diff --git a/trunk/paradiseo-mo/src/explorer/moSimpleHCexplorer.h b/trunk/paradiseo-mo/src/explorer/moSimpleHCexplorer.h
index 80cab3412..5ecba3318 100644
--- a/trunk/paradiseo-mo/src/explorer/moSimpleHCexplorer.h
+++ b/trunk/paradiseo-mo/src/explorer/moSimpleHCexplorer.h
@@ -143,8 +143,10 @@ public:
     virtual void move(EOT & _solution) {
         //move the solution
         (*best).move(_solution);
+
         //update its fitness
         _solution.fitness((*best).fitness());
+
     };
 
     /**
diff --git a/trunk/paradiseo-mo/src/mo.h b/trunk/paradiseo-mo/src/mo.h
index b81d5750a..470959f71 100755
--- a/trunk/paradiseo-mo/src/mo.h
+++ b/trunk/paradiseo-mo/src/mo.h
@@ -148,6 +148,8 @@
 #include <perturb/moSolInit.h>
 
 #include <problems/bitString/moBitNeighbor.h>
+#include <problems/bitString/moPopBitNeighbor.h>
+#include <problems/bitString/moPopSol.h>
 #include <problems/eval/moOneMaxIncrEval.h>
 #include <problems/permutation/moShiftNeighbor.h>
 #include <problems/permutation/moSwapNeighbor.h>
diff --git a/trunk/paradiseo-mo/src/problems/bitString/moBitNeighbor.h b/trunk/paradiseo-mo/src/problems/bitString/moBitNeighbor.h
index d942eb937..73e464fa4 100644
--- a/trunk/paradiseo-mo/src/problems/bitString/moBitNeighbor.h
+++ b/trunk/paradiseo-mo/src/problems/bitString/moBitNeighbor.h
@@ -57,6 +57,7 @@ public:
      */
     virtual void move(EOT & _solution) {
         _solution[key] = !_solution[key];
+        _solution.invalidate();
     }
 
     /**
diff --git a/trunk/paradiseo-mo/src/problems/bitString/moPopBitNeighbor.h b/trunk/paradiseo-mo/src/problems/bitString/moPopBitNeighbor.h
new file mode 100644
index 000000000..883ffa921
--- /dev/null
+++ b/trunk/paradiseo-mo/src/problems/bitString/moPopBitNeighbor.h
@@ -0,0 +1,119 @@
+/*
+<moPopBitNeighbor.h>
+Copyright (C) DOLPHIN Project-Team, INRIA Lille - Nord Europe, 2006-2010
+
+Sébastien Verel, Arnaud Liefooghe, Jérémie Humeau
+
+This software is governed by the CeCILL license under French law and
+abiding by the rules of distribution of free software.  You can  ue,
+modify and/ or redistribute the software under the terms of the CeCILL
+license as circulated by CEA, CNRS and INRIA at the following URL
+"http://www.cecill.info".
+
+In this respect, the user's attention is drawn to the risks associated
+with loading,  using,  modifying and/or developing or reproducing the
+software by the user in light of its specific status of free software,
+that may mean  that it is complicated to manipulate,  and  that  also
+therefore means  that it is reserved for developers  and  experienced
+professionals having in-depth computer knowledge. Users are therefore
+encouraged to load and test the software's suitability as regards their
+requirements in conditions enabling the security of their systems and/or
+data to be ensured and,  more generally, to use and operate it in the
+same conditions as regards security.
+The fact that you are presently reading this means that you have had
+knowledge of the CeCILL license and that you accept its terms.
+
+ParadisEO WebSite : http://paradiseo.gforge.inria.fr
+Contact: paradiseo-help@lists.gforge.inria.fr
+*/
+
+#ifndef _moPopBitNeighbor_h
+#define _moPopBitNeighbor_h
+
+#include <eoPop.h>
+#include <ga/eoBit.h>
+#include <problems/bitString/moPopSol.h>
+#include <neighborhood/moBackableNeighbor.h>
+#include <neighborhood/moIndexNeighbor.h>
+
+/**
+ * Neighbor related to a vector of Bit
+ */
+template< class Fitness >
+class moPopBitNeighbor : public moBackableNeighbor< moPopSol<eoBit<Fitness> > >, public moIndexNeighbor< moPopSol<eoBit<Fitness> > >
+{
+public:
+    typedef moPopSol<eoBit<Fitness> > EOT ;
+
+    using moBackableNeighbor<EOT>::fitness;
+    using moIndexNeighbor<EOT>::key;
+
+    /**
+     * move the solution
+     * @param _solution the solution to move
+     */
+    virtual void move(EOT & _solution) {
+    	if(_solution.size()>0){
+    		size=_solution[0].size();
+    		_solution[key/size][key%size] = !_solution[key/size][key%size];
+//    		fit=_solution[key/size].fitness();
+    		_solution[key/size].invalidate();
+//    		fitSol=_solution.fitness();
+            _solution.invalidate();
+    	}
+    }
+
+    /**
+     * move back the solution (useful for the evaluation by modif)
+     * @param _solution the solution to move back
+     */
+    virtual void moveBack(EOT & _solution) {
+        _solution[key/size][key%size] = !_solution[key/size][key%size];
+//        _solution[key/size].fitness(fit);
+    }
+
+    /**
+     * return the class name
+     * @return the class name as a std::string
+     */
+    virtual std::string className() const {
+        return "moPopBitNeighbor";
+    }
+
+    /**
+     * Read object.\
+     * Calls base class, just in case that one had something to do.
+     * The read and print methods should be compatible and have the same format.
+     * In principle, format is "plain": they just print a number
+     * @param _is a std::istream.
+     * @throw runtime_std::exception If a valid object can't be read.
+     */
+    virtual void readFrom(std::istream& _is) {
+        std::string fitness_str;
+        int pos = _is.tellg();
+        _is >> fitness_str;
+        if (fitness_str == "INVALID") {
+            throw std::runtime_error("invalid fitness");
+        }
+        else {
+            Fitness repFit ;
+            _is.seekg(pos);
+            _is >> repFit;
+            _is >> key;
+            fitness(repFit);
+        }
+    }
+
+    /**
+     * Write object. Called printOn since it prints the object _on_ a stream.
+     * @param _os A std::ostream.
+     */
+    virtual void printOn(std::ostream& _os) const {
+        _os << fitness() << ' ' << key << std::endl;
+    }
+
+private:
+    unsigned int size;
+};
+
+#endif
diff --git a/trunk/paradiseo-mo/src/problems/bitString/moPopSol.h b/trunk/paradiseo-mo/src/problems/bitString/moPopSol.h
new file mode 100644
index 000000000..9b6688a27
--- /dev/null
+++ b/trunk/paradiseo-mo/src/problems/bitString/moPopSol.h
@@ -0,0 +1,51 @@
+/*
+<moPopSol.h>
+Copyright (C) DOLPHIN Project-Team, INRIA Lille - Nord Europe, 2006-2010
+
+Sébastien Verel, Arnaud Liefooghe, Jérémie Humeau
+
+This software is governed by the CeCILL license under French law and
+abiding by the rules of distribution of free software.  You can  ue,
+modify and/ or redistribute the software under the terms of the CeCILL
+license as circulated by CEA, CNRS and INRIA at the following URL
+"http://www.cecill.info".
+
+In this respect, the user's attention is drawn to the risks associated
+with loading,  using,  modifying and/or developing or reproducing the
+software by the user in light of its specific status of free software,
+that may mean  that it is complicated to manipulate,  and  that  also
+therefore means  that it is reserved for developers  and  experienced
+professionals having in-depth computer knowledge. Users are therefore
+encouraged to load and test the software's suitability as regards their
+requirements in conditions enabling the security of their systems and/or
+data to be ensured and,  more generally, to use and operate it in the
+same conditions as regards security.
+The fact that you are presently reading this means that you have had
+knowledge of the CeCILL license and that you accept its terms.
+
+ParadisEO WebSite : http://paradiseo.gforge.inria.fr
+Contact: paradiseo-help@lists.gforge.inria.fr
+*/
+
+#ifndef _moPopSol_h
+#define _moPopSol_h
+
+#include <EO.h>
+#include <eoPop.h>
+
+template <class EOT>
+class moPopSol : public EO<double>, public eoPop<EOT>{
+public:
+	typedef typename EO<double>::Fitness Fitness;
+	using EO<double>::invalidate;
+
+	  virtual void printOn(std::ostream& _os) const
+	  {
+	        _os << (*this).size() << " " << (*this).fitness() << '\n';
+	        for(unsigned int i=0; i<(*this).size(); i++)
+	        	_os << (*this).operator[](i) << std::endl;
+	  }
+
+};
+
+#endif