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Subject: Re: [OMPI users] MPI_Send doesn't work if the data >= 2GB
From: ÃÏÏܾü (xjun.meng_at_[hidden])
Date: 2010-12-06 22:19:05


Hi

Are you running on two processes (mpiexec -n 2)?
Yes

Have you tried to print Gsize?
Yes, I had checked my codes several times, and I thought the errors came
from the OpenMpi. :)

The command line I used:
"mpirun -hostfile ./Serverlist -np 2 ./test". The "Serverlist" file include
several computers in my network.

The command line that I used to build the openmpi-1.4.1:
./configure --enable-debug --prefix=/usr/work/openmpi ; make all install;

What interconnect do you use?
It is normal TCP/IP interconnect with 1GB network card. when I debugged my
codes(and the openmpi codes), I found the openMpi do call the
"mca_pml_ob1_send_request_start_rdma(...)" function, but I was not quite
sure which protocal was used when transfer 2BG data. Do you have any
opinions? Thanks

Best Regards
Xianjun Meng

2010/12/7 Gus Correa <gus_at_[hidden]>

> Hi Xianjun
>
> Are you running on two processes (mpiexec -n 2)?
> I think this code will deadlock for more than two processes.
> The MPI_Recv won't have a matching send for rank>1.
>
> Also, this is C, not MPI,
> but you may be wrapping into the negative numbers.
> Have you tried to print Gsize?
> It is probably -2147483648 in 32bit and 64bit machines.
>
> My two cents.
> Gus Correa
>
> Mike Dubman wrote:
>
>> Hi,
>> What interconnect and command line do you use? For InfiniBand openib
>> component there is a known issue with large transfers (2GB)
>>
>> https://svn.open-mpi.org/trac/ompi/ticket/2623
>>
>> try disabling memory pinning:
>> http://www.open-mpi.org/faq/?category=openfabrics#large-message-leave-pinned
>>
>>
>> regards
>> M
>>
>>
>> 2010/12/6 <xjun.meng_at_[hidden] <mailto:xjun.meng_at_[hidden]>>
>>
>>
>> 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] <mailto:n8tm_at_[hidden]>>
>>
>>
>> On 12/5/2010 7:13 PM, Xianjun 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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