---
name: "MPI_Startall"
section: "3"
platform: "linux"
package: "openmpi"
version: "5.0.11-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/MPI_Startall"
---

# 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* (&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 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 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 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\_thread*, after *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* 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\_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* was called on that communicator. If called on a window or file, acts as if *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* then *MPI\_Comm\_set\_errhandler*

- •

  *MPI\_File\_create\_errhandler* then *MPI\_File\_set\_errhandler*

- •

  *MPI\_Session\_create\_errhandler* then *MPI\_Session\_set\_errhandler* or at *MPI\_Session\_init*

- •

  *MPI\_Win\_create\_errhandler* then *MPI\_Win\_set\_errhandler*

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

See the *MPI man page* for a full list of *MPI error codes*.

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

**SEE ALSO:**

- •

  *MPI\_Bsend\_init*

- •

  *MPI\_Rsend\_init*

- •

  *MPI\_Send\_init*

- •

  *MPI\_Ssend\_init*

- •

  *MPI\_Recv\_init*

- •

  *MPI\_Start*

- •

  *MPI\_Request\_free*

## COPYRIGHT

2003-2026, The Open MPI Community