From 93cd0215bd28e20df3c044db4036780839528b4e Mon Sep 17 00:00:00 2001
From: edoapra <edoardo.apra@gmail.com>
Date: Tue, 3 Mar 2026 16:33:47 -0800
Subject: [PATCH] use hwloc to get no. hw cores to set max threads

---
 src/util/util_maxthreads.F | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/util/util_maxthreads.F b/src/util/util_maxthreads.F
index da3bd90d56..79fa804084 100644
--- a/src/util/util_maxthreads.F
+++ b/src/util/util_maxthreads.F
@@ -1,17 +1,30 @@
       subroutine util_setmaxthreads()
+c
+c     sets the number of openmp threads as
+c     number of hw cores / no. of process per node
+c
       implicit none
 #include "global.fh"
 #include "stdio.fh"
       integer ncpus,util_getncpus,max_thr,ppn
-      external util_getncpus
+      character*255 env_out
+      integer err8
 c
-      ncpus=util_getncpus()
-      if(ncpus.ne.0) then
-         call util_getppn(ppn)
-         max_thr=ncpus/ppn
-         if(ga_nodeid().eq.0)write(luout,*) ' ### ncpus max_thr',
-     N        ncpus,max_thr
-         call omp_set_num_threads(max_thr)
+c     skip if OMP_NUM_THREADS is set
+c
+      call get_environment_variable(
+     A     "OMP_NUM_THREADS", value=env_out, status=err8)
+      if(err8.ne.0) then
+         ncpus=util_getncpus()
+         if(ncpus.ne.0) then
+            call util_getppn(ppn)
+            max_thr=ncpus/ppn
+            if(ga_nodeid().eq.0)write(luout,97)
+     N           ncpus,max_thr
+            call omp_set_num_threads(max_thr)
+         endif
       endif
+ 97   format(2x,'NWChem w/ OpenMP: # of HW cores   = ',i4,
+     F     /2x,'NWChem w/ OpenMP: nprocs/node     = ',i4)
       return
       end