diff --git a/trunk/paradiseo-mo/src/neighborhood/moNeighborhoodSizeUtils.h b/trunk/paradiseo-mo/src/neighborhood/moNeighborhoodSizeUtils.h
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+++ b/trunk/paradiseo-mo/src/neighborhood/moNeighborhoodSizeUtils.h
@@ -0,0 +1,66 @@
+/*
+  <moNeighborhoodSizeUtils.h>
+  Copyright (C) DOLPHIN Project-Team, INRIA Lille - Nord Europe, 2006-2010
+
+  Karima Boufaras, Thé Van LUONG
+
+  This software is governed by the CeCILL license under French law and
+  abiding by the rules of distribution of free software.  You can  use,
+  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".
+
+  As a counterpart to the access to the source code and  rights to copy,
+  modify and redistribute granted by the license, users are provided only
+  with a limited warranty  and the software's author,  the holder of the
+  economic rights,  and the successive licensors  have only  limited liability.
+
+  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 _moNeighborhoodSizeUtils_h
+#define _moNeighborhoodSizeUtils_h
+
+/**
+ * @return the factorial of an integer
+ * @param _i an integer
+ */
+
+static int factorial(int _i) {
+	if (_i == 0)
+		return 1;
+	else
+		return _i * factorial(_i - 1);
+}
+
+/**
+ * @return the neighborhood Size from the solution size and the exchange distance
+ * @param _n the solution size
+ * @param _xChange the number of positions to change
+ */
+
+static int sizeMapping(int _n, unsigned int _xChange) {
+	int _sizeMapping = _n;
+	for (int i = _xChange-1; i > 0; i--) {
+		_sizeMapping *= (_n - i);
+	}
+	_sizeMapping /= factorial(_xChange);
+	return _sizeMapping;
+}
+
+
+#endif