Add set_omp_num_threads hook from EESSI#133

eessi/testsuite/hooks.py

@@ -2,6 +2,7 @@
 Hooks for adding tags, filtering and setting job resources in ReFrame tests
 """
 import math
+import os
 import shlex
 import warnings
 
@@ -680,6 +681,15 @@ def set_compact_thread_binding(test: rfm.RegressionTest):
     log(f'Set environment variable KMP_AFFINITY to {test.env_vars["KMP_AFFINITY"]}')
 
 
+def set_omp_num_threads(test: rfm.RegressionTest):
+    """
+    Set default number of OpenMP threads equal to number of CPUs per task,
+    unless OMP_NUM_THREADS is already set
+    """
+    test.env_vars['OMP_NUM_THREADS'] = os.getenv('OMP_NUM_THREADS', test.num_cpus_per_task)
+    log(f'Set environment variable OMP_NUM_THREADS to {test.env_vars["OMP_NUM_THREADS"]}')
+
+
 def _check_always_request_gpus(test: rfm.RegressionTest):
     """
     Make sure we always request enough GPUs if required for the current GPU partition (cluster-specific policy)