OpenMP 3.1 is fully supported. Some features from more recent OpenMP specifications are also supported; check the Release Notes for details.
When using the IEEE arithmetic support modules, the IEEE modes (rounding,
halting and underflow) are propagated into spawned OpenMP threads at the
beginning of a PARALLEL construct, and any IEEE flag that are set by an
OpenMP thread is passed back to the parent thread at the end of the
PARALLEL construct.
The following table lists the OpenMP environment variables with their default values and, if applicable, their limits.
| Environment Variable | Default | Limits |
OMP_NUM_THREADS | number of cores | 1-32768 |
OMP_DYNAMIC | False | true or false |
OMP_NESTED | False | true or false |
OMP_STACKSIZE | 0 | <1GB (32-bit) or 16GB (64-bit) |
OMP_WAIT_POLICY | None | active or passive |
OMP_MAX_ACTIVE_LEVELS | 1 | 1-64 |
OMP_THREAD_LIMIT | 32768 | 1-32768 |
OMP_CANCELLATION | False | true or false |
Note that although the NAG runtime supports up to 32768 threads, operating system limits may prevent usage of so many.
OpenMP is not compatible with the -coarray=cosmp option.