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MPI_Comm_spawn_multiple - Spawns multiple binaries, or the same
binary with multiple sets of arguments.
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,
! or the older form: INCLUDE ’mpif.h’
MPI_COMM_SPAWN_MULTIPLE(COUNT, ARRAY_OF_COMMANDS, ARRAY_OF_ARGV,
ARRAY_OF_MAXPROCS, ARRAY_OF_INFO, ROOT, COMM, INTERCOMM,
INTEGER COUNT, ARRAY_OF_INFO(*), ARRAY_OF_MAXPROCS(*), ROOT,
COMM, INTERCOMM, ARRAY_OF_ERRCODES(*), IERROR
CHARACTER*(*) ARRAY_OF_COMMANDS(*), ARRAY_OF_ARGV(COUNT, *)
MPI_Comm_spawn_multiple(count, array_of_commands, array_of_argv,
array_of_maxprocs, array_of_info, root, comm, intercomm,
INTEGER, INTENT(IN) :: count, array_of_maxprocs(*), root
CHARACTER(LEN=*), INTENT(IN) :: array_of_commands(*)
CHARACTER(LEN=*), INTENT(IN) :: array_of_argv(count, *)
TYPE(MPI_Info), INTENT(IN) :: array_of_info(*)
TYPE(MPI_Comm), INTENT(IN) :: comm
TYPE(MPI_Comm), INTENT(OUT) :: intercomm
INTEGER :: array_of_errcodes(*)
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
- Number of commands (positive integer, significant
to MPI only at root -- see NOTES).
- 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).
- Rank of process in which previous arguments are examined
- Intracommunicator containing group of spawning processes
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.
- Intercommunicator between original
group and the newly spawned group (handle).
- One code per
process (array of integers).
- Fortran only: Error status (integer).
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
\ 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).
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
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
MPI-3.1 implies (but does not directly state) that the argument
array_of_commands must be an array of strings of length count. Unlike the
array_of_argv parameter, array_of_commands does not need to be terminated
with a NULL pointer in C or a blank string in Fortran. Older versions of
Open MPI required that array_of_commands be terminated with a blank string
in Fortran; that is no longer required in this version of Open MPI.
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
Almost all MPI routines return an error value; C routines
as the value of the function and Fortran routines in the last argument.
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.
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