basic support for auxiliary label maps

can be created with labelmap via mapID keyword
referenced like mymapID::C
where C is an atom type, for example

src/atom.cpp

@@ -204,6 +204,7 @@ Atom::Atom(LAMMPS *lmp) : Pointers(lmp)
 
   // type labels
 
+  nlmap = 0;
   lmaps = nullptr;
 
   // custom atom arrays
@@ -1990,7 +1991,7 @@ void Atom::add_molecule_atom(Molecule *onemol, int iatom,
    allocate space for type label map
 ------------------------------------------------------------------------- */
 
-void Atom::add_label_map(std::string mapID)
+int Atom::add_label_map(std::string mapID)
 {
   labelmapflag = 1;
   lmaps = (LabelMap **)
@@ -2005,6 +2006,7 @@ void Atom::add_label_map(std::string mapID)
   lmaps[nlmap]->nimpropertypes = nimpropertypes;
   lmaps[nlmap]->allocate_type_labels();
   nlmap++;
+  return nlmap - 1;
 }
 
 /* ----------------------------------------------------------------------
@@ -2014,13 +2016,33 @@ void Atom::add_label_map(std::string mapID)
 
 int Atom::find_label(std::string label, int mode)
 {
-  // find label map ... in progress
+  int ilmap = 0;
-  int ilmap;
+
-  ilmap = 0;
+  // check for auxiliary map prefix
+
+  int pos = label.find("::");
+  if (pos != std::string::npos) {
+    ilmap = find_labelmap(label.substr(0,pos));
+    if (ilmap == -1) return -1;
+    label = label.substr(pos+2);
+  }
 
   return lmaps[ilmap]->find(label,mode);
 }
 
+/* ----------------------------------------------------------------------
+   find first label map in set with ID
+   return -1 if does not exist
+------------------------------------------------------------------------- */
+
+int Atom::find_labelmap(std::string id)
+{
+  int ilmap;
+  for (ilmap = 0; ilmap < nlmap; ilmap++)
+    if (id == lmaps[ilmap]->id) return ilmap;
+  return -1;
+}
+
 /* ----------------------------------------------------------------------
    reorder owned atoms so those in firstgroup appear first
    called by comm->exchange() if atom_modify first group is set

src/atom.h

@@ -329,8 +329,9 @@ class Atom : protected Pointers {
   int find_molecule(char *);
   void add_molecule_atom(class Molecule *, int, int, tagint);
 
-  void add_label_map(std::string mapID = "");
+  int add_label_map(std::string mapID = "");
   int find_label(std::string, int);
+  int find_labelmap(std::string);
 
   void first_reorder();
   virtual void sort();

src/input.cpp

@@ -1592,10 +1592,26 @@ void Input::kspace_style()
 
 void Input::labelmap()
 {
+  if (narg < 2 || (narg % 2 == 0)) error->all(FLERR,"Illegal labelmap command");
   if (domain->box_exist == 0)
     error->all(FLERR,"Labelmap command before simulation box is defined");
+
   if (!atom->labelmapflag) atom->add_label_map();
-  atom->lmaps[0]->modify_lmap(narg,arg);
+
+  int ilmap = 0;
+  std::string mapid;
+  for (int i = 1; i < narg; i++) {
+    if (strcmp(arg[i],"mapID") == 0) {
+      mapid = arg[i+1];
+      ilmap = atom->find_labelmap(mapid);
+      if (ilmap == -1) ilmap = atom->add_label_map(mapid);
+      if (narg > i+2) error->all(FLERR,"Illegal labelmap command");
+      narg = i - 2;
+      break;
+    }
+    i++;
+  }
+  atom->lmaps[ilmap]->modify_lmap(narg,arg);
 }
 
 /* ---------------------------------------------------------------------- */