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


C Syntax

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

Fortran Syntax

       INCLUDE 'mpif.h'

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)


       count     Number of commands (positive integer, significant to MPI only  at  root  --  see

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

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

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

                 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).


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

                 One code per process (array of integers).

       IERROR    Fortran only: Error status (integer).


       MPI_Comm_spawn_multiple  is  identical  to  MPI_Comm_spawn(3)  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(3). The
       next argument, array_of_info, is an array of info arguments, one for each executable.  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

       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(3).


       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 *   Comma-separated list of hosts on which
                                       the processes should be spawned.  See
                                       the orte_host man page for an
                                       explanation of how this will be used.
       hostfile               char *   Hostfile containing the hosts on which
                                       the processes are to be spawned. See
                                       the orte_hostfile man page for
                                       an explanation of how this will be
       add-host               char *   Add the specified hosts to the list of
                                       hosts known to this job and use it for
                                       the associated processes. This will be
                                       used similarly to the -host option.
       add-hostfile           char *   Hostfile containing hosts to be added
                                       to the list of hosts known to this job
                                       and use it for the associated
                                       process. This will be used similarly
                                       to the -hostfile option.
       wdir                   char *   Directory where the executable is
                                       located. If files are to be
                                       pre-positioned, then this location is
                                       the desired working directory at time
                                       of execution - if not specified, then
                                       it will automatically be set to
       ompi_prefix            char *   Same as the --prefix command line
                                       argument to mpirun.
       ompi_preload_binary    bool     If set to true, pre-position the
                                       specified executable onto the remote
                                       host. A destination directory must
                                       also be provided.
       ompi_preload_files     char *   A comma-separated list of files that
                                       are to be pre-positioned in addition
                                       to the executable.  Note that this
                                       option does not depend upon
                                       ompi_preload_binary - files can
                                       be moved to the target even if an
                                       executable is not moved.
       ompi_stdin_target   char* Comma-delimited list of ranks to
                                       receive stdin when forwarded.
       ompi_non_mpi           bool     If set to true, launching a non-MPI
                                       application; the returned communicator
                                       will be MPI_COMM_NULL. Failure to set
                                       this flag when launching a non-MPI
                                       application will cause both the child
                                       and parent jobs to "hang".
       ompi_param             char *   Pass an OMPI MCA parameter to the
                                       child job.  If that parameter already
                                       exists in the environment, the value
                                       will be overwritten by the provided
       mapper                    char*  Mapper to be used for this job
       map_by                    char*  Mapping directive indicating how
                                       processes are to be mapped (slot,
                                       node, socket, etc.).
       rank_by                   char *  Ranking directive indicating how
                                       processes are to be ranked (slot,
                                       node, socket, etc.).
       bind_to                    char *  Binding directive indicating how
                                       processes are to be bound (core, slot,
                                       node, socket, etc.).
       path                         char*  List of directories to search for
                                       the executable
       npernode                 char* Number of processes to spawn on
                                       each node of the allocation
       pernode                   bool  Equivalent to npernode of 1
       ppr                          char* Spawn specified number of processes
                                      on each of the identified object type
       env                         char*  Newline-delimited list of envars to
                                      be passed to the spawned procs

       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

       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.


       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.

       Similar to MPI_Comm_spawn(3), it is the application's  responsibility  to  terminate  each
       individual set of argv in the array_of_argv argument.  In C, each argv array is terminated
       by a NULL pointer.  In Fortran, each argv array is terminated by  an  empty  string  (note
       that  compilers  will  not  automatically  insert  this blank string; the application must
       ensure to have enough space for an empty string entry as the last element of the array).

       Other  restrictions  apply  to  the  array_of_argv  parameter;   see   MPI_Comm_spawn(3)'s
       description of the argv parameter for more details.

       Calling  MPI_Comm_spawn(3)  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(3) several times.


       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.