Communication control system between parallel computers

Abstract: A communication control system between parallel computers performs a broadcast communication in a network between parallel computer nodes and comprises destination detecting unit (13) for detecting the destination information designating the scope of the destination nodes from the data; between-node distance processing unit (14) for obtaining the distance between the particular computer node and the destination computer node, based on the destination information; and destination judgment unit (15) for judging whether the data should be obtained by the self node, for judging, whether the data should be further transmitted to the other node and for determining the direction of the transmission, based on the distance information.

Description: Background of the Invention (a) Field of the Invention The present invention relates to a communication system of parallel computers in a field of a multi-processor system i,e., MIMD (multiple instruction stream multiple data stream) in which a plurality of programs operate in parallel and more particularly to a communication in a network between parallel computers connected in N-dimensional torus connection (in which one end node is connected to the other end node) or N-dimensional matrix connection where a broadcast communication or a simultaneous communication for simultaneously transmitting the same content to many receiving nodes by designating the scope of the destinated nodes. (b) Related Art A conventional communication system for performing a broadcast communication is shown in Figure 1. This system transmits data by designating the coordinate ID of the destination nodes. A receiving process unit 1 receives data transmitted from other nodes and a destination detection unit 2 detects the destination coordinate of the data. A destination judgment unit 3 judges whether the destination coordinate is the self (or local) node or other node and obtains the data when the destination coordinate designates the self node. A transmission process unit 4 transmits the data to the other node if the destination coordinate is for the other node. In a network of parallel computers connected in two-dimension torus connection as shown in Figure 2, when the data is transmitted from transmitting node N61 to receiving node N67, the transmission data designates the coordinate of receiving node N67 and the data transmitted from node N61 is transferred to node N67 by being relayed via nodes N62 and N63. Respective receiving nodes can only relay or receive the data. Therefore, as shown in Figure 3, the present network performs a broadcast communication from node N76 to nodes N71, N72, N73, N75, N77, N79, N710 and N711 as follows. A process of (1) data transmission from node N76 to node N71, (2) data transmission from node N76 to node N72, (3) data transmission from node N76 to node N73, (4) data transmission from node N76 to node N75, (5) data transmission from node N76 to node N77, (6) data transmission from node N76 to node N79, (7) data transmission from node N76 to node N710 and (8) data transmission from node N76 to node N711 is repeated. Therefore, in the above recited method, node N76 transmits the data to respective nodes eight times. In the prior art, where a communication is performed between parallel computers connected in a torus connection, the coordinates of the destination nodes are designated in the data and the transmitted data is merely relayed by the nodes on the way and is transmitted to the destination receiving node. Therefore, where a broadcast communication is performed, the transmission source node repeats the data transmission at times corresponding to the number of the receiving node. Where the same message is transmitted from a node to a plurality of other nodes, namely, where a broadcast communication is performed, a transmission is repeated so that the message is transmitted from one node to a plurality of other nodes one by one. Therefore, there is a problem that the broadcast communication cannot be performed with high speed and high efficiency. Further, in the prior art, the control of the node for relaying the data which is performed by designating the coordinates is complex. Summary of the Invention EP-A-0 132 926 discloses a communication control system having the features of the preamble of accompanying claim 1. In this system, the data being transmitted has an address specifying a unique destination node (terminal). DISTRIBUTED COMPUTING, vol.1, no.4, October 1986, Berlin, Germany, pages 187-196, discloses a communication control system also requiring an address specifying a unique destination node. Such systems have the drawback that if the same data is to be transmitted to each of N destination nodes, an address must be specified N times. According to the present invention, there is provided a communication control system between parallel computers for performing a broadcast communication in a network between parallel nodes, in which each of said nodes comprises: data receiving means for receiving the data transmitted from other nodes in respective directions; destination detecting means for detecting destination information from the data; between-node distance processing means for obtaining distance information between a particular computer node and the destination node, based on the destination information; destination judgement means for judging whether the data should be obtained by a local node, for judging, whether the data should be further transmitted to another node and for determining a direction of the transmission, based on the distance information; and transmitting process means for transmitting the data whose destination is judged, with regard to a particular direction; characterised in that: said destination information designates a scope of destination nodes for the data, and in that said transmitting process means are arranged to transmit the data to all other nodes within said scope. Thus, the present invention provides a communication system between parallel computers capable of performing a broadcast communication designating the scope of the destination nodes. In an embodiment of the present invention, the broadcast communication is performed by worm-hole routing with high speed and high efficiency by transmitting the message divided into flits each constituting a unit of data transmission. A header flit selected from the flits is given the destination information specifying the scope of the broadcast transmission, thereby enabling a receiving node to refer to the scope information to preserve the message in the same node and to transmit the message to all other nodes within the scope. Reference is made by way of example, to the accompanying drawings in which: Figure 1 shows a block diagram of the prior art communication system, Figure 2 shows an example of the prior art communication system used for two-dimensional torus-connection nodes, Figure 3 shows another example of the prior art of torus connection nodes, Figure 4 shows a block diagram showing the principle of the present invention, Figure 5A shows a block diagram of a one-dimensional network, Figure 5B shows a block diagram of a two-dimensional network, Figure 5C shows an embodiment of a data-flit used in the present invention, Figures 6A and 6B show a flowchart of another embodiment of the present invention Figure 7A shows a block diagram of a routing in both the X and Y directions, Figure 7B shows a block diagram of the whole structure of a plurality of nodes connected in parallel, Figure 8 shows a block diagram of an embodiment of the present invention, Figure 9 shows an explanatory view of the embodiment of the present invention, Figures 10A to 10E shows the process flow of a receiving node in the present embodiment. Figure 11A shows an embodiment in which the scope of the destination is shifted in one direction, and Figure 11B shows a flowchart used in the transmitting node in the embodiment shown in Figure 11A, Figure 12A shows an embodiment in which the scope of the destination does not include the transmission node, and Figure 12B shows a flowchart for use in a transmission node in the embodiment in Figure 12A and Figure 12C shows a flowchart used when the data is received in -X direction. Detailed Description of the Preferred Embodiment Figure 4 shows a block diagram of a principle of the present invention by explaining a structure of node 10. Receiving process units 11, 12,... 1N, and 21, 22, ...2N are for receiving the data transmitted from the other node in respective directions. A destination detecting unit 13 detects the destination information designating the scope of the destination node from the data. A between-node distance process unit 14 obtains the node distance between the particular computer node and the destination computer node based on the destination information. A destination judgment unit 15 judges whether or not the data should be obtained by the self node and whether or not the data should be transmitted further or relayed based on the node distance information. It then judges the transmission direction. Transmission process units 31, 32, ... 3N, and 41, 42, ... 4N are for transmitting the data subjected to destination judgment. The operation of the apparatus shown in Figure 4 is explained. As shown in Figure 4, the receiving process units 11, 12 ... 1N, and 21, 22,... 2N receive the data transmitted from the other nodes in respective directions. A destination detecting unit 13 detects the destination information designating the scope of the destination node from the data between-node distance processing unit for obtaining a node distance between the particular computer node and the destination computer node based on the destination information. Next, a destination judgment unit 15 judges whether the data should be obtained by the self node and then obtains the data. Simultaneously, the destination judgment unit 15 determines whether or not the distance is 0 based on the obtained between-node distance and then determines the direction in which the data is further transmitted. It then provides the data to the transmission processing units in respective directions. Transmission processing units 31, 32...3N, and 41, 42, 4N transmit the data provided from the destination judgment unit 15 to the destination node. As shown in Figures 5A to 5C, the message is divided into transmission units of flits 51. Header flit 51-1, having the scope information of the broadcast communication, is provided at the head of the message and the end flit 51-2 is provided at the end of the message. The message is sequentially transmitted from one node 10a to the other node 10b in the network. The receiving node 10 refers to header flit 51-1 and when the scope information designates that the message should be transmitted to the other node 10, the scope information is updated and header flit 51-1 is transmitted to the other node 10 in the transmission direction and the following flits 51 transmitted after the header flit 51-1 are sequentially transmitted until the end flit 51-2 is transmitted. Therefore, the scope information of the broadcast communication is provided to header flit 51-1 at the head of the flit 51 obtained by dividing the message into transmission units and then flits 51 are sequentially transmitted. Node 10b, which receives the flit, refers to the scope information, preserves the message in the self node and transmits it to the other node 10 in the transmission direction. This operation is repeated, thereby achieving a high speed and efficient broadcast communication in the worm-hole routing. According to the worm-hole routing in a communication system between parallel computers is provided, the message is divided into the smallest possible transfer unit (comprising several bytes), called a flit, and transmits the header flit with the destination information. The header flit is then transmitted from node to node through a relay route within a network until it reaches the destination node. The flits following the header flit are sequentially transmitted to the destination node by occupying the transmission route until the end flit reaches the destination node, thus enabling one block of the message to be transmitted. Figure 5A shows an example of a data flow of a broadcast communication in a one dimensional network. 10a is a transmission node and the hatched nodes 10b designate the receiving nodes. In this case, the scope information of the transmission is 2 and thus the message is broadcast to the node provided two nodes ahead in both directions from transmission node 10a. Figure 5B shows an example of data of a broadcast communication in a two dimensional network. 10a designates a transmission node and the hatched nodes 10b designate the receiving nodes. In this case, the scope information of the transmission is 2 in the X direction and 1 in the Y direction. The message is broadcast to the node two nodes ahead in the +X and -X directions and is broadcast to the node provided one node ahead in the +Y and -Y directions from transmission node 10a. Figure 5C shows an example of a flit. Flit 1 is obtained by dividing the message into transmission units (for example, units of several bytes). The message comprises a header flit 51-1 provided at the head of the message, flits with data and an end flit 51-2 provided at the end of the message. The scope information of the transmission in the broadcast communication is stored in the header flit 51-1. The scope information of the transmission designates the number of nodes through which the message is transmitted in a one-dimensional network and designates the number of nodes through which the message is transmitted in *X direction and *Y direction in the two-dimensional network. The end flit 51-2 designates EOD (end of file or the end of the flit) by making the end bit "1". The present invention is explained in detail by referring to the flowchart shown in Figure 6. In Figure 6A, at step S1, the header flit is received and preserved. For example, a hatched node 10b, as shown in Figures 5A and 5B, receives header flit 51-1 shown in Figure 5C and preserves the content of the message in the self node 10. At step S2, the scope information of the transmission within the header flit is referred to. Step S3 determines whether the content of the header flit is other than 0. In case of YES, the flits (including the header flit and the other flits) are sequentially transmitted in the transmission direction through steps S4 to S7. In case of NO in step 3, the self node is the end node of the broadcast communication and the header flit is not transmitted to the other node. The following flits, including the end flit, are preserved at step S8. In step S4, 1 is subtracted from the scope information of the transmission. The scope information of the transmission is thereby judged as being other than 0 in step S3 and transmission of the message to the other node is required. In step S5, the flit (including the head flit and data flit) is transmitted in the transmission direction. Therefore, the flit is transmitted to the adjacent node in the transmission direction. In step S6 it is judged whether the transmission of the end flit is completed. In the case of YES, all the flits from the header flit to the end flit are transmitted in the transmission direction, thereby completing the process. In case of NO, the next flit is received in step S7, and it is preserved and transmitted in the transmission direction, as shown in step S5. This routing process is repeated. According to the above recited procedure, in a certain node, 1 is subtracted from the scope information of the transmission when the scope information of the transmission of the received head flit 51-1 is other than 0 and the head flit 51-1 to end flit 51-2 are sequentially transmitted to the node provided in the transmission direction. Therefore, the broadcast communication continues until the scope information becomes 0. As shown in Figure 6B, the process (setp S3) of subtracting 1 from the scope information may be performed prior to the judgment (step S4) as to whether the scope information is 0. Figure 7A shows an example of one node used for the two-dimensional network shown in Figure 5B. 10-1 is a block for performing a routing in the X direction. 10-2 is a block for performing a routing in the Y direction. FIFO is a buffer for temporarily storing the data (flit) flowing from the X direction to the Y direction. The scope information in the X direction within the header flit 51-1 received by block 10-1 has 1 subtracted from it and is transmitted to the adjacent node in the +X direction or to the adjacent node in the -X direction in accordance with the scope information in the X direction. The scope information in the Y direction within the header flit 51-1 received by block 10-2 is transmitted to the adjacent node in the +Y direction or the adjacent node in the -Y direction in accordance with the scope information in the Y direction. Figure 7B shows the whole structure of the present invention in which the example of the node shown in Figure 7A forms the two-dimensional network as shown in Figure 5B. The routing 10-3 forms a routing operation in the *X direction and the *Y direction and a processor 10-4 performs the above recited process to conduct a broadcast communication within a limited scope information. The routing 10-3 and the processor 10-4 operate in accordance with a flowchart shown in Figures 6A or 6B. The operations in the X and Y directions are explained in more detail by referring to Figures 8 to 10. Figure 8 shows a process block diagram of a node 10 according to the present embodiment. Receiving process units 111 and 121 receive the data transmitted in the X direction, and receiving process units 112 and 122 receive data transmitted in the Y direction. Destination detecting unit 113 detects the destination information designating the scope of the destination node from the data. The X-direction between-node distance processing unit 114 and the Y-direction between node distance processing unit 124 obtain the node distance between the particular computer node and the destination computer node based on the destination information. The X-direction destination judgment unit 115 and the Y-direction destination judgment unit 125 judge whether or not the data should be obtained by the self node and judges based on the distance information whether or not further transmission of data is necessary and determines the transmission direction. The X direction transmission process unit 131 and 141 and Y direction transmission process unit 132 and 142 for transmitting the data whose destination is determined. Data transmission request unit 108 determines the scope of the broadcast communication and requests the broadcast communication in accordance with an input designation from a keyboard, for example, as a means for requesting the transmission, where particular node is the transmission source node. Next, the operation of the present embodiment is explained where the transmission node N31 performs a broadcast communication toward respective receiving nodes in a two-dimensional lattice network as shown in Figure 9. Where the broadcast communication starts from transmission node N31, firstly, the scope of the communication is designated. Then, as shown in the transmission node process flow shown in Figure 10A, data process request unit 108 produces the data designating that the broadcast scope of the X direction = 2 and that the broadcast scope of the Y direction = 1, at step S11. At step S12, the distance in the X direction is determined based on the request data. When the distance in the X direction is not 0, at the next step S13, the data is transmitted in both the +X and the -X directions. The data is also transmitted in the +Y and the -Y directions through the processes recited in steps S14 and S15. Figures 10B to 10E show the process flow in respective nodes of the data transmission from transmission node N31 to receiving node N34. Transmission node N31 transmits the data with the scope of the node designated as 2 in the X direction and 1 in the Y direction. The receiving node N32 receives the data from node N31 in the -X direction at step S21. Next, destination detecting unit 103 detects destination information XID and YID. As XID=2 at first, between-node distance XID is obtained at step S22 by subtracting 1 from the destination information XID. Then the new XID=XID-1=1. Thus, step S23 judges weather XID=0 in order to determine that the data should be further transmitted in the X direction. The following step S24 then transmits data in the +Y direction. On the other hand, as Y direction between-node distance YID=1, step S25 determines that the data should be transmitted in the Y direction, and at step S26, data is transmitted in the +Y and the -Y directions. Next, the process flow of node N33 receiving the data from receiving node N32 also performs as shown in Figure 10B. Namely, if the process flow is for receiving the data in the -X direction (step S2), XID=1 at first, and the new XID=XID-1=0 (step S23). Thus, the data transmission is not performed in the X direction (step S24). On the other hand, Y-direction between-node distance YID=1 and the data is transmitted in the +Y and -Y directions (steps S25 and S26). The step S21 corresponds to -X direction receiving process unit 11 and destination detection unit 13 shown in Figure 4, the step S22 between-node distance process unit 14, the step S23 destination judgement unit 15, and the step S24 +X direction transmission process unit 31. The process of the node N34 receiving the data from node N33 is shown in Figure 10D. At first, at step S41, the data is received in the -Y direction and as YID=1 at first, the new YID=YID-1 of the between-node distance is obtained at step S42 and step S43 determines that the data is not transmitted in the Y direction when YID=0 (step S43). Then, the step for transmitting data in the +Y direction (step S44) is not performed. Figure 10C and Figure 10E show respectively the process for receiving the data from a right node in the +X direction in accordance with steps S31 to S36 and the process for receiving data from an upper node in the +Y direction in accordance with steps S51 to S54. A similar process in accordance with the flowchart in Figures 10A to 10E is conducted in other receiving nodes and thus the data is transmitted to the nodes provided within the designated scope and the data is broadcast to all the nodes within the designated scope. The system according to the present invention can be applied not only to a broadcast communication in which the scope of the symmetry area is designated with the transmission node as the center, but also to a broadcast communication in which the scope of the communication is shifted in a particular direction as shown in Figure 11A by providing a different value of X between the plus direction and the minus direction. Figure 11B shows a flowchart designating a control of a broadcast communication in which a broadcast scope is designated in a manner that it is shifted in a particular direction as shown in Figure 11A. X direction between-node distance is defined as between-node distance in +X direction XID+ and between-node distance in -X direction XID-. XID+ is not equal to XID-. The header of the message include these two, namely, XID+ and XID-. Figure 11B shows a flowchart performed for a transmission node. When data transmission is requested, it is judged whether or not XID+ = 0. If XID+ is not equal to 0, the data is transmitted in the +X direction. When XID+ = 0, data is not transmitted in the +X direction and it is judged whether XID- = 0. If XID- is not equal 0, the data is transmitted in the -X direction. When data XID+ is received in the -X direction, data is processed in accordance with a flowchart shown in Figure 10B. When the data XID- is received the data is transmitted as shown in Figure 10C. In an example shown in Figure 11A, XID+=2 and XID-=1. At the transmission node, data are respectively transmitted in the +X direction and -X direction as XID+=2 and is not equal to 0 and XID-=1, and is not equal to 0. The receiving node in the +X direction, XID+=2 is subtracted by 1 at the node in accordance with the flowchart shown in Figure 10B and the data is transmitted to the second node counting from the transmission node in the +X direction. The receiving node in the -X direction provides XID+ -1=1 in accordance with the flowchart shown in Figure 10C and thus the data is transmitted to the first node in the -X direction. Therefore, a shifted scope of the node with regard to the transmission node can be designated as the broadcast scope. The designation of the scope is also made possible in one direction by providing two values X1 and X2, in the same direction, for example, in X direction making it possible to designate the scope of the communication without including the transmission node, as shown in Figure 12A. Figures 12B and 12C show a flowchart designating a control of a broadcast communication to designate the scope of the broadcast which does not include the transmission node, as shown in Figure 12A. The between-node distance in the X direction is XID1 and XID2. XID1<XID2 and both XID1 and XID2 are not negative. Figure 12B shows a flowchart for the transmission node. When the data transmission is requested, when XID1 is not equal to 0 and XID2 is not equal to 0, data is transmitted in the +X direction. When XID1=0 and XID2=0, data is not transmitted from the transmitting node. Next, as shown in Figure 12C, according to the flowchart for a receiving node for receiving the data in the -X direction it is judged whether XID1=0. When XID1 is not equal to 0, the operations of XID1=XID1-1 and XID2=XID2-1 are performed and the data is transmitted in the +X direction. When XID=0, it is judged whether XID2=0. When XID2 is not equal 0, an operation of XID2=XID2-1 is performed and the data is further transmitted in the +X direction. Then the process advances to the process in the Y direction. In the next node, when XID1=0, it is judged whether XID2=0. If XID2=0, the data is no longer transmitted in the +X direction and the process starts for the Y direction. In the example shown in Figure 12A, XID1=2 and XID2=4, as a transmission node, XID1=2 and is not equal to 0 and XID2=4 and is not equal to 0, data is transmitted in the +X direction, as shown in Figure 12B. The first node on the right side from the transmission node, XID1=2-1=1 and XID2=4-1=3 and thus data is transmitted in the +X direction. In the second node on the right side from the transmission node, XID1=2-1-1=0 and XID2=4-1-1=2 and thus data is further transmitted in the +X direction. In the third node on the right from the transmission node, XID1=0 and XID2=XID2-1 =4-2-1=1 the data is further transmitted in the +X direction. At the fourth node on the right from the transmission node, XID2=4-2-1-1=0 and thus data is not transmitted in the +X direction and the process for the Y direction will start. In a one-dimensional connection, only the X direction can be considered. In a three dimensional connection, the process in the Z direction may be added to those in the X and Y directions. In an N-dimensional connection, processes may be added in accordance with the number of dimensions. On the other hand, for the apparatus of the transmission source node for performing a transmission request, the scope of the broadcast communication is designated and transmitted to the data transmission request part 108, thereby forming the data designating the scope of the broadcast communication and transmitting the data to the destination judgment unit 115, in accordance with the block diagram shown in Figure 8. As described above, according to the present invention, in a communication between parallel computers connected in a torus connection or a matrix connection, the message is divided into a flit 51 of the transfer unit, sequentially transferred by providing the header flit 51-1 with the scope information of the transmission and referred to the scope information in the receiving node 10b to preserve the received data in the self node. The received data is then simultaneously transmitted to the adjacent node in the transmission direction. This operation is repeated, so that the broadcast communication to the node with the designated scope can be performed with a smaller number of data transmissions and the designation of the scope of the communication can be easily made. This facilitates a communication node at each node and increases the efficiency of the communication control.

Claims: A communication control system between parallel computers for performing a broadcast communication in a network between parallel nodes (10), in which each of said nodes (10) comprises: data receiving means (11,12,...1N; 21,22,...2N) for receiving the data transmitted from other nodes in respective directions; destination detecting means (13) for detecting destination information from the data; between-node distance processing means (14) for obtaining distance information between a particular computer node and the destination node, based on the destination information; destination judgement means (15) for judging whether the data should be obtained by a local node, for judging, whether the data should be further transmitted to another node and for determining a direction of the transmission, based on the distance information; and transmitting process means (31,32,...3N; 41,42,...4N) for transmitting the data whose destination is judged, with regard to a particular direction; characterised in that: said destination information designates a scope of destination nodes for the data, and in that said transmitting process means are arranged to transmit the data to all other nodes within said scope. The communication control system according to claim 1, wherein said scope of the destination nodes is determined as a symmetric area with an originating node as the center of said symmetric area. The communication control system according to claim 1, wherein the scope of the destination nodes is shifted in one direction with respect to a symmetric scope of the destination nodes with the originating node as the center. The communication control system according to claim 1, wherein said scope of the destination nodes is determined without providing an originating node within the scope of the destination node. The communication control system according to claim 1, wherein said parallel nodes (10) comprise computers connected in an N-dimension torus connection or N-dimension matrix connection. The communication control system according to claim 1, further comprising means for dividing said data into a plurality of flits constituting transmission units of said communication including: a head flit at the head of said data, containing said destination information designating a scope of destination nodes and an end flit at the end of said data; and wherein, in each said node (10), in response to reception of said head flit by said data receiving means, said destination detecting means (13), between-node distance processing node (14), destination judging means (15) and transmitting process means update the scope of the transmission, and transmit the header flit to another node provided in the transmission direction, when the scope information in said header flit designates that the message should be transmitted to other nodes, thereby sequentially transmitting the flits following the header flit until the end flit is transmitted.

Inventors: HORIE TAKESHI, HORIE, TAKESHI
Applicants: FUJITSU LTD, FUJITSU LIMITED
Application year: 1990
Main classification: G06F15
IPC codes: G06F15