mpi

问题 Say, i have 8 processes. When i do the following, the MPU_COMM_WORLD communicator will be splitted into two communicators. The processes with even ids will belong to one communicator and the processes with odd ids will belong to another communicator. color=myid % 2; MPI_Comm_split(MPI_COMM_WORLD,color,myid,&NEW_COMM); MPI_Comm_rank( NEW_COMM, &new_id); My question is where is the handle for these two communicators. After the split the ids of processors which before were 0 1 2 3 4 5 6 7 will

问题 I have this array [1 2 3 4 5 6 7 8 9] and i am performing scan operation on that. I have 3 mpi tasks and each task gets 3 elements then each task calculates its scan and returns result to master task task 0 - [1 2 3] => [1 3 6] task 1 - [4 5 6 ] => [4 9 15] task 2 - [7 8 9] => [7 15 24] Now task 0 gets all the results [1 3 6] [4 9 15] [7 15 24] How can I combine these results to produce final scan output? final scan output of array would be [1 3 6 10 15 21 28 36 45] can anyone help me please?

问题 I have to send and receive (MPI) a chunk of a multi-dimensional array in FORTRAN 90. The line MPI_Send(x(2:5,6:8,1),12,MPI_Real,....) is not supposed to be used, as per the book "Using MPI..." by Gropp, Lusk, and Skjellum. What is the best way to do this? Do I have to create a temporary array and send it or use MPI_Type_Create_Subarray or something like that? 回答1: The reason not to use array sections with MPI_SEND is that the compiler has to create a temporary copy with some MPI

问题 Is MPI_Bsend good when I want to free resources exactly after async Send? Will this : MPI_Bsend(&array[0],...) delete[] array; prevent me from deleting memory that I want to send ( the problem is, when appropriate recv will be on, the array may be already deleted)? UPD: void RectMPIAngleFiller::setglobalFillerbounds1() { int_t SIZE = getSolver()->getNumInterpolators() * procnums; int_t gridnums = getSolver()->getNumGrids(); if (layer == 1) { if (local_rank == 0) { MPI_Isend(&rank_size, 1, MPI

问题 I have a number of 2d arrays of size = (2,9) on different processes, which I want to concatenate using MPI_Gatherv in a global array of size = (2*nProcs,9) on the root process. For this I'm trying to adapt this post: Sending 2D arrays in Fortran with MPI_Gather But I do really understand what they are doing and my example isn't working: program testing use mpi implicit none integer(4), allocatable :: local(:,:) integer(4), allocatable :: global(:,:), displs(:), counts(:) integer(4) :: me,

问题 After have been investigating my problem for weeks I have found some information from the hexdump of the context(I got one without C/R error (links at the end of this question, but no restart success)) (context-num0-0-0, DropBox) <<cut>> cri_sig_handle.Failed to reregister signal %d in process %d. Saw %p when expecting %p (%s) or %p (cri_sig_handler)....cri_run_sig_handler. Failed to allocate signal %d in process %d: got signal %d instead...sigfillset() failed: %s.sigaction() failed: %s.

问题 After have been investigating my problem for weeks I have found some information from the hexdump of the context(I got one without C/R error (links at the end of this question, but no restart success)) (context-num0-0-0, DropBox) <<cut>> cri_sig_handle.Failed to reregister signal %d in process %d. Saw %p when expecting %p (%s) or %p (cri_sig_handler)....cri_run_sig_handler. Failed to allocate signal %d in process %d: got signal %d instead...sigfillset() failed: %s.sigaction() failed: %s.

问题 Recently working in parallel domain i come to know that there are two terms "vertical parallelism " and "horizontal parallelism". Some people says openmp ( shared memory parallelism ) as vertical while mpi ( distributed memory parallelism ) as horizontal parallelism. Why these terms are called so ? I am not getting the reason. Is it just terminology to call them so ? 回答1: The terms don't seem to be widely used, perhaps because often time a process or system is using both without distinction.

问题 Why these lines of code: if(my_rank != 0) { sprintf(msg, "Hello from %d of %d...", my_rank, comm_sz); if(my_rank == 2) { sleep(2); sprintf(msg, "Hello from %d of %d, I have slept 2 seconds...", my_rank, comm_sz); } MPI_Send(msg, strlen(msg), MPI_CHAR, 0, 0, MPI_COMM_WORLD); } else { printf("Hello from the chosen Master %d\n", my_rank); for(i = 1; i < comm_sz; i++) { MPI_Recv(msg, MAX_STRING, MPI_CHAR, i, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE); printf("%s\n", msg); } } give this result? Hello

问题 I am inverting a matrix via a Cholesky factorization, in a distributed environment, as it was discussed here. My code works fine, but in order to test that my distributed project produces correct results, I had to compare it with the serial version. The results are not exactly the same! For example, the last five cells of the result matrix are: serial gives: -250207683.634793 -1353198687.861288 2816966067.598196 -144344843844.616425 323890119928.788757 distributed gives: -250207683.634692