# MPI_Comm_set_info

Set new values for the hints of the communicator associated with comm

## Synopsis

    int MPI_Comm_set_info(MPI_Comm comm, MPI_Info info)

## Input Parameters

comm
  communicator (handle)
info
  info object (handle)

## Notes

The call is collective on the group of comm. The info object may be different on each process, but any info entries that an implementation requires to be the same on all processes must appear with the same value in each process `info object.

## Info hints

mpi_assert_no_any_tag
  boolean, default = false. If set to true, user promises that MPI_ANY_TAG will not be used with the communicator. This potentially allows MPICH to treat messages with different tags independent and seek to improve performance, e.g. by employ multiple network context.

mpi_assert_no_any_source
  boolean, default = false. If set to true, user promises that MPI_ANY_SOURCE will not be used with the communicator. This potentially allows MPICH to treat messages send to different ranks or receive from different ranks independent and seek to improve performance, e.g. by employ multiple network context.

mpi_assert_exact_length
  boolean, default = false. If set to true, user promises that the lengths of messages received by the process will always equal to the size of the corresponding receive buffers.

mpi_assert_allow_overtaking
  boolean, default = false. If set to true, user asserts that send operations are not required to be matched at the receiver in the order in which the send operations were performed by the sender, and receive operations are not required to be matched in the order in which they were performed by the receivers.

mpi_assert_strict_persistent_collective_ordering
  boolean, default = false. If set to true, then the implementation may assume that all the persistent collective operations are started in the same order across all MPI processes in the group of the communicator. It is required that if this assertion is made on one member of the communicator

`s group, then it must be made on all members of that communicator`s group with the same value.

## Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as

`malloc `or other non-MPICH runtime routines that are themselves not interrupt-safe.

## Notes for Fortran

All MPI routines in Fortran (except for` MPI_WTIME`and` MPI_WTICK`) have an additional argument` ierr`at the end of the argument list.` ierr `is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the` call`statement.

All MPI objects (e.g.,

`MPI_Datatype`,` MPI_Comm`) are of type` INTEGER `in Fortran.

## Errors

All MPI routines (except

`MPI_Wtime`and` MPI_Wtick`) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with` MPI_Comm_set_errhandler`(for communicators),` MPI_File_set_errhandler`(for files), and` MPI_Win_set_errhandler`(for RMA windows). The MPI-1 routine` MPI_Errhandler_set`may be used but its use is deprecated. The predefined error handler` MPI_ERRORS_RETURN`may be used to cause error values to be returned. Note that MPI does` not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS
  No error; MPI routine completed successfully.

MPI_ERR_COMM
  Invalid communicator. A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank`).`

MPI_ERR_INFO
  Invalid Info

MPI_ERR_OTHER
  Other error; use MPI_Error_string`to get more information about this error code.`