Add more efficient sym-Implementation

dune/microstructure/matrix_operations.hh

@@ -31,14 +31,31 @@ namespace MatrixOperations {
 	}
 	
 
+	// static MatrixRT sym (MatrixRT M) { // 1/2 (M^T + M)
+    // 	MatrixRT ret(0);
+    // 	for (int i = 0; i< 3; i++)
+    // 		for (int j = 0; j< 3; j++)
+    // 			ret[i][j] = 0.5 * (M[i][j] + M[j][i]);
+    // 	return ret;
+	// }
+
+
 	static MatrixRT sym (MatrixRT M) { // 1/2 (M^T + M)
     	MatrixRT ret(0);
-    	for (int i = 0; i< 3; i++)
-    		for (int j = 0; j< 3; j++)
-    			ret[i][j] = 0.5 * (M[i][j] + M[j][i]);
+    	for (int i=0; i<3; i++)
+		{
+			ret[i][i] = M[i][i];
+    		for (int j=i+1; j<3; j++)
+			{
+    			ret[i][j] = 0.5*(M[i][j] + M[j][i]);
+				ret[j][i] = ret[i][j];
+			}
+		}
     	return ret;
 	}
 
+
+
 	static VectorRT crossProduct (VectorRT v, VectorRT w) { // v otimes w
     	return {v[1]*w[2] - v[2]*w[1], -1*(v[0]*w[2] - v[2]*w[0]), v[0]*w[1] - v[1]*w[0]};
 	}