Make SMP parallelism for Colvars optional

lib/colvars/colvarmodule.cpp

@@ -156,6 +156,12 @@ int colvarmodule::parse_global_params(std::string const &conf)
     read_index_file(index_file_name.c_str());
   }
 
+  if (parse->get_keyval(conf, "smp", proxy->b_smp_active, proxy->b_smp_active)) {
+    if (proxy->b_smp_active == false) {
+      cvm::log("SMP parallelism has been disabled.\n");
+    }
+  }
+
   parse->get_keyval(conf, "analysis", b_analysis, b_analysis);
 
   parse->get_keyval(conf, "debugGradientsStepSize", debug_gradients_step_size,

lib/colvars/colvarproxy.h

@@ -25,7 +25,7 @@ public:
   colvarmodule *colvars;
 
   /// Default constructor
-  inline colvarproxy() : script(NULL) {}
+  inline colvarproxy() : script(NULL), b_smp_active(true) {}
 
   /// Default destructor
   virtual ~colvarproxy() {}
@@ -116,12 +116,15 @@ public:
 
   // ***************** SHARED-MEMORY PARALLELIZATION *****************
 
-  /// Whether or not threaded parallelization is available
+  /// Whether threaded parallelization is available (TODO: make this a cvm::deps feature)
   virtual int smp_enabled()
   {
     return COLVARS_NOT_IMPLEMENTED;
   }
 
+  /// Whether threaded parallelization should be used (TODO: make this a cvm::deps feature)
+  bool b_smp_active;
+
   /// Distribute calculation of colvars (and their components) across threads
   virtual int smp_colvars_loop()
   {

src/USER-COLVARS/colvarproxy_lammps.cpp

@@ -333,7 +333,10 @@ int colvarproxy_lammps::backup_file(char const *filename)
 
 int colvarproxy_lammps::smp_enabled()
 {
-  return COLVARS_OK;
+  if (b_smp_active) {
+    return COLVARS_OK;
+  }
+  return COLVARS_ERROR;
 }