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MPI_INFO_GET_STRING(3) Open MPI MPI_INFO_GET_STRING(3)

MPI_Info_get_string — Retrieves the value associated with a key in an info object.

SYNTAX

C Syntax

#include <mpi.h>
int MPI_Info_get_string(MPI_Info info, const char *key, int *buflen, char *value, int *flag)


Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_INFO_GET_STRING(INFO, KEY, BUFLEN, VALUE, FLAG, IERROR)


     INTEGER INFO, BUFLEN, IERROR


     CHARACTER*(*) KEY, VALUE


     LOGICAL FLAG


Fortran 2008 Syntax

USE mpi_f08
MPI_Info_get_string(info, key, buflen, value, flag, ierror)


     TYPE(MPI_Info), INTENT(IN) :: info


     CHARACTER(LEN=*), INTENT(IN) :: key


     INTEGER, INTENT(INOUT) :: buflen


     CHARACTER(LEN=valuelen), INTENT(OUT) :: value


     LOGICAL, INTENT(OUT) :: flag


     INTEGER, OPTIONAL, INTENT(OUT) :: ierror


INPUT PARAMETERS

  • info: Info object (handle).
  • key: Key (string).

OUTPUT PARAMETER

  • buflen On entry, length of value arg. On return, set to required size to: hold value string (integer).
  • value: Value (string).
  • flag: Returns true if key defined, false if not (boolean).
  • ierror: Fortran only: Error status (integer).

DESCRIPTION

MPI_Info_get_string retrieves the value associated with key from info, if any. If such a key exists in info, it sets flag to true and returns the value in value, otherwise it sets flag to false and leaves value unchanged. buflen on input is the size of the provided buffer, for the output of buflen it is the size of the buffer needed to store the value string. If the buflen passed into the function is less than the actual size needed to store the value string (including null terminator in C), the value is truncated. On return, the value of buflen will be set to the required buffer size to hold the value string. If buflen is set to 0, value is not changed. In C, buflen includes the required space for the null terminator. In C, this function returns a null terminated string in all cases where the buflen input value is greater than 0.

If key is larger than MPI_MAX_INFO_KEY, the call is erroneous.

ERRORS

Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

Open MPI includes three predefined error handlers that can be used:

  • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.
  • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.
  • MPI_ERRORS_RETURN Returns an error code to the application.

MPI applications can also implement their own error handlers by calling:

  • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
  • MPI_File_create_errhandler then MPI_File_set_errhandler
  • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
  • MPI_Win_create_errhandler then MPI_Win_set_errhandler

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information.

SEE ALSO:

  • MPI_Info_create
  • MPI_Info_delete
  • MPI_Info_dup
  • MPI_Info_free
  • MPI_Info_get_nkeys
  • MPI_Info_get_nthkey
  • MPI_Info_set



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December 2, 2024