diff --git a/lib/colvars/colvaratoms.cpp b/lib/colvars/colvaratoms.cpp
index 0d0a339a69..e8046a97d5 100644
--- a/lib/colvars/colvaratoms.cpp
+++ b/lib/colvars/colvaratoms.cpp
@@ -367,6 +367,7 @@ int cvm::atom_group::parse(std::string const &conf)
         cvm::error("Error: atomsColValue, if provided, must be non-zero.\n", INPUT_ERROR);
       }
 
+      // NOTE: calls to add_atom() and/or add_atom_id() are in the proxy-implemented function
       cvm::load_atoms(atoms_file_name.c_str(), *this, atoms_col, atoms_col_value);
     }
   }
@@ -403,11 +404,21 @@ int cvm::atom_group::parse(std::string const &conf)
     }
   }
 
+  // We need to know the fitting options to decide whether the group is scalable
+  parse_error |= parse_fitting_options(group_conf);
+
+  if (is_available(f_ag_scalable_com) && !b_rotate) {
+    enable(f_ag_scalable_com);
+    enable(f_ag_scalable);
+  }
+
   if (is_enabled(f_ag_scalable) && !b_dummy) {
+    cvm::log("Enabling scalable calculation for group \""+this->key+"\".\n");
     index = (cvm::proxy)->init_atom_group(atoms_ids);
   }
 
-  parse_error |= parse_fitting_options(group_conf);
+  bool b_print_atom_ids = false;
+  get_keyval(group_conf, "printAtomIDs", b_print_atom_ids, false, colvarparse::parse_silent);
 
   // TODO move this to colvarparse object
   check_keywords(group_conf, key.c_str());
@@ -427,6 +438,10 @@ int cvm::atom_group::parse(std::string const &conf)
 	    cvm::to_str(total_mass)+", total charge = "+
             cvm::to_str(total_charge)+".\n");
 
+  if (b_print_atom_ids) {
+    cvm::log("Internal definition of the atom group:\n");
+  }
+
   cvm::decrease_depth();
 
   return (cvm::get_error() ? COLVARS_ERROR : COLVARS_OK);
@@ -583,6 +598,21 @@ int cvm::atom_group::add_atom_name_residue_range(std::string const &psf_segid,
 }
 
 
+std::string const cvm::atom_group::print_atom_ids() const
+{
+  size_t line_count = 0;
+  std::ostringstream os("");
+  for (size_t i = 0; i < atoms_ids.size(); i++) {
+    os << " " << std::setw(9) << atoms_ids[i];
+    if (++line_count == 7) {
+      os << "\n";
+      line_count = 0;
+    }
+  }
+  return os.str();
+}
+
+
 int cvm::atom_group::parse_fitting_options(std::string const &group_conf)
 {
   bool b_defined_center = get_keyval(group_conf, "centerReference", b_center, false);
@@ -1118,8 +1148,7 @@ void cvm::atom_group::apply_colvar_force(cvm::real const &force)
     log("Communicating a colvar force from atom group to the MD engine.\n");
   }
 
-  if (b_dummy)
-    return;
+  if (b_dummy) return;
 
   if (noforce) {
     cvm::error("Error: sending a force to a group that has "
@@ -1161,17 +1190,21 @@ void cvm::atom_group::apply_colvar_force(cvm::real const &force)
 
 void cvm::atom_group::apply_force(cvm::rvector const &force)
 {
-  if (b_dummy)
-    return;
+  if (cvm::debug()) {
+    log("Communicating a colvar force from atom group to the MD engine.\n");
+  }
+
+  if (b_dummy) return;
 
   if (noforce) {
     cvm::error("Error: sending a force to a group that has "
-               "\"disableForces\" defined.\n");
+               "\"enableForces\" set to off.\n");
     return;
   }
 
   if (is_enabled(f_ag_scalable)) {
     (cvm::proxy)->apply_atom_group_force(index, force);
+    return;
   }
 
   if (b_rotate) {
diff --git a/lib/colvars/colvaratoms.h b/lib/colvars/colvaratoms.h
index 7a4d031daa..a2a771a8a3 100644
--- a/lib/colvars/colvaratoms.h
+++ b/lib/colvars/colvaratoms.h
@@ -253,6 +253,8 @@ public:
     return atoms.size();
   }
 
+  std::string const print_atom_ids() const;
+
   /// \brief If this option is on, this group merely acts as a wrapper
   /// for a fixed position; any calls to atoms within or to
   /// functions that return disaggregated data will fail
diff --git a/lib/colvars/colvarcomp.cpp b/lib/colvars/colvarcomp.cpp
index 73b1dbd81c..050e03f78e 100644
--- a/lib/colvars/colvarcomp.cpp
+++ b/lib/colvars/colvarcomp.cpp
@@ -84,15 +84,12 @@ cvm::atom_group *colvar::cvc::parse_group(std::string const &conf,
       if (is_available(f_cvc_scalable_com) && is_available(f_cvc_com_based)) {
         enable(f_cvc_scalable_com);
         enable(f_cvc_scalable);
-        group->enable(f_ag_scalable_com);
-        group->enable(f_ag_scalable);
+        // The CVC makes the feature available;
+        // the atom group will enable it unless it needs to compute a rotational fit
+        group->provide(f_ag_scalable_com);
       }
 
       // TODO check for other types of parallelism here
-
-      if (is_enabled(f_cvc_scalable)) {
-        cvm::log("Will enable scalable calculation for group \""+group->key+"\".\n");
-      }
     }
 
     if (group->parse(conf) == COLVARS_OK) {
diff --git a/lib/colvars/colvardeps.cpp b/lib/colvars/colvardeps.cpp
index 7736ea14bd..a44f86c292 100644
--- a/lib/colvars/colvardeps.cpp
+++ b/lib/colvars/colvardeps.cpp
@@ -449,8 +449,10 @@ void colvardeps::init_ag_requires() {
 
   // Features that are implemented (or not) by all atom groups
   feature_states[f_ag_active]->available = true;
-  feature_states[f_ag_scalable_com]->available = (cvm::proxy->scalable_group_coms() == COLVARS_OK);
-  feature_states[f_ag_scalable]->available = feature_states[f_ag_scalable_com]->available;
+  // f_ag_scalable_com is provided by the CVC iff it is COM-based
+  feature_states[f_ag_scalable_com]->available = false;
+  // TODO make f_ag_scalable depend on f_ag_scalable_com (or something else)
+  feature_states[f_ag_scalable]->available = true;
 }
 
 
diff --git a/lib/colvars/colvarmodule.cpp b/lib/colvars/colvarmodule.cpp
index ee5db06e30..bd9548a748 100644
--- a/lib/colvars/colvarmodule.cpp
+++ b/lib/colvars/colvarmodule.cpp
@@ -810,6 +810,7 @@ int colvarmodule::analyze()
 
 int colvarmodule::setup()
 {
+  if (this->size() == 0) return cvm::get_error();
   // loop over all components of all colvars to reset masses of all groups
   for (std::vector<colvar *>::iterator cvi = colvars.begin();
        cvi != colvars.end();  cvi++) {
@@ -867,25 +868,35 @@ int colvarmodule::reset()
 
 int colvarmodule::setup_input()
 {
-  // name of input state file
-  restart_in_name = proxy->input_prefix().size() ?
-    std::string(proxy->input_prefix()+".colvars.state") :
-    std::string("") ;
+  if (this->size() == 0) return cvm::get_error();
+
+  std::string restart_in_name("");
 
   // read the restart configuration, if available
-  if (restart_in_name.size()) {
+  if (proxy->input_prefix().size()) {
     // read the restart file
+    restart_in_name = proxy->input_prefix();
     std::ifstream input_is(restart_in_name.c_str());
     if (!input_is.good()) {
-      cvm::error("Error: in opening restart file \""+
+      // try by adding the suffix
+      input_is.clear();
+      restart_in_name = restart_in_name+std::string(".colvars.state");
+      input_is.open(restart_in_name.c_str());
+    }
+
+    if (!input_is.good()) {
+      cvm::error("Error: in opening input file \""+
                  std::string(restart_in_name)+"\".\n",
                  FILE_ERROR);
       return COLVARS_ERROR;
     } else {
+      cvm::log(cvm::line_marker);
       cvm::log("Restarting from file \""+restart_in_name+"\".\n");
       read_restart(input_is);
       if (cvm::get_error() != COLVARS_OK) {
         return COLVARS_ERROR;
+      } else {
+        proxy->input_prefix().clear();
       }
       cvm::log(cvm::line_marker);
     }
@@ -897,7 +908,9 @@ int colvarmodule::setup_input()
 
 int colvarmodule::setup_output()
 {
-  int error_code = 0;
+  if (this->size() == 0) return cvm::get_error();
+
+  int error_code = COLVARS_OK;
 
   // output state file (restart)
   restart_out_name = proxy->restart_output_prefix().size() ?
@@ -1545,11 +1558,7 @@ std::list<std::string> colvarmodule::index_group_names;
 std::list<std::vector<int> > colvarmodule::index_groups;
 bool     colvarmodule::use_scripted_forces = false;
 bool     colvarmodule::scripting_after_biases = true;
-
-// file name prefixes
 std::string colvarmodule::output_prefix = "";
-std::string colvarmodule::restart_in_name = "";
-
 
 // i/o constants
 size_t const colvarmodule::it_width = 12;
diff --git a/lib/colvars/colvarmodule.h b/lib/colvars/colvarmodule.h
index 0b19d1f779..c8df6c7b5e 100644
--- a/lib/colvars/colvarmodule.h
+++ b/lib/colvars/colvarmodule.h
@@ -4,7 +4,7 @@
 #define COLVARMODULE_H
 
 #ifndef COLVARS_VERSION
-#define COLVARS_VERSION "2016-10-05"
+#define COLVARS_VERSION "2016-10-21"
 #endif
 
 #ifndef COLVARS_DEBUG
@@ -12,6 +12,9 @@
 #endif
 
 /*! \mainpage Main page
+This is the Developer's documentation for the Collective Variables Module.
+
+You can browse the class hierarchy or the list of source files.
  */
 
 /// \file colvarmodule.h
@@ -154,9 +157,6 @@ public:
   /// Prefix for all output files for this run
   static std::string output_prefix;
 
-  /// input restart file name (determined from input_prefix)
-  static std::string restart_in_name;
-
 
   /// Array of collective variables
   static std::vector<colvar *>     colvars;
@@ -197,6 +197,11 @@ public:
     return COLVARS_DEBUG;
   }
 
+  /// \brief How many objects are configured yet?
+  inline size_t const size() const
+  {
+    return colvars.size() + biases.size();
+  }
 
   /// \brief Constructor \param config_name Configuration file name
   /// \param restart_name (optional) Restart file name
diff --git a/lib/colvars/colvarparse.cpp b/lib/colvars/colvarparse.cpp
index e222fa9ecf..86cd00ad29 100644
--- a/lib/colvars/colvarparse.cpp
+++ b/lib/colvars/colvarparse.cpp
@@ -644,9 +644,9 @@ bool colvarparse::key_lookup(std::string const &conf,
 
       // find the matching closing brace
 
-      if (cvm::debug()) {
-        cvm::log("Multi-line value, config is now \""+line+"\".\n");
-      }
+//       if (cvm::debug()) {
+//         cvm::log("Multi-line value, config is now \""+line+"\".\n");
+//       }
 
       int brace_count = 1;
 
@@ -689,9 +689,9 @@ bool colvarparse::key_lookup(std::string const &conf,
             line_end = nl;
           line.append(conf, line_begin, (line_end-line_begin));
 
-          if (cvm::debug()) {
-            cvm::log("Added a new line, config is now \""+line+"\".\n");
-          }
+//           if (cvm::debug()) {
+//             cvm::log("Added a new line, config is now \""+line+"\".\n");
+//           }
         }
 
         if (brace_count < 0) {
diff --git a/lib/colvars/colvarproxy.h b/lib/colvars/colvarproxy.h
index 3d41cb58a7..0a0f550767 100644
--- a/lib/colvars/colvarproxy.h
+++ b/lib/colvars/colvarproxy.h
@@ -80,7 +80,7 @@ public:
   /// configuration)
   std::string input_prefix_str, output_prefix_str, restart_output_prefix_str;
 
-  inline std::string input_prefix()
+  inline std::string & input_prefix()
   {
     return input_prefix_str;
   }
diff --git a/lib/colvars/colvarscript.cpp b/lib/colvars/colvarscript.cpp
index a43907b07d..a0269aa7a9 100644
--- a/lib/colvars/colvarscript.cpp
+++ b/lib/colvars/colvarscript.cpp
@@ -155,7 +155,7 @@ int colvarscript::run(int argc, char const *argv[]) {
       result = "Missing arguments\n" + help_string();
       return COLVARSCRIPT_ERROR;
     }
-    proxy->input_prefix_str = argv[2];
+    proxy->input_prefix() = argv[2];
     if (colvars->setup_input() == COLVARS_OK) {
       return COLVARS_OK;
     } else {