICIA is a special variant of radix - 2 trie which is radix - 2 trie :-/ the definition given for PATRICIA is equivalent to the definition of radix - 2 trie. If we only include nodes we remove lonely middle nodes then we end up with a trie with only branch nodes which PATRICIA definition is trying to explain. Bossudenotredame (talk) 17:33, 1 May 2024 (UTC)
thread_title:  Description of PATRICIA added. 

message: The summary starts with this sentence: "In computer science, a radix tree (also radix trie or compact prefix tree) is a data structure that represents a space-optimized trie (prefix tree) in which each node that is the only child is merged with its parent."
I have been unable to track down any references for this definition, and it is IMHO inaccurate. The term "radix" references radix sort, and I fail to see how path compaction has anything to do with the number of elements in the alphabet or the arity of the tree. Is it possible for the original author to provide references for this section? Wppds (talk) 07:29, 22 March 2019 (UTC)
thread_title:  Summary references 

message: The sentence "[t]he result is that the number of children of every internal node is at most the radix r of the radix tree" appears to make the claim that its stated fact follows from the preceding claim "each node that is the only child is merged with its parent".
This is not so; if we "decompress" the tree such that the merged parents are split into only children and grandchildren, the tree still has the at-most-r property.
Furthermore, radix trees are not all compressed this way.
There are radix trees which can be navigated by breaking a (typically numeric) key into pieces (typically bit fields). Each piece directly selects a child. An example of this is the page directory structure of a virtual memory system. KazKylheku (talk) 16:01, 1 February 2022 (UTC)
thread_title:  Does not follow.