Document openblas_set_num_threads_local(). See #4425

Author: nh2

cblas.h

@@ -40,6 +40,8 @@ extern "C" {
 /*Set the number of threads on runtime.*/
 void openblas_set_num_threads(int num_threads);
 void goto_set_num_threads(int num_threads);
+// "Local" means this number is used when OpenBLAS notices that
+// it is already in an OpenMP parallel region (`omp_in_parallel()`).
 int openblas_set_num_threads_local(int num_threads);
 
 /*Get the number of threads on runtime.*/

driver/others/blas_server_omp.c

@@ -69,7 +69,7 @@
 
 int blas_server_avail = 0;
 int blas_omp_number_max = 0;
-int blas_omp_threads_local = 1;
+int blas_omp_threads_local = 1; // num threads to use when already inside omp_in_parallel()
 int blas_is_num_threads_set_explicitly = 0; // tracks whether the user called openblas_set_num_threads()
 
 extern int openblas_omp_adaptive_env(void);