I run several times of the program, the results are as the same as before. Could you tell me your MPICH version and compiling parameters? The version of my MPICH is 3.1.3, I compile it as

$ mpirun --version

HYDRA build details:

Version: 3.1.3

Release Date: Wed Oct 8 09:37:19 CDT 2014

CC: gcc -fPIC

CXX: g++

F77: gfortran

F90: gfortran

Configure options: '--disable-option-checking' '--prefix=/usr/local/mpich3' '--with-device=ch3:nemesis' 'CFLAGS=-fPIC -O2' '--disable-fortran' '--cache-file=/dev/null' '--srcdir=.' 'CC=gcc' 'LDFLAGS= ' 'LIBS=-lpthread ' 'CPPFLAGS= -I/home/valder/Downloads/Software/mpi/mpich-3.1.3/src/mpl/include -I/home/valder/Downloads/Software/mpi/mpich-3.1.3/src/mpl/include -I/home/valder/Downloads/Software/mpi/mpich-3.1.3/src/openpa/src -I/home/valder/Downloads/Software/mpi/mpich-3.1.3/src/openpa/src -D_REENTRANT -I/home/valder/Downloads/Software/mpi/mpich-3.1.3/src/mpi/romio/include'

Process Manager: pmi

Launchers available: ssh rsh fork slurm ll lsf sge manual persist

Topology libraries available: hwloc

Resource management kernels available: user slurm ll lsf sge pbs cobalt

Checkpointing libraries available:

Demux engines available: poll select

the whole program is

=========

#include "mpi.h"

#include <stdio.h>

#include <stdlib.h>

#include <sys/time.h>

typedef unsigned char byte;

int main(int argc, char *argv[]){

int rank,size;

byte buf[10][10];

MPI_Request req[10];

MPI_Status stat[10];

int outcount;

int array_of_indices[10];

int i;

int complete = 0;

MPI_Init(&argc, &argv);

MPI_Comm_size(MPI_COMM_WORLD, &size);

MPI_Comm_rank(MPI_COMM_WORLD, &rank);

if(rank==0) {

for(i =0; i< 10;i++){

MPI_Isend(buf[i], 10, MPI_BYTE, 1, 123, MPI_COMM_WORLD, &req[i]);

}

printf("post send\n");

}else {

for(i=0; i< 10;i++){

MPI_Irecv(buf[i], 10, MPI_BYTE, 0, 123, MPI_COMM_WORLD, &req[i]);

}

printf("post recv\n");

}

for (;;){

MPI_Waitsome(10, req, &outcount, array_of_indices, stat);

complete += outcount;

printf("rank %d %d index %d\n", rank, outcount, array_of_indices[0]);

if(complete == 10)

break;

}

printf("rank %d complete\n", rank);

MPI_Finalize();

}

=========

I compile it as

$ mpicc -o tests testsome.c

and run as

$ mpirun -n 2 ./tests

At 2014-10-20 09:02:39, "Junchao Zhang" <jczhang@mcs.anl.gov> wrote:

I think it is random. For example, I ran your code and its output was:
post recv
post send
rank 0 10 index 0
rank 0 complete
rank 1 1 index 0
rank 1 9 index 1
rank 1 complete

--Junchao Zhang

On Sun, Oct 19, 2014 at 9:48 AM, myself <chcdlf@126.com> wrote:
Because I want to understand the behavior of MPI_Waitsome, I change the program as fellow. MPI can waitsome 10 Isend request once time, while waitsome 1 Irecv request each time. Why waitsome-Irecv can not be more than 1 as I expect?
=====
MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &size);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);

if(rank==0) {
for(i =0; i< 10;i++){
MPI_Isend(buf[i], 10, MPI_BYTE, 1, 123, MPI_COMM_WORLD, &req[i]);
}
printf("post send\n");
}else {
for(i=0; i< 10;i++){
MPI_Irecv(buf[i], 10, MPI_BYTE, 0, 123, MPI_COMM_WORLD, &req[i]);
}
printf("post recv\n");
}

for (;;){
MPI_Waitsome(10, req, &outcount, array_of_indices, stat);
complete += outcount;
printf("rank %d %d index %d\n", rank, outcount, array_of_indices[0]);
if(complete == 10)
break;
}
printf("rank %d complete\n", rank);
MPI_Finalize();
=====
$ mpirun -n 2 ./tests
post send
post recv
rank 0 10 index 0
rank 0 complete
rank 1 1 index 0
rank 1 1 index 1
rank 1 1 index 2
rank 1 1 index 3
rank 1 1 index 4
rank 1 1 index 5
rank 1 1 index 6
rank 1 1 index 7
rank 1 1 index 8
rank 1 1 index 9
rank 1 complete

At 2014-10-19 22:36:25, "Bland, Wesley B." <wbland@anl.gov> wrote:

You need to move your waitany outside of the if statement so both ranks execute it.

On Oct 19, 2014, at 9:33 AM, myself <chcdlf@126.com> wrote:

Here is my test program

======

#include "mpi.h"

#include <stdio.h>

#include <stdlib.h>

#include <sys/time.h>

typedef unsigned char byte;

int main(int argc, char *argv[]){

MPI_Init(&argc, &argv);

int rank,size;

MPI_Comm_size(MPI_COMM_WORLD, &size);

MPI_Comm_rank(MPI_COMM_WORLD, &rank);

byte buf[10][10];

MPI_Request req[10];

MPI_Status stat[10];

int outcount;

int array_of_indices[10];

int i;

if(rank==0) {

for(i =0; i< 10;i++){

MPI_Isend(buf[i], 10, MPI_BYTE, 1, 123, MPI_COMM_WORLD, &req[i]);

}

printf("post send\n");

MPI_Waitall(10, req, stat);

printf("send over\n");

}else {

for(i=0; i< 10;i++){

MPI_Irecv(buf[i], 10, MPI_BYTE, 0, 123, MPI_COMM_WORLD, &req[i]);

}

printf("post recv\n");

for (i=0;i<10;i++){

MPI_Waitsome(10, req, &outcount, array_of_indices, stat);

printf("%d index %d\n", outcount, array_of_indices[0]);

}

}

MPI_Finalize();

}

======

get the result like this

======

$ mpirun -n 2 ./tests

post send

send over

post recv

1 index 0

1 index 1

1 index 2

1 index 3

1 index 4

1 index 5

1 index 6

1 index 7

1 index 8

1 index 9

======

I think I should get some completed receive connection, not just 1.

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