Environment Variables (GNU libgomp)

## 4 OpenMP Environment Variables ¶

The environment variables which beginning with `OMP_` are defined by section 4 of the OpenMP specification in version 4.5 or in a later version of the specification, while those beginning with `GOMP_` are GNU extensions. Most `OMP_` environment variables have an associated internal control variable (ICV).

For any OpenMP environment variable that sets an ICV and is neither `OMP_DEFAULT_DEVICE` nor has global ICV scope, associated device-specific environment variables exist. For them, the environment variable without suffix affects the host. The suffix `_DEV_` followed by a non-negative device number less that the number of available devices sets the ICV for the corresponding device. The suffix `_DEV` sets the ICV of all non-host devices for which a device-specific corresponding environment variable has not been set while the `_ALL` suffix sets the ICV of all host and non-host devices for which a more specific corresponding environment variable is not set.