1 / 23

MPI One-Sided and Two-Sided Communication

MPI One Sided and Two-Sided Communication: Table of Contents. MPI CommunicationIntroduction to MPI CommunicationExample of MPI CommunicationMPI Two-Sided Communication Definition of MPI Two-Sided CommunicationExample of MPI Two-Sided CommunicationDiagram of MPI Two-Sided CommunicationMPI One-

stacy
Télécharger la présentation

MPI One-Sided and Two-Sided Communication

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. MPI One-Sided and Two-Sided Communication Computer Science Colloquium Akinwunmi (Akin) Odeniyi Advisor: Dr. Kai Wang, PhD.

    2. MPI One Sided and Two-Sided Communication: Table of Contents MPI Communication Introduction to MPI Communication Example of MPI Communication MPI Two-Sided Communication Definition of MPI Two-Sided Communication Example of MPI Two-Sided Communication Diagram of MPI Two-Sided Communication MPI One-Sided Communication. Definition of MPI One-Sided Communication Example of MPI One-Sided Communication Diagrams of MPI One-Sided Communication 5/18/2012 2

    3. MPI One Sided and Two-Sided Communication: Table of Contents Transposing an n by n matrix using two processors Program code using Two-Sided Communication Program code using One-Side Communication Performance study of MPI communication models Tabulation of data Graphs of findings Analysis of results Conclusion. Review. Sources. Thanks 5/18/2012 3

    4. MPI Communication: Introduction MPI (Message Passing Interface) is a Library specification for message passing. Standard for writing message-passing programs. It allows many computers to communicate . There are two types of MPI Communication MPI Two-Sided Communication Model MPI Standard 1 (MPI-1). MPI One-Sided Communication Model MPI Standard 2 (MPI-2). 5/18/2012 4

    5. MPI Communication: Why is Communication Needed? Assume we want to add numbers 1 to 100. Let a processor perform an addition in 1 second. This processor will sum all numbers in 99 seconds. Two processors can reduce computation time. Each processor will sum numbers in 49 seconds. It requires 1 second to add the two final results. Processors need to communicate in order to: Distribute the numbers 1 to 100 evenly. Determine the sum of their computation results. Communication is needed in MPI for effective programming. 5/18/2012 5

    6. Two-Sided Communication in MPI-1: Definition Two-Sided Communication Evident in the use of most MPI function calls. Parameters is specified by sender and receiver. Data moves between processes address spaces. Senders Side: MPI_Send() function is called. Receivers Side: MPI_Recv() function is used. Implies some degree of synchronization Receive cant complete until send has started. 5/18/2012 6

    7. MPI Two-Sided Communication: Example The sum of 1 to 100 described above can be done with Two-Sided communication model. Processor 1 Sends the numbers {1, 3, , 99} to processor 2. Receives the sum of {1, 3, , 99} from processor 2. Processor 2 Receives sequence {1, 3, , 99} from processor 1. Sends the series: 1 + 3 + + 99 to processor 1. 5/18/2012 7

    8. Two-Sided Communication: Diagram 5/18/2012 8

    9. One-Sided Communication in MPI-2: Definition Remote Memory Access (RMA) One process specifies communication parameters. Separates communication and synchronization. User imposes right ordering of memory accesses. Origin: the process that performs the call. Target: the process in which memory is accessed. Communication calls MPI_Get: Remote read. MPI_Put: Remote write. 5/18/2012 9

    10. MPI One-Sided Communication: Example. Given a sequence {1, , n} and 2 processors. Processor 1 Loops through {1, , n}. It Informs processor 2 each time it finds a prime. Does not know when next prime will be found. Uses MPI_Put to notify processor 2 of primes. Processor 2 need not loop through {1, , n}. It Does not know how many primes will be found. Remains idle till processor 1 finds or sends prime. 5/18/2012 10

    11. One-Sided Communication: MPI_Get 5/18/2012 11

    12. One-Sided Communication: MPI_Put 5/18/2012 12

    13. One -Sided and Two-Sided Communication: Transposing a Matrix Transposing an n x n matrix named M. For all integer i in [1, n] For all integer j in [1, n] Mji = Mij Programs were written in c language. Programs ran on 2 processors in the rio machine. matTran2.c used MPI_Send and MPI_Recv. matTran1.c used the MPI_Get function. Duration of transposition is given in seconds. 5/18/2012 13

    14. Transposing a Matrix with Two-Sided Communication: matTran2.c t1 = MPI_Wtime(); for(i=0; i<numRows; i++){ for(j=0; j<numCols; j++){ if(myid==0){ matrixVal = matrixArray[k]; k++; MPI_Send(&matrixVal, 1, MPI_INT, 1, tag, MPI_COMM_WORLD); } if(myid==1) { MPI_Recv(&matrixVal, 1, MPI_INT, 0, tag, MPI_COMM_WORLD, &status); matrixArray[(numRows*j)+i] = matrixVal; } } } t2 = MPI_Wtime(); 5/18/2012 14

    15. Transposing a Matrix with One-Sided Communication: matTran1.c if(myid==0){ t1 = MPI_Wtime(); t2 = MPI_Wtime(); t3 = t2-t1; } t1 = MPI_Wtime(); if(myid==0) MPI_Win_create(&matrixVal, sizeof(int), sizeof(int),MPI_INFO_NULL, MPI_COMM_WORLD, &win); else MPI_Win_create(NULL, 0, 1, MPI_INFO_NULL, MPI_COMM_WORLD, &win); for(i=0; i<numRows; i++) { for(j=0; j<numCols; j++) { 5/18/2012 15

    16. Transposing a Matrix with One-Sided Communication: matTran1.c if(myid==0){ matrixVal = matrixArray[k]; k++; MPI_Win_fence(0, win); MPI_Win_fence(0, win);} if(myid==1) { MPI_Win_fence(0, win); MPI_Get(&matrixVal, 1, MPI_INT, 0, 0, 1, MPI_INT, win); MPI_Win_fence(0, win); matrixArray[(numRows*j)+i] = matrixVal;} } } //ends for loops MPI_Win_free(&win); t2 = MPI_Wtime(); duration = t2-t1-t3; 5/18/2012 16

    17. Performance of One-Sided and Two-Sided Communication: Table 5/18/2012 17

    18. Performance of One-Sided and Two-Sided Communication: Graph 1 5/18/2012 18

    19. Performance of One-Sided and Two-Sided Communication: Graph 2 5/18/2012 19

    20. Performance of One-Sided and Two-Sided Communication: Analysis MPI 2-Sided functions transposed the n by n matrix in lesser time for all n observed. Time measured for MPI_Get 1-Sided function increased at a faster rate as n increased. matTran2 halted for n >= 512 with an out of resources error, but matTran1 ran for n > 512. Elapsed time for n = 1 was greater than that for n = 2 in both communication models. 5/18/2012 20

    21. MPI One-Sided and Two-Sided Communication: Summary For efficiency purposes, MPI Two-Sided communication model is better and faster. Every Two-Sided communication problem can be solved with One-Sided communication. Moreover, some problems cannot be solved by MPI Two-Sided communication model. Only MPI One-Sided model will work for the prime number example mentioned earlier. 5/18/2012 21

    22. MPI One-Sided and Two-Sided Communication: Future MPI_Probe() in MPI Standard 1: Solves One-Sided Communication problems. Allows incoming message to be checked for. Does not receive incoming messages. Future research: Comparing performance of the two models. Solving a one sided communication problem. Using MPI_Send, MPI_Recv, and MPI_Probe. Using MPI_Get and or MPI_Put. 5/18/2012 22

    23. MPI One-Sided and Two-Sided Communication: Sources MPICH Home Page: http://www.mcs.anl.gov/research/projects/mpi/mpich1/ MPICH2: High-performance and widely portable MPI http://www.mcs.anl.gov/research/projects/mpich2/ High Performance Computing Class Notes: http://www.usd.edu/~Kai.Wang/Teach.html 5/18/2012 23

    24. MPI One-Sided and Two-Sided Communication: Appreciation Thanks to computer science faculty and staff. Thank you for your time and attention. Gratitude goes to friends and family. Glory be to God! Questions? 5/18/2012 24

More Related