UPDATE_IF

Add a UPDATE_IF keyword. This keyword start a block
that is conditionally updated depending on the value
of its ARGuments.

Closes #38

src/core/PlumedMain.cpp

@@ -79,7 +79,6 @@ PlumedMain::PlumedMain():
   log.setLinePrefix("PLUMED: ");
   stopwatch.start();
   stopwatch.pause();
-  updateFlags.push(true);
   word_map["setBox"]=SETBOX;
   word_map["setPositions"]=SETPOSITIONS;
   word_map["setMasses"]=SETMASSES;
@@ -697,11 +696,14 @@ void PlumedMain::justApply(){
 
   if(detailedTimers) stopwatch.start("5C Update");
 // update step (for statistics, etc)
+  updateFlags.push(true);
   for(ActionSet::iterator p=actionSet.begin();p!=actionSet.end();++p){
     (*p)->beforeUpdate();
     if((*p)->isActive() && (*p)->checkUpdate() && updateFlagsTop()) (*p)->update();
   }
+  while(!updateFlags.empty()) updateFlags.pop();
   if(detailedTimers) stopwatch.stop("5C Update");
+  if(!updateFlags.empty()) plumed_merror("non matching changes in the update flags");
 // Check that no action has told the calculation to stop
   if(stopNow){
      if(stopFlag) (*stopFlag)=1;

src/generic/UpdateIf.cpp

+/* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+   Copyright (c) 2011-2015 The plumed team
+   (see the PEOPLE file at the root of the distribution for a list of names)
+
+   See http://www.plumed-code.org for more information.
+
+   This file is part of plumed, version 2.
+
+   plumed is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   plumed is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with plumed.  If not, see <http://www.gnu.org/licenses/>.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
+#include "core/ActionPilot.h"
+#include "core/ActionWithArguments.h"
+#include "core/ActionRegister.h"
+#include "core/PlumedMain.h"
+
+using namespace std;
+
+namespace PLMD{
+namespace generic{
+
+//+PLUMEDOC ANALYSIS UPDATE_IF
+/*
+Conditional update of other actions.
+
+
+This action can be used to enable and disable the update step for the following actions
+depending on the value of its arguments. This allows for example to extract snapshots
+with value of some CVs in a given range.
+
+When called with MORE_THAN and/or LESS_THAN keywords, this action starts an if block.
+The block is executed if all the arguments are less than all the respective values
+in the LESS_THAN keyword (if present) and all the arguments are more than all the
+respective values
+in the MORE_THAN keyword (if present).
+
+When called with the END flag, this action ends the corresponding IF block.
+Notice that in this case one should also provide the ARG keyword. It is recommended to
+use the same ARG keyword that was used to begin the block, so as to make the input more readable.
+
+Of course, blocks can be nested at will.
+
+There are many potential usages for this keyword. One might e.g. decide to analyze some variable
+only when another variable is within a given range.
+
+\warning
+Notice that not all the possible usage make
+particular sense. For example, conditionally updating a \ref METAD keyword
+(that is: adding hills only if a variable is within a given range)
+can lead to unexpected results.
+
+\par Examples
+The following input instructs plumed dump all the snapshots where an atom is in touch with
+the solute.
+\verbatim
+solute: GROUP ATOMS=1-124
+coord: COORDINATION GROUPA=solute GROUPB=500 R_0=0.5
+
+UPDATE_IF ARG=coord LESS_THAN=0.5
+DUMPATOMS ATOMS=solute,500 FILE=output.xyz
+UPDATE_IF ARG=coord END
+\endverbatim
+(See also \ref GROUP, \ref COORDINATION, and \ref DUMPATOMS)
+
+*/
+//+ENDPLUMEDOC
+
+class UpdateIf:
+public ActionPilot,
+public ActionWithArguments
+{
+  std::vector<double> lower;
+  std::vector<double> upper;
+  bool on;
+  bool end;
+public:
+  void prepare();
+  void calculate();
+  void beforeUpdate();
+  explicit UpdateIf(const ActionOptions&);
+  static void registerKeywords(Keywords& keys);
+  void apply(){}
+  ~UpdateIf();
+};
+
+PLUMED_REGISTER_ACTION(UpdateIf,"UPDATE_IF")
+
+void UpdateIf::registerKeywords(Keywords& keys){
+  Action::registerKeywords(keys);
+  ActionPilot::registerKeywords(keys);
+  ActionWithArguments::registerKeywords(keys);
+  keys.use("ARG");
+  keys.add("compulsory","STRIDE","1","the frequency with which the quantities of interest should be output");
+  keys.addFlag("END",false,"end");
+  keys.add("optional","LESS_THAN","upper bound");
+  keys.add("optional","MORE_THAN","lower bound");
+}
+
+UpdateIf::UpdateIf(const ActionOptions&ao):
+Action(ao),
+ActionPilot(ao),
+ActionWithArguments(ao),
+on(false),
+end(false)
+{
+  parseFlag("END",end);
+  parseVector("LESS_THAN",upper);
+  parseVector("MORE_THAN",lower);
+  if(end && upper.size()!=0) error("END and LESS_THAN are not compatible");
+  if(end && lower.size()!=0) error("END and MORE_THAN are not compatible");
+  if(upper.size()==0) upper.assign(getNumberOfArguments(),+std::numeric_limits<double>::max());
+  if(lower.size()==0) lower.assign(getNumberOfArguments(),-std::numeric_limits<double>::max());
+  if(upper.size()!=getNumberOfArguments()) error("LESS_THAN should have the same size as ARG");
+  if(lower.size()!=getNumberOfArguments()) error("MORE_THAN should have the same size as ARG");
+  for(unsigned i=0;i<getNumberOfArguments();++i){
+    log<<"  boundaries for argument "<<i<<"    "<<lower[i]<<" "<<upper[i]<<"\n";
+  }
+  checkRead();
+}
+
+void UpdateIf::prepare(){
+  on=false;
+}
+
+void UpdateIf::calculate(){
+  on=true;
+  for(unsigned i=0;i<getNumberOfArguments();++i){
+    if(getArgument(i)>=upper[i] || getArgument(i)<=lower[i]) on=false;
+  }
+}
+
+void UpdateIf::beforeUpdate(){
+  if(end) plumed.updateFlagsPop();
+  else {
+    if(on) plumed.updateFlagsPush(plumed.updateFlagsTop());
+    else   plumed.updateFlagsPush(false);
+  }
+}
+
+
+UpdateIf::~UpdateIf(){
+}
+
+}
+
+
+}