Python linalg.expm_cond函数代码示例

 def test_univariate(self):
     np.random.seed(12345)
     for x in np.linspace(-5, 5, num=11):
         A = np.array([[x]])
         assert_allclose(expm_cond(A), abs(x))
     for x in np.logspace(-2, 2, num=11):
         A = np.array([[x]])
         assert_allclose(expm_cond(A), abs(x))
     for i in range(10):
         A = np.random.randn(1, 1)
         assert_allclose(expm_cond(A), np.absolute(A)[0, 0])

    def test_expm_cond_fuzz(self):
        np.random.seed(12345)
        eps = 1e-5
        nsamples = 10
        for i in range(nsamples):
            n = np.random.randint(2, 5)
            A = np.random.randn(n, n)
            A_norm = scipy.linalg.norm(A)
            X = expm(A)
            X_norm = scipy.linalg.norm(X)
            kappa = expm_cond(A)

            # Look for the small perturbation that gives the greatest
            # relative error.
            f = functools.partial(_help_expm_cond_search, A, A_norm, X, X_norm, eps)
            guess = np.ones(n * n)
            out = minimize(f, guess, method="L-BFGS-B")
            xopt = out.x
            yopt = f(xopt)
            p_best = eps * _normalized_like(np.reshape(xopt, A.shape), A)
            p_best_relerr = _relative_error(expm, A, p_best)
            assert_allclose(p_best_relerr, -yopt * eps)

            # Check that the identified perturbation indeed gives greater
            # relative error than random perturbations with similar norms.
            for j in range(5):
                p_rand = eps * _normalized_like(np.random.randn(*A.shape), A)
                assert_allclose(norm(p_best), norm(p_rand))
                p_rand_relerr = _relative_error(expm, A, p_rand)
                assert_array_less(p_rand_relerr, p_best_relerr)

            # The greatest relative error should not be much greater than
            # eps times the condition number kappa.
            # In the limit as eps approaches zero it should never be greater.
            assert_array_less(p_best_relerr, (1 + 2 * eps) * eps * kappa)

 def test_expm_bad_condition_number(self):
     A = np.array([
         [-1.128679820, 9.614183771e4, -4.524855739e9, 2.924969411e14],
         [0, -1.201010529, 9.634696872e4, -4.681048289e9],
         [0, 0, -1.132893222, 9.532491830e4],
         [0, 0, 0, -1.179475332],
         ])
     kappa = expm_cond(A)
     assert_array_less(1e36, kappa)

 def test_expm_cond_smoke(self):
     np.random.seed(1234)
     for n in range(1, 4):
         A = np.random.randn(n, n)
         kappa = expm_cond(A)
         assert_array_less(0, kappa)