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Subject: Re: [OMPI users] MPI_Send doesn't work if the data >= 2GB
From: ÃÏÏܾü (xjun.meng_at_[hidden])
Date: 2010-12-05 23:17:43


hi,

In my computers(X86-64), the sizeof(int)=4, but the
sizeof(long)=sizeof(double)=sizeof(size_t)=8. when I checked my mpi.h file,
I found that the definition about the sizeof(int) is correct. meanwhile, I
think the mpi.h file was generated according to my compute environment when
I compiled the Openmpi. So, my codes still don't work. :(

Further, I found when I called the collective routines(such as,
MPI_Allgatherv(...)) which are implemented by the Point 2 Point don't work
either when the data > 2GB.

Thanks
Xianjun

2010/12/6 Tim Prince <n8tm_at_[hidden]>

> On 12/5/2010 7:13 PM, ÃÏÏܾü wrote:
>
>> 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 }
>>
>> You supplied all your constants as 32-bit signed data, so, even if the
> count for MPI_Send() and MPI_Recv() were a larger data type, you would see
> this limit. Did you look at your <mpi.h> ?
>
> --
> Tim Prince
>
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