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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, signifi-
cant 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
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 ele-
ments of array_of_argv to MPI_ARGV_NULL is not defined. To specify
arguments for some commands but not others, the commands without argu-
ments 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 com-
mands are specified in MPI_Comm_spawn_multiple. Assume that m1 pro-
cesses 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 cor-
responds 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.
host char * Host on which the process should be spawned.
wdir char * Directory where the executable is located.
Note that in Open MPI 1.2, 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 sup-
ply 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 com-
pletely 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++ func-
tions 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)
Open MPI 1.2 September 200MPI_Comm_spawn_multiple(3OpenMPI)
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