Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] MPI_Send doesn't work if the data >= 2GB
From: ÃÏÏܾü (xjun.meng_at_[hidden])
Date: 2010-12-07 22:29:55


Hi Bowen,

Thanks very much. I had checked my writev system call, I thought it was him
that caused all these bad things :)

Best Regards
Xianjun Meng

2010/12/8 Bowen Zhou <bwzhou_at_[hidden]>

> On 12/05/2010 10:13 PM,
>
>> hi,
>>
>> I met a question recently when I tested the MPI_send and MPI_Recv
>> functions. When I run the following codes, the processes hanged and I
>> found there was not data transmission in my network at all.
>>
>> BTW: I finished this test on two X86-64 computers with 16GB memory and
>> installed Linux.
>>
>> 1 #include <stdio.h>
>> 2 #include <mpi.h>
>> 3 #include <stdlib.h>
>> 4 #include <unistd.h>
>> 5
>> 6
>> 7 int main(int argc, char** argv)
>> 8 {
>> 9 int localID;
>> 10 int numOfPros;
>> 11 size_t Gsize = (size_t)2 * 1024 * 1024 * 1024;
>> 12
>> 13 char* g = (char*)malloc(Gsize);
>> 14
>> 15 MPI_Init(&argc, &argv);
>> 16 MPI_Comm_size(MPI_COMM_WORLD, &numOfPros);
>> 17 MPI_Comm_rank(MPI_COMM_WORLD, &localID);
>> 18
>> 19 MPI_Datatype MPI_Type_lkchar;
>> 20 MPI_Type_contiguous(2048, MPI_BYTE, &MPI_Type_lkchar);
>> 21 MPI_Type_commit(&MPI_Type_lkchar);
>> 22
>> 23 if (localID == 0)
>> 24 {
>> 25 MPI_Send(g, 1024*1024, MPI_Type_lkchar, 1, 1, MPI_COMM_WORLD);
>> 26 }
>> 27
>> 28 if (localID != 0)
>> 29 {
>> 30 MPI_Status status;
>> 31 MPI_Recv(g, 1024*1024, MPI_Type_lkchar, 0, 1, \
>> 32 MPI_COMM_WORLD, &status);
>> 33 }
>> 34
>> 35 MPI_Finalize();
>> 36
>> 37 return 0;
>> 38 }
>>
>> Thanks
>> Xianjun
>>
>>
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
> Hi,
>
> It might be a problem with the Linux TCP stack. The similar issue happens
> with MPICH2 too. Can you try with message size (2G-1) bytes?
> http://trac.mcs.anl.gov/projects/mpich2/ticket/1080
>
> Best,
> Bowen Zhou
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users
>