[mpich-discuss] Value of MPI_TAG_UB

[Bibrak Qamar]

I am trying to get the value of MPI_TAG_UB using the following code:

  MPI_Aint  * maxTag;;
  int error, flag;

  error = MPI_Comm_get_attr(MPI_COMM_WORLD, MPI_TAG_UB, &maxTag, &flag);

  if(error != MPI_SUCCESS || !flag ){
  printf( " ERROR IN native mpitagub\n");
  }

  printf( "mpitagub = %d\n", *maxTag);


For MPICH3 I get

mpitagub = 1073741823

I also did it for OpenMPI and I get

mpitagub = 2147483647

The value from OpenMPI makes sense since its 2^31 -1. But at the end the
MPI_TAG_UB is MPI implementation dependent.

*So I was wondering the value that I got from MPICH3 (mpitagub =
1073741823) is this OK? or my code is wrong somewhere?*

Thanks
Bibrak
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