MPI_Comm_spawn_multiple(3)         Open MPI         MPI_Comm_spawn_multiple(3)



NAME
       MPI_Comm_spawn_multiple - Spawns multiple binaries, or the same binary
       with multiple sets of arguments.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Comm_spawn_multiple(int count, char *array_of_commands[],
            char **array_of_argv[], int array_of_maxprocs[], MPI_Info
            array_of_info[], int root, MPI_Comm comm, MPI_Comm *intercomm,
            int array_of_errcodes[])


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_COMM_SPAWN_MULTIPLE(COUNT, ARRAY_OF_COMMANDS, ARRAY_OF_ARGV,
            ARRAY_OF_MAXPROCS, ARRAY_OF_INFO, ROOT, COMM, INTERCOMM,
            ARRAY_OF_ERRCODES, IERROR)
            INTEGER   COUNT, ARRAY_OF_INFO(*), ARRAY_OF_MAXPROCS(*), ROOT,
                 COMM, INTERCOMM, ARRAY_OF_ERRCODES(*), IERROR
            CHARACTER*(*) ARRAY_OF_COMMANDS(*), ARRAY_OF_ARGV(COUNT, *)


C++ Syntax
       #include <mpi.h>
       MPI::Intercomm MPI::Intracomm::Spawn_multiple(int count,
            const char* array_of_commands[], const char** array_of_argv[],
            const int array_of_maxprocs[], const MPI::Info array_of_info[],
            int root, int array_of_errcodes[])

       MPI::Intercomm MPI::Intracomm::Spawn_multiple(int count,
            const char* array_of_commands[], const char** array_of_argv[],
            const int array_of_maxprocs[], const MPI::Info array_of_info[],
            int root)


INPUT PARAMETERS
       count     Number of commands (positive integer, significant to MPI only
                 at root -- see NOTES).

       array_of_commands
                 Programs to be executed (array of strings, significant only
                 at root).

       array_of_argv
                 Arguments for commands (array of array of strings,
                 significant only at root).

       array_of_maxprocs
                 Maximum number of processes to start for each command (array
                 of integers, significant only at root).

       array_of_info
                 Info objects telling the runtime system where and how to
                 start processes (array of handles, significant only at root).

       root      Rank of process in which previous arguments are examined
                 (integer).

       comm      Intracommunicator containing group of spawning processes
                 (handle).


OUTPUT PARAMETERS
       intercomm Intercommunicator between original group and the newly
                 spawned group (handle).

       array_of_errcodes
                 One code per process (array of integers).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPI_Comm_spawn_multiple is identical to MPI_Comm_spawn except that it
       can specify multiple executables. The first argument, count, indicates
       the number of executables. The next three arguments are arrays of the
       corresponding arguments in MPI_Comm_spawn. The next argument,
       array_of_info, is an array of info arguments; however, only the first
       argument in that array is used.  Any subsequent arguments in the array
       are ignored because an info argument applies to the entire job that is
       spawned, and cannot be different for each executable in the job.  See
       the INFO ARGUMENTS section for more information.

       For the Fortran version of array_of_argv, the element
       array_of_argv(i,j) is the jth argument to command number i.

       In any language, an application may use the constant MPI_ARGVS_NULL
       (which is likely to be (char ***)0 in C) to specify that no arguments
       should be passed to any commands. The effect of setting individual
       elements of array_of_argv to MPI_ARGV_NULL is not defined. To specify
       arguments for some commands but not others, the commands without
       arguments should have a corresponding argv whose first element is null
       ((char *)0 in C and empty string in Fortran).

       All of the spawned processes have the same MPI_COMM_WORLD. Their ranks
       in MPI_COMM_WORLD correspond directly to the order in which the
       commands are specified in MPI_Comm_spawn_multiple. Assume that m1
       processes are generated by the first command, m2 by the second, etc.
       The processes corresponding to the first command have ranks 0, 1,...,
       m1-1. The processes in the second command have ranks m1, m1+1, ...,
       m1+m2-1. The processes in the third have ranks m1+m2, m1+m2+1, ...,
       m1+m2+m3-1, etc.

       The array_of_errcodes argument is 1-dimensional array of size

             _ count
            \       n ,
            /_ i=1   i

       where i is the ith element of array_of_maxprocs. Command number i
       corresponds to the i contiguous slots in this array from element

                             _              _
             _ i-1          |   _ i          |
            \       n ,  to |  \      n      | -1
            /_ j=1   i      |  /_ j=1  j     |
                            |_              _|

       Error codes are treated as for MPI_Comm_spawn.



INFO ARGUMENTS
       The following keys for info are recognized in "Open MPI". (The reserved
       values mentioned in Section 5.3.4 of the MPI-2 standard are not
       implemented.)


       Key                   Type      Description
       ---                   ----      -----------

       host                  char *    Host on which the process should be spawned.
       wdir                  char *    Directory where the executable is located.
       ompi_prefix           char *    Same as the --prefix command line argument
                                       to mpirun.
       ompi_non_mpi          bool      If set to true, launching a non-MPI
                                       application; the returned communicator
                                       will be MPI_COMM_NULL.


       bool info keys are actually strings but are evaluated as follows: if
       the string value is a number, it is converted to an integer and cast to
       a boolean (meaning that zero integers are false and non-zero values are
       true).  If the string value is (case-insensitive) "yes" or "true", the
       boolean is true.  If the string value is (case-insensitive) "no" or
       "false", the boolean is false.  All other string values are
       unrecognized, and therefore false.


       Note that if any of the info handles have ompi_non_mpi set to true,
       then all info handles must have it set to true.  If some are set to
       true, but others are set to false (or are unset), MPI_ERR_INFO will be
       returned.


       Note that in "Open MPI", the first array location in array_of_info is
       applied to all the commands in array_of_commands.


NOTES
       The argument count is interpreted by MPI only at the root, as is
       array_of_argv. Since the leading dimension of array_of_argv is count, a
       nonpositive value of count at a nonroot node could theoretically cause
       a runtime bounds check error, even though array_of_argv should be
       ignored by the subroutine. If this happens, you should explicitly
       supply a reasonable value of count on the nonroot nodes.

       Calling MPI_Comm_spawn many times would create many sets of children
       with different MPI_COMM_WORLDs, whereas MPI_Comm_spawn_multiple creates
       children with a single MPI_COMM_WORLD, so the two methods are not
       completely equivalent. Also  if you need to spawn multiple executables,
       you may get better performance by using MPI_Comm_spawn_multiple instead
       of calling MPI_Comm_spawn several times.


ERRORS
       Almost all MPI routines return an error value; C routines as the value
       of the function and Fortran routines in the last argument. C++
       functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       Before the error value is returned, the current MPI error handler is
       called. By default, this error handler aborts the MPI job, except for
       I/O function errors. The error handler may be changed with
       MPI_Comm_set_errhandler; 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.


SEE ALSO
       MPI_Comm_spawn(3)
       MPI_Comm_get_parent(3)
       mpirun(1)




1.4.1                            Jan 14, 2010       MPI_Comm_spawn_multiple(3)
