[MPICH2-dev] problem with multithreaded version of MPI_Comm_split() in mpich2-1.03

[Ryzhykh, Alexey]

Hi,

I am working at Intel Parallel System & Applications group

I used mpich2-1.03 with sock device to run some MPI multithreaded
application.

Mpich2-10.3 was built to support MPI_THREAD_MULTIPLE level.

The application creates the communicator for each thread by means of
MPI_Comm_split() function.

This communicator is needed in order to MPI messages on one thread don't
intersect with messages on other thread.

But sometimes I see that the field context_id  is the same for different
thread communicators.

I created the test (see enclosed file test.tgz) to demonstrate the
problem. But this test  uses internal mpich2-1.03  definitions to check
the value of context_id.

Sometimes it fails as below:

nthreads=32

nthreads=32

[0] context_id=184 i=6 j=12

[1] context_id=184 i=6 j=12

 test failed, number of errors is 1

 test failed, number of errors is 1

The failure shows that context_id is the same for different
communicators.

 

I have prepared the simple fix of this bug. See in attachment enclosed
file commutil.c.diff

I believe that the bug is be fixed  after applying this patch to the
source file  mpich2-1.0.3/src/mpi/comm/commutil.c

 

With best regards,

Alexey Ryzhykh,

---

Intel, Sarov

 

 

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