|count||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).|
|root||Rank of process in which previous arguments are examined (integer).|
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 applications 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.
|1.10.2||MPI_COMM_SPAWN_MULTIPLE (3)||Jan 21, 2016|