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NAME

       MPI_Waitsome -  Waits for some given communications to complete

SYNOPSIS

       #include <mpi.h>
       int MPI_Waitsome(int count, MPI_Request* reqs, int *ndone,
                       int *indices, MPI_Status *stats)

INPUT PARAMETERS

       incount
              - length of array_of_requests (integer)
       reqs   - array of requests (array of handles)

OUTPUT PARAMETERS

       ndone  - number of completed requests (integer)
       indices
              - array of indices of operations that completed (array of integers)
       stats  -  array  of status objects for operations that completed (array of Status), or the
              MPI constant 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 .

NOTE ON STATUS FOR SEND OPERATIONS

       For send operations, the only use of status is for MPI_Test_cancelled  in  the  case  that
       there is an error, in which case the MPI_ERROR field of status will be set.

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

       If an error occurs in an MPI function, the current MPI error handler is called  to  handle
       it.   By default, this error handler aborts the MPI job.  The error handler may be changed
       with MPI_Errhandler_set ; the predefined error handler MPI_ERRORS_RETURN may  be  used  to
       cause  error values to be returned (in C and Fortran; this error handler is less useful in
       with the C++ MPI bindings.   The  predefined  error  handler  MPI::ERRORS_THROW_EXCEPTIONS
       should  be  used in C++ if the error value needs to be recovered).  Note that MPI does not
       guarantee that an MPI program can continue past an error.

       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.  The C++ bindings for
       MPI do not return error  values;  instead,  error  values  are  communicated  by  throwing
       exceptions of type MPI::Exception (but not by default).  Exceptions are only thrown if the
       error value is not MPI::SUCCESS .

       Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return
       upon an error, there will be no way to recover what the actual error value was.
       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_REQUEST
              -  Invalid  MPI_Request  ;  either  null  or,  MPI_REQUEST_NULL  , in the case of a
              MPI_Start or MPI_Startall , not a persistent request.
       MPI_ERR_COUNT
              - Invalid count argument.  Count arguments must be non-negative; a count of zero is
              often valid.
       MPI_ERR_ARG
              -  Invalid  argument.  Some argument is invalid and is not identified by a specific
              error class.  This is typically a NULL pointer or other such error.

       MPI_ERR_IN_STATUS
              - The actual error value is in the MPI_Status argument.  Note that  if  this  error
              occurs  and  MPI_STATUS_IGNORE  or  MPI_STATUSES_IGNORE  was  used  as  the  status
              argument, the actual error will be lost. This error class is returned only from the
              multiple-completion   routines   (  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  error and complete) or
              MPI_ERR_PENDING to indicate that the request 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)?  LAM/MPI has chosen 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 .

MORE INFORMATION

       For more information, please see the official MPI Forum web site, which contains the  text
       of both the MPI-1 and MPI-2 standards.  These documents contain detailed information about
       each MPI function (most of which is not duplicated in these man pages).

       http://www.mpi-forum.org/

ACKNOWLEDGEMENTS

       The LAM Team would like the thank the MPICH Team for the handy  program  to  generate  man
       pages   ("doctext"  from  ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz  ),  the  initial
       formatting, and some initial text for most of the MPI-1 man pages.

LOCATION

       waitsome.c