---
name: "MPI_T_pvar_start.openmpi"
section: "3"
platform: "linux"
package: "openmpi-doc"
version: "5.0.7-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/MPI_T_pvar_start.openmpi"
---

# MPI\_T\_pvar\_start.openmpi(3)

*MPI\_T\_pvar\_start*, *MPI\_T\_pvar\_stop* - Start/stop a performance variable

## SYNTAX

### C Syntax

```
#include <mpi.h>
int MPI_T_pvar_start(MPI_T_pvar_session session, MPI_T_pvar_handle handle)
int MPI_T_pvar_stop(MPI_T_pvar_session session, MPI_T_pvar_handle handle)
```

## INPUT PARAMETERS

- •

  **session**: Performance experiment session.

- •

  **handle**: Performance variable handle.

## DESCRIPTION

*MPI\_T\_pvar\_start* starts the performance variable with the handle specified in *handle*. The special value MPI\_T\_PVAR\_ALL\_HANDLES can be passed in *handle* to start all non-continuous handles in the session specified in *session*.

*MPI\_T\_pvar\_stop* stops the performance variable with the handle specified in *handle*. The special value MPI\_T\_PVAR\_ALL\_HANDLES can be passed in *handle* to stop all non-continuous handles in the session specified in *session*.

Continuous performance variables can neither be started nor stopped.

## ERRORS

*MPI\_T\_pvar\_start* and MPI\_T\_pvar\_stop() will fail if:

- •

  **MPI\_T\_ERR\_NOT\_INITIALIZED**: The MPI Tools interface not initialized

- •

  **MPI\_T\_ERR\_INVALID\_SESSION**: Session parameter is not a valid session

- •

  **MPI\_T\_ERR\_INVALID\_HANDLE**: Invalid handle or handle not associated with the session

- •

  **MPI\_T\_ERR\_PVAR\_NO\_STARTSTOP**: The variable cannot be started or stopped

**SEE ALSO:**

- •

  *MPI\_T\_pvar\_get\_info*

## COPYRIGHT

2003-2025, The Open MPI Community