docs: public static void changeSign(DMatrixD1 input , DMatrixD1 output)
      {
          output.reshape(input.numRows,input.numCols);
  
          final int size = input.getNumElements();
  
          for( int i = 0; i < size; i++ ) {
              output.data[i] = -input.data[i];
          }
      }