What is MPI_Add_error_class?
MPI library
MPI, short for Message Passing Interface, is a library that allows you to write parallel programs in Fortran77 or C. The library uses common operating system services to exchange information among the parallel processes it creates.
MPI_Add_error_class
Some users may want to create additional libraries on top of an existing MPI implementation, and these libraries may have their own sets of error codes and classes. For this purpose, MPI offers the MPI_Add_error_class function to create a new error class and return the value for it.
The value is set by the MPI implementation, and not by the user, in order to avoid conflicts with existing error codes and classes.
Syntax
int MPI_Add_error_class(int *errorclass)
Parameters
errorclassis an output parameter representing the value for the new error class.
Return value
If unsuccessful, the function returns an error. The error aborts the MPI job by default.
-
In case of success,
MPI_Add_error_classreturnsMPI_SUCCESS, the value returned upon successful termination of any MPI routine. -
In case of other errors,
MPI_ERR_OTHERis returned.MPI_Error_stringcan be used to get more information about this error code.
Example
The example below shows how we can use the MPI_Add_error_class function to introduce custom error classes in an MPI implementation:
#include "mpi.h"#include <stdio.h>#include <stdlib.h>#include <string.h>/* Create NCLASSES new classes, each with 4 codes (120 total) */#define NCLASSES 30#define NCODES 4int main( int argc, char *argv[] ){int newclass[NCLASSES], newcode[NCLASSES][NCODES];int i, j;MPI_Init( &argc, &argv );/* Initialize the new codes */for (i=0; i<NCLASSES; i++) {MPI_Add_error_class( &newclass[i] );for (j=0; j<NCODES; j++) {MPI_Add_error_code( newclass[i], &newcode[i][j] );}}}
- We define the macros
NCLASSESandNCODESto define the number of classes and the error codes within each class (lines 7-8). - We then initialize the
newcodeandnewclassarrays to represent the error classes and their codes (line 12). - In the
forloop, we use theMPI_Add_error_classmethod to create a new error class, and within the loop, we also assign each class with its error codes using theMPI_Add_error_codemethod (line 18, 20).
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