# NAG Library Function Document

## 1Purpose

nag_omp_get_num_threads (x06abc) returns the number of OpenMP threads in the current team.

## 2Specification

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## 3Description

nag_omp_get_num_threads (x06abc), 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 nag_omp_get_num_threads (x06abc) to retrieve this value as it may be less than that requested with either a call to nag_omp_set_num_threads (x06aac), 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 function is called from a sequential part of a multi-threaded program then it will return the value $1$.
In serial implementations of the NAG C Library this function will always return $1$. See the x06 Chapter Introduction for a discussion of the behaviour of these functions when called in serial.

## 4References

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

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