--- branches/development/src/math/SquareMatrix.hpp	2011/11/22 20:38:56	1665
+++ branches/development/src/math/SquareMatrix.hpp	2012/06/12 13:20:28	1753
@@ -135,7 +135,26 @@ namespace OpenMD {
 
       return tmp;
     }
+    
+    /**
+     * Returns the tensor contraction (double dot product) of two rank 2
+     * tensors (or Matrices)
+     * @param t1 first tensor
+     * @param t2 second tensor
+     * @return the tensor contraction (double dot product) of t1 and t2
+     */
+    Real doubleDot( const SquareMatrix<Real, Dim>& t1, const SquareMatrix<Real, Dim>& t2 ) {
+      Real tmp;
+      tmp = 0;
+      
+      for (unsigned int i = 0; i < Dim; i++)
+        for (unsigned int j =0; j < Dim; j++)
+          tmp += t1[i][j] * t2[i][j];
+      
+      return tmp;
+    }
 
+
     /** Tests if this matrix is symmetrix. */            
     bool isSymmetric() const {
       for (unsigned int i = 0; i < Dim - 1; i++)