Index: src/test/org/apache/hama/TestDenseMatrix.java =================================================================== --- src/test/org/apache/hama/TestDenseMatrix.java (revision 775792) +++ src/test/org/apache/hama/TestDenseMatrix.java (working copy) @@ -178,6 +178,15 @@ assertEquals(result.get(i, j), m1.get(i, j) + m2.get(i, j)); } } + + Matrix subtract = result.add(-1.0, m2); + + for (int i = 0; i < SIZE; i++) { + for (int j = 0; j < SIZE; j++) { + double gap = (subtract.get(i, j) - m1.get(i, j)); + assertTrue(-0.00001 < gap && gap < 0.00001); + } + } } public void testMultiMatrixAdd() throws IOException {