Fix no-op os.system() call in be_func_parallel and be_func_parallel_u: OMP_NUM_THREADS must be set via os.environ in the parent process before Pool creation for forked workers to inherit it

Author: Lea Northcote

src/quemb/molbe/be_parallel.py

@@ -469,7 +469,7 @@ def be_func_parallel(
         the error norm, error vector, and the computed energy.
     """
     # Set the number of OpenMP threads
-    os.system("export OMP_NUM_THREADS=" + str(ompnum))
+    os.environ["OMP_NUM_THREADS"] = str(ompnum)
     nprocs = nproc // ompnum
 
     # Update the effective Hamiltonian with potentials
@@ -601,7 +601,7 @@ def be_func_parallel_u(
         Returns the computed energy
     """
     # Set the number of OpenMP threads
-    os.system("export OMP_NUM_THREADS=" + str(ompnum))
+    os.environ["OMP_NUM_THREADS"] = str(ompnum)
     nprocs = nproc // ompnum
 
     with Pool(nprocs) as pool_: