reset number of threads to 1 when using no accelerator or opt

tools/lammps-gui/lammpsgui.cpp

@@ -508,6 +508,8 @@ void LammpsGui::update_variables()
 
     for (const auto &line : doc) {
 
+        if (line.isEmpty()) continue;
+
         // first find variable definitions.
         // index variables are special since they can be overridden from the command line
         auto index = indexvar.match(line);

tools/lammps-gui/preferences.cpp

@@ -40,8 +40,8 @@
 #include <QSpacerItem>
 #include <QSpinBox>
 #include <QTabWidget>
-#include <QVBoxLayout>
 #include <QThread>
+#include <QVBoxLayout>
 
 #if defined(_OPENMP)
 #include <omp.h>
@@ -110,10 +110,15 @@ void Preferences::accept()
         }
     }
 
-    // store number of threads
+    // store number of threads, reset to 1 for "None" and "Opt" settings
     QLineEdit *field = tabWidget->findChild<QLineEdit *>("nthreads");
-    if (field)
-        if (field->hasAcceptableInput()) settings->setValue("nthreads", field->text());
+    if (field) {
+        int accel = settings->value("accelerator", AcceleratorTab::None).toInt();
+        if ((accel == AcceleratorTab::None) || (accel == AcceleratorTab::Opt))
+            settings->setValue("nthreads", 1);
+        else if (field->hasAcceptableInput())
+            settings->setValue("nthreads", field->text());
+    }
 
     // store image width, height, zoom, and rendering settings