Ubuntu Manpage: MPI_Startall - Starts a collection of requests.

Provided by: openmpi-doc_4.1.6-7ubuntu2_all

NAME

       MPI_Startall - Starts a collection of requests.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Startall(int count, MPI_Request array_of_requests[])

Fortran Syntax

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_STARTALL(COUNT, ARRAY_OF_REQUESTS, IERROR)
            INTEGER   COUNT, ARRAY_OF_REQUESTS(*), IERROR

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Startall(count, array_of_requests, ierror)
            INTEGER, INTENT(IN) :: count
            TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(count)
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax

       #include <mpi.h>
       static void Prequest::Startall(int count, Prequest array_of_requests[])

INPUT PARAMETER

       count     List length (integer).

INPUT/OUTPUT PARAMETER

       array_of_requests
                 Array of requests (array of handle).

OUTPUT PARAMETER

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

Starts all communications associated with requests in array_of_requests. A call to MPI_Startall(count,
array_of_requests) has the same effect as calls to MPI_Start (&array_of_requests[i]), executed for i=0
,..., count-1, in some arbitrary order.

A communication started with a call to MPI_Start or MPI_Startall is completed by a call to MPI_Wait,
MPI_Test, or one of the derived functions MPI_Waitany, MPI_Testany, MPI_Waitall, MPI_Testall,
MPI_Waitsome, MPI_Testsome (these are described in Section 3.7.5 of the MPI-1 Standard, "Multiple
Completions"). The request becomes inactive after successful completion by such a call. The request is
not deallocated, and it can be activated anew by another MPI_Start or MPI_Startall call.

A persistent request is deallocated by a call to MPI_Request_free (see Section 3.7.3 of the MPI-1
Standard, "Communication Completion").

The call to MPI_Request_free can occur at any point in the program after the persistent request was
created. However, the request will be deallocated only after it becomes inactive. Active receive requests
should not be freed. Otherwise, it will not be possible to check that the receive has completed. It is
preferable, in general, to free requests when they are inactive. If this rule is followed, then the
persistent communication request functions will be invoked in a sequence of the form,

Create (Start Complete)* Free

where * indicates zero or more repetitions. If the same communication object is used in several
concurrent threads, it is the user's responsibility to coordinate calls so that the correct sequence is
obeyed.

A send operation initiated with MPI_Start can be matched with any receive operation and, likewise, a
receive operation initiated with MPI_Start can receive messages generated by any send operation.

ERRORS

       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.