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MPI_Comm_spawn_multiple - Spawns multiple binaries, or the same binary
with multiple sets of arguments.
#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[])
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, *)
#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 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).
- 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).
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 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(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 used.
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 processes.
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_preload_files_dest_dir.
ompi_prefix char * Same as the --prefix command line
argument
to mpirun.
ompi_local_slave bool If set to true, launch the specified
process
as a local slave to the calling
process.
The new process will only be
known to the caller,
and will only be able to communicate
with the caller.
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_dest_dir char * Target directory where pre-positioned
files
are to be placed.
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_preload_files_src_dir char * Source directory where files
and executables
that are to be pre-positioned
can be found. If
not specified, the current working
directory
will be used.
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 value.
map_bynode bool If set to true, the processes
are mapped bynode.
If set to false, the processes
are mapped byslot.
By default, mapping is determined
by the default
mapping policy set when the job
was started.
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.
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.
MPI_Comm_spawn(3)
MPI_Comm_get_parent(3)
mpirun(1)
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