MPI_STARTALL(3)					     Open MPI					   MPI_STARTALL(3)

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

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 <#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 <#mpi-start> or MPI_Startall is completed  by  a  call	to
       MPI_Wait	 <#mpi-wait>,  MPI_Test	 <#mpi-test>,  or one of the derived functions MPI_Waitany <#mpi-waitany>,
       MPI_Testany  <#mpi-testany>,  MPI_Waitall  <#mpi-waitall>,  MPI_Testall	<#mpi-testall>,	 MPI_Waitsome	<#
       mpi-waitsome>,  MPI_Testsome  <#mpi-testsome>  (these  are  described  in Section 3.7.5 of the MPI Standard
       <https://www.mpi-forum.org/docs/>, “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 <#mpi-start> or MPI_Startall call.

       A persistent request is deallocated by a call to MPI_Request_free <#mpi-request-free> (see Section 3.7.3 of
       the MPI Standard <https://www.mpi-forum.org/docs/>, “Communication Completion”).
       The call to MPI_Request_free <#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  <#mpi-start> can be matched with any receive operation and,
       likewise, a receive operation initiated with MPI_Start <#mpi-start> can receive messages generated  by  any
       send operation.

ERRORS
       Almost  all MPI routines return an error value; C routines as the return result of the function and Fortran
       routines in the last argument.

       Before the error value is returned, the current MPI error handler associated with the communication  object
       (e.g.,  communicator, window, file) is called.  If no communication object is associated with the MPI call,
       then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler.  When
       MPI_COMM_SELF  is  not  initialized  (i.e., before MPI_Init <#mpi-init>/MPI_Init_thread <#mpi-init-thread>,
       after MPI_Finalize <#mpi-finalize>, or when using the Sessions Model  exclusively)  the	error  raises  the
       initial	error  handler.	 The  initial  error  handler can be changed by calling MPI_Comm_set_errhandler <#
       mpi-comm-set-errhandler> on MPI_COMM_SELF when using the World model,  or  the  mpi_initial_errhandler  CLI
       argument	  to   mpiexec	 or   info  key	 to  MPI_Comm_spawn  <#mpi-comm-spawn>/MPI_Comm_spawn_multiple	<#
       mpi-comm-spawn-multiple>.  If no other appropriate error handler has been set, then  the	 MPI_ERRORS_RETURN
       error  handler  is  called  for	MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or  session.  When
	 called on a communicator, it acts as if MPI_Abort <#mpi-abort> was called on that communicator. If called
	 on  a window or file, acts as if MPI_Abort <#mpi-abort> was called on a communicator containing the group
	 of processes in the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler	<#mpi-comm-create-errhandler>	  then	   MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	 <#mpi-file-create-errhandler>	   then	    MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       See the Error Handling section of the MPI-3.1 standard for more information.

       See also:

	  • MPI_Bsend_init <#mpi-bsend-init>

	  • MPI_Rsend_init <#mpi-rsend-init>

	  • MPI_Send_init <#mpi-send-init>

	  • MPI_Ssend_init <#mpi-ssend-init>

	  • MPI_Recv_init <#mpi-recv-init>

	  • MPI_Start <#mpi-start>

	  • MPI_Request_free <#mpi-request-free>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					   MPI_STARTALL(3)
