X06 Chapter Contents
X06 Chapter Introduction
NAG Library Manual

# NAG Library Routine DocumentX06ABF

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

## 1  Purpose

X06ABF returns the number of OpenMP threads in the current team.

## 2  Specification

 FUNCTION X06ABF ( )
 INTEGER X06ABF

## 3  Description

X06ABF, for multi-threaded implementations, returns the number of OpenMP threads in the current team. If the number of threads is deemed critical then you are advised to use X06ABF to retrieve this value as it may be less than that requested with either a call to X06AAF, your OMP_NUM_THREADS environment variable value or by using a num_threads clause on an OpenMP parallel directive.
The number of threads actually in use in a parallel region is dependent on several factors. Please refer to Section 4 for a full description of how the number of threads is chosen for a particular parallel region.
If this routine is called from a sequential part of a multi-threaded program then it will return the value $1$.
In serial implementations of the NAG Library this routine will always return $1$. See the X06 Chapter Introduction for a discussion of the behaviour of these routines when called in serial.

## 4  References

OpenMP Specifications http://openmp.org/wp/OpenMP-Specifications
Chapman B, Jost G and van der Pas R (2008) Using OpenMP Portable Shared Memory Parallel Programming The MIT Press

None.

None.

Not applicable.

## 8  Parallelism and Performance

X06ABF is not threaded in any implementation.