MPI\_T\_PVAR\_READRESET(3) Open MPI MPI\_T\_PVAR\_READRESET(3)

MPI\_T\_pvar\_readreset — Atomically read and reset the value of a performance variable

# [SYNTAX](#SYNTAX)

## [C Syntax](#C_Syntax)

```
#include <mpi.h>
int MPI_T_pvar_readreset(MPI_T_pvar_session session, MPI_T_pvar_handle handle, const void *buf)
```

# [INPUT PARAMETERS](#INPUT_PARAMETERS)

- **session**: Performance experiment session.
- **handle**: Performance variable handle.
- **buf**: Initial address of storage location for variable value.

# [DESCRIPTION](#DESCRIPTION)

MPI\_T\_pvar\_readreset atomically queries and resets the value of a performance variable bound to the handle specified by *handle* in the session specified by *session*. The result is stored in the buffer pointed to by *buf*. This function can only be used with performance variables that are atomic and not readonly. The caller must ensure that the buffer pointed to by *buf* is large enough to hold the entire value of the performance variable.

# [ERRORS](#ERRORS)

MPI\_T\_pvar\_readreset will fail if:

- **MPI\_T\_ERR\_NOT\_INITIALIZED**: The MPI Tools interface not initialized
- **MPI\_T\_ERR\_INVALID\_HANDLE**: The handle is invalid or not associated with the session
- **MPI\_T\_ERR\_INVALID\_SESSION**: Session argument is not a valid session
- **MPI\_T\_ERR\_PVAR\_NO\_ATOMIC**: Variable cannot be read and written atomically
- **MPI\_T\_ERR\_PVAR\_NO\_WRITE**: Variable cannot be reset

**See also:**

- MPI\_T\_pvar\_handle\_alloc &lt;#mpi-t-pvar-handle-alloc&gt;
- MPI\_T\_pvar\_get\_info &lt;#mpi-t-pvar-get-info&gt;
- MPI\_T\_pvar\_session\_create &lt;#mpi-t-pvar-session-create&gt;
- MPI\_T\_pvar\_read &lt;#mpi-t-pvar-read&gt;
- MPI\_T\_pvar\_reset &lt;#mpi-t-pvar-reset&gt;

# [Copyright](#Copyright)

2003-2026, The Open MPI Community

September 16, 2026

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Document: MPI_T_pvar_readreset(3) from openmpi-cuda-12.6 5.0.11-r1 (Chainguard OS)
Source: https://github.com/open-mpi/ompi