MPI_Comm_spawn_multiple(3OpenMPI) MPI_Comm_spawn_multiple(3OpenMPI)
NAME
MPI_Comm_spawn_multiple - Spawns multiple binaries, or the same binary with multiple sets of argu-ments. arguments.
ments.
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 executa-bles. executables.
bles. 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 com-mand command
mand 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 values for info are recognized in Open MPI 1.2. (The reserved values mentioned in Sec-tion Section
tion 5.3.4 of the MPI-2 standard are not implemented.)
Key value Type Description
---------- ---- -----------host ----------host
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 theoreti-cally theoretically
cally cause a runtime bounds check error, even though array_of_argv should be ignored by the subrou-tine. subroutine.
tine. 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 per-formance performance
formance 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)
Open MPI 1.2 September 2006 MPI_Comm_spawn_multiple(3OpenMPI)
|