Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
MPI_Waitsome(3)			      MPI		       MPI_Waitsome(3)

NAME
       MPI_Waitsome -  Waits for some given MPI	Requests to complete

SYNOPSIS
       int MPI_Waitsome(int incount, MPI_Request array_of_requests[],
		       int *outcount, int array_of_indices[],
		       MPI_Status array_of_statuses[])

INPUT PARAMETERS
       incount
	      -	length of array_of_requests (integer)
       array_of_requests
	      -	array of requests (array of handles)

OUTPUT PARAMETERS
       outcount
	      -	number of completed requests (integer)
       array_of_indices
	      -	 array of indices of operations	that completed (array of inte-
	      gers)
       array_of_statuses
	      -	array of status	objects	for operations that  completed	(array
	      of Status).  May be MPI_STATUSES_IGNORE .

NOTES
       The  array  of  indicies	are in the range 0 to incount -	1 for C	and in
       the range 1 to incount for Fortran.

       Null requests are ignored; if all requests are null, then  the  routine
       returns with outcount set to MPI_UNDEFINED .

       While it	is possible to list a request handle more than once in the ar-
       ray_of_requests,	such an	action is considered erroneous and  may	 cause
       the program to unexecpectedly terminate or produce incorrect results.

       MPI_Waitsome  provides  an  interface much like the Unix	select or poll
       calls and, in a high qualilty implementation, indicates all of the  re-
       quests  that  have  completed  when  MPI_Waitsome  is called.  However,
       MPI_Waitsome only guarantees that at least one request  has  completed;
       there  is no guarantee that all completed requests will be returned, or
       that the	entries	in array_of_indices will be in increasing order. Also,
       requests	 that are completed while MPI_Waitsome is executing may	or may
       not be returned,	depending on the timing	of the completion of the  mes-
       sage.

NOTES ON THE MPI_STATUS	ARGUMENT
       The MPI_ERROR field of the status return	is only	set if the return from
       the MPI routine is MPI_ERR_IN_STATUS .  That error class	 is  only  re-
       turned  by  the	routines  that	take  an  array	 of status arguments (
       MPI_Testall , MPI_Testsome , MPI_Waitall	, and MPI_Waitsome ).  In  all
       other  cases,  the  value  of  the MPI_ERROR field in the status	is un-
       changed.	 See section 3.2.5 in the MPI-1.1 specification	for the	 exact
       text.

       For  send  operations, the only use of status is	for MPI_Test_cancelled
       or in the case that there is an error in	one of the four	routines  that
       may  return  the	 error	class  MPI_ERR_IN_STATUS  ,  in	which case the
       MPI_ERROR field of status will be set.  In that case, the value will be
       set  to	MPI_SUCCESS  for  any send or receive operation	that completed
       successfully, or	MPI_ERR_PENDING	for any	operation  which  has  neither
       failed nor completed.

THREAD AND INTERRUPT SAFETY
       This  routine  is  thread-safe.	 This  means  that this	routine	may be
       safely used by multiple threads without the need	for any	 user-provided
       thread  locks.  However,	the routine is not interrupt safe.  Typically,
       this is due to the use of memory	allocation routines such as malloc  or
       other  non-MPICH	 runtime  routines  that are themselves	not interrupt-
       safe.

NOTES FOR FORTRAN
       All MPI routines	in Fortran (except for MPI_WTIME and MPI_WTICK )  have
       an  additional  argument	ierr at	the end	of the argument	list.  ierr is
       an integer and has the same meaning as the return value of the  routine
       in  C.	In Fortran, MPI	routines are subroutines, and are invoked with
       the call	statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm )	are of type INTEGER in
       Fortran.

ERRORS
       All  MPI	 routines  (except  MPI_Wtime  and MPI_Wtick ) return an error
       value; C	routines as the	value of the function and Fortran routines  in
       the last	argument.  Before the value is returned, the current MPI error
       handler is called.  By default, this error handler aborts the MPI  job.
       The error handler may be	changed	with MPI_Comm_set_errhandler (for com-
       municators), MPI_File_set_errhandler (for files),  and  MPI_Win_set_er-
       rhandler	 (for  RMA windows).  The MPI-1	routine	MPI_Errhandler_set may
       be used but its	use  is	 deprecated.   The  predefined	error  handler
       MPI_ERRORS_RETURN  may  be  used	 to cause error	values to be returned.
       Note that MPI does not guarentee	that an	MPI program can	continue  past
       an  error;  however, MPI	implementations	will attempt to	continue when-
       ever possible.

       MPI_SUCCESS
	      -	No error; MPI routine completed	successfully.
       MPI_ERR_REQUEST
	      -	Invalid	MPI_Request .  Either  null  or,  in  the  case	 of  a
	      MPI_Start	or MPI_Startall	, not a	persistent request.
       MPI_ERR_ARG
	      -	Invalid	argument.  Some	argument is invalid and	is not identi-
	      fied by a	specific error class (e.g., MPI_ERR_RANK ).
       MPI_ERR_IN_STATUS
	      -	The actual error value is in the  MPI_Status  argument.	  This
	      error  class  is returned	only from the multiple-completion rou-
	      tines ( MPI_Testall , MPI_Testany	, MPI_Testsome , MPI_Waitall ,
	      MPI_Waitany  ,  and  MPI_Waitsome	).  The	field MPI_ERROR	in the
	      status argument contains the error value or MPI_SUCCESS (no  er-
	      ror  and	complete)  or MPI_ERR_PENDING to indicate that the re-
	      quest has	not completed.	The MPI	Standard does not specify what
	      the  result of the multiple completion routines is when an error
	      occurs.  For example, in an MPI_WAITALL ,	does the routine  wait
	      for  all	requests to either fail	or complete, or	does it	return
	      immediately (with	the MPI	definition of immediately, which means
	      independent  of actions of other MPI processes)?	MPICH has cho-
	      sen to make the return  immediate	 (alternately,	local  in  MPI
	      terms),  and  to use the error class MPI_ERR_PENDING (introduced
	      in MPI 1.1) to indicate which requests have not  completed.   In
	      most  cases,  only one request with an error will	be detected in
	      each call	to an MPI routine that tests multiple  requests.   The
	      requests	that have not been processed (because an error occured
	      in one of	the requests) will have	their MPI_ERROR	 field	marked
	      with MPI_ERR_PENDING .

LOCATION
       src/mpi/pt2pt/waitsome.c

				   9/20/2012		       MPI_Waitsome(3)

NAME | SYNOPSIS | INPUT PARAMETERS | OUTPUT PARAMETERS | NOTES | NOTES ON THE MPI_STATUS ARGUMENT | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS | LOCATION

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=MPI_Waitsome&sektion=3&manpath=FreeBSD+13.0-RELEASE+and+Ports>

home | help