nthread is max number of threads, and setting that on the examples to avoid using too many cores

Author: maureeungaro

examples/geant4_basic/b1/b1.yaml

@@ -1,6 +1,7 @@
 experiment: examples
 runno: 1
 n: 300
+nthreads: 12
 
 gparticle:
   - name: gamma

examples/geant4_basic/b2/b2.yaml

@@ -1,6 +1,7 @@
 experiment: examples
 runno: 1
 n: 1
+nthreads: 12
 
 gparticle:
   - name: e-

examples/meson.build

@@ -11,9 +11,6 @@ examples_map = {
     }
 }
 
-
-
-
 foreach branch : examples_map.keys()
     examples = examples_map[branch]
 

goptions/examples/define_options.cc

@@ -22,9 +22,11 @@ GOptions defineOptions() {
     goptions.defineOption(GVariable("runno", 1, "sets the run number"), help);
 
     // nthreads: 8
-    help = "If not set, use all available threads. 0: use all threads\n";
-    help += "Example: -nthreads=12\n";
-    goptions.defineOption(GVariable("nthreads", 0, "number of threads"), help);
+    help = "Maximum number of threads to use.\n";
+	help += "If the number of cores available ncores is less then nthreads, use ncores instead.\n";
+    help += "If not set, use all available threads. 0: use all threads\n";
+    help += "Example: -nthreads=12  : . \n";
+    goptions.defineOption(GVariable("nthreads", 0, "maximum number of threads to use"), help);
 
     vector <GVariable> gparticle = {
             {"name",         goptions::NODFLT, "particle name"},

utilities/gemcUtilities.cc

@@ -16,10 +16,10 @@ namespace gemc {
 int get_nthreads(const std::shared_ptr<GOptions>& gopts, const std::shared_ptr<GLogger>& log) {
 	int useThreads = gopts->getScalarInt("nthreads");
 
-	int allThreads = G4Threading::G4GetNumberOfCores();
-	if (useThreads == 0) useThreads = allThreads;
+	int ncores = G4Threading::G4GetNumberOfCores();
+	if (useThreads == 0 || useThreads > ncores) useThreads = ncores;
 
-	log->info(0, "Using ", useThreads, " threads out of ", allThreads, " available.");
+	log->info(0, "Using ", useThreads, " threads out of ", ncores, " available cores.");
 
 	return useThreads;
 }