MPI_Init

Initialize the MPI execution environment

Synopsis


#include "mpi.h"
int MPI_Init(argc,argv)
int  *argc;
char ***argv;

Input Parameters

argc - Pointer to the number of arguments

argv - Pointer to the argument vector

Command line arguments

MPI specifies no command-line arguments but does allow an MPI implementation to make use of them.

-mpiqueue - print out the state of the message queues when MPI_FINALIZE is called. All processors print; the output may be hard to decipher. This is intended as a debugging aid.

-mpiversion - print out the version of the implementation (not of MPI), including the arguments that were used with configure.

-mpinice nn - Increments the nice value by nn (lowering the priority of the program by nn). nn must be positive (except for root). Not all systems support this argument; those that do not will ignore it.

-mpedbg - Start a debugger in an xterm window if there is an error (either detected by MPI or a normally fatal signal). This works only if MPICH was configured with -mpedbg.

-mpipktsize nn - Set the message length where the ADI changed to the long message protocol to nn. This only works if MPICH was configured with -var_pkt.

The following options are available only on the Chameleon device and devices built with debugging code. Normally, these should only be used by MPICH implementors when debugging new ports.

-mpichdebug - Print out the Chameleon device operations

-mpidbfile filename - Like mpichdebug, but sends the output to the specified file. If the filename contains a %d, then that part of the filename is replaced with the rank in MPI_COMM_WORLD. For example,


   -mpidbfile log.%d

writes to log.0, log.1, etc.

-mpichmemdebug - (Chameleon device only) Print out a list of unreclaimed memory. This requires that MPI be built with the -DMPIR_DEBUG_MEM switch. This is intended for debugging the MPI implementation itself.

-mpimem - If MPICH was built with -DMPIR_DEBUG_MEM, this checks all malloc and free operations (internal to MPICH) for signs of injury to the memory allocation areas.

-mpichmsg - Print out the number of messages received, by category, when the program exits.

Notes

Note that the Fortran binding for this routine has only the error return argument (MPI_INIT(ierror))

Because the Fortran and C versions of MPI_Init are different, there is a restriction on who can call MPI_Init. The version (Fortran or C) must match the main program. That is, if the main program is in C, then the C version of MPI_Init must be called. If the main program is in Fortran, the Fortran version must be called.

On exit from this routine, all processes will have a copy of the argument list. This is not required by the MPI standard, and truely portable codes should not rely on it. This is provided as a service by this implementation (an MPI implementation is allowed to distribute the command line arguments but is not required to).

Command line arguments are not provided to Fortran programs. More precisely, non-standard Fortran routines such as getarg and iargc have undefined behavior in MPI and in this implementation.

The MPI standard does not say what a program can do before an MPI_INIT or after an MPI_FINALIZE. In the MPICH implementation, you should do as little as possible. In particular, avoid anything that changes the external state of the program, such as opening files, reading standard input or writing to standard output.

Signals used

The MPI standard requires that all signals used be documented. The MPICH implementation itself uses no signals, but some of the software that MPICH relies on may use some signals. The list below is partial and should be independantly checked if you (and any package that you use) depend on particular signals.

IBM POE/MPL for SP2

SIGHUP, SIGINT, SIGQUIT, SIGFPE, SIGSEGV, SIGPIPE, SIGALRM, SIGTERM, SIGIO

-mpedbg switch

SIGQUIT, SIGILL, SIGFPE, SIGBUS, SIGSEGV, SIGSYS

Meiko CS2

SIGUSR2

ch_p4 device

SIGUSR1

Intel Paragon (ch_nx and nx device)

SIGUSR2

Shared Memory (ch_shmem device)

SIGCHLD

Note that if you are using software that needs the same signals, you may find that there is no way to use that software with the MPI implementation. The signals that cause the most trouble for applications include SIGIO, SIGALRM, and SIGPIPE. For example, using SIGIO and SIGPIPE may prevent X11 routines from working.

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_Errhandler_set; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error.

MPI_SUCCESS - No error; MPI routine completed successfully.

MPI_ERR_OTHER - This error class is associated with an error code that indicates that an attempt was made to call MPI_INIT a second time. MPI_INIT may only be called once in a program.

Location:init.c