unit test for _common_den()

Benjamin Greiner · Benjamin Greiner · commit d26d6395288d · 2019-11-27T18:00:35.000+01:00
diff --git a/control/tests/xferfcn_test.py b/control/tests/xferfcn_test.py
@@ -496,8 +496,57 @@ def test_freqresp_mimo(self):
         np.testing.assert_array_equal(omega, true_omega)
 
     # Tests for TransferFunction.pole and TransferFunction.zero.
-    
-    @unittest.skipIf(not slycot_check(), "slycot not installed")
+
+    def test_common_den(self):
+        """ Test the helper function to compute common denomitators."""
+
+        # _common_den() computes the common denominator per input/column.
+        # The testing columns are:
+        # 0: no common poles
+        # 1: regular common poles
+        # 2: poles with multiplicity,
+        # 3: complex poles
+        # 4: complex poles below threshold
+
+        eps = np.finfo(float).eps
+        tol_imag = np.sqrt(eps*5*2*2)*0.9
+
+        numin = [[[1.], [1.], [1.], [1.], [1.]],
+                 [[1.], [1.], [1.], [1.], [1.]]]
+        denin = [[[1., 3., 2.],          # 0: poles: [-1, -2]
+                  [1., 6., 11., 6.],     # 1: poles: [-1, -2, -3]
+                  [1., 6., 11., 6.],     # 2: poles: [-1, -2, -3]
+                  [1., 6., 11., 6.],     # 3: poles: [-1, -2, -3]
+                  [1., 6., 11., 6.]],    # 4: poles: [-1, -2, -3],
+                 [[1., 12., 47., 60.],   # 0: poles: [-3, -4, -5]
+                  [1., 9., 26., 24.],    # 1: poles: [-2, -3, -4]
+                  [1., 7., 16., 12.],    # 2: poles: [-2, -2, -3]
+                  [1., 7., 17., 15.],    # 3: poles: [-2+1J, -2-1J, -3],
+                  np.poly([-2 + tol_imag * 1J, -2 - tol_imag * 1J, -3])]]
+        numref = np.array([
+                [[0.,  0.,  1., 12., 47., 60.],
+                 [0.,  0.,  0.,  1.,  4.,  0.],
+                 [0.,  0.,  0.,  1.,  2.,  0.],
+                 [0.,  0.,  0.,  1.,  4.,  5.],
+                 [0.,  0.,  0.,  1.,  2.,  0.]],
+                [[0.,  0.,  0.,  1.,  3.,  2.],
+                 [0.,  0.,  0.,  1.,  1.,  0.],
+                 [0.,  0.,  0.,  1.,  1.,  0.],
+                 [0.,  0.,  0.,  1.,  3.,  2.],
+                 [0.,  0.,  0.,  1.,  1.,  0.]]])
+        denref = np.array(
+                [[1., 15., 85., 225., 274., 120.],
+                 [1., 10., 35., 50., 24.,  0.],
+                 [1.,  8., 23., 28., 12.,  0.],
+                 [1., 10., 40., 80., 79., 30.],
+                 [1.,  8., 23., 28., 12.,  0.]])
+        sys = TransferFunction(numin, denin)
+        num, den, denorder = sys._common_den()
+        np.testing.assert_array_almost_equal(num[:2, :, :], numref)
+        np.testing.assert_array_almost_equal(num[2:, :, :],
+                                             np.zeros((3, 5, 6)))
+        np.testing.assert_array_almost_equal(den, denref)
+
     def test_pole_mimo(self):
         """Test for correct MIMO poles."""
 
@@ -508,13 +557,12 @@ def test_pole_mimo(self):
 
         np.testing.assert_array_almost_equal(p, [-2., -2., -7., -3., -2.])
 
-    @unittest.skipIf(not slycot_check(), "slycot not installed")
     def test_double_cancelling_poles_siso(self):
-        
+
         H = TransferFunction([1, 1], [1, 2, 1])
         p = H.pole()
         np.testing.assert_array_almost_equal(p, [-1, -1])
-    
+
     # Tests for TransferFunction.feedback
     def test_feedback_siso(self):
         """Test for correct SISO transfer function feedback."""
