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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[], const int array_of_maxprocs[], const 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
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_preload_files_dest_dir.
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
value.
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 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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