==================================================================================================== FAILURES =====================================================================================================_________________________________________________________________________________________ test_maxiter_worsening[lgmres] __________________________________________________________________________________________[gw1] linux -- Python 3.10.9 /var/tmp/portage/dev-python/scipy-1.10.0/work/scipy-1.10.0-python3_10/install/usr/bin/python3.10

solver = <function lgmres at 0x3fae312950>

    @pytest.mark.parametrize("solver", [
        pytest.param(gmres, marks=pytest.mark.xfail(platform.machine() == 'aarch64'
                                                    and sys.version_info[1] == 9,
                                                    reason="gh-13019")),
        qmr,
        pytest.param(lgmres, marks=pytest.mark.xfail(platform.machine() == 'ppc64le',
                                                     reason="fails on ppc64le")),
        pytest.param(cgs, marks=pytest.mark.xfail),
        pytest.param(bicg, marks=pytest.mark.xfail),
        pytest.param(bicgstab, marks=pytest.mark.xfail),
        pytest.param(gcrotmk, marks=pytest.mark.xfail),
        pytest.param(tfqmr, marks=pytest.mark.xfail)])
    def test_maxiter_worsening(solver):
        # Check error does not grow (boundlessly) with increasing maxiter.
        # This can occur due to the solvers hitting close to breakdown,
        # which they should detect and halt as necessary.
        # cf. gh-9100

        # Singular matrix, rhs numerically not in range
        A = np.array([[-0.1112795288033378, 0, 0, 0.16127952880333685],
                      [0, -0.13627952880333782+6.283185307179586j, 0, 0],
                      [0, 0, -0.13627952880333782-6.283185307179586j, 0],
                      [0.1112795288033368, 0j, 0j, -0.16127952880333785]])
        v = np.ones(4)
        best_error = np.inf
        tol = 7 if platform.machine() == 'aarch64' else 5

        for maxiter in range(1, 20):
            x, info = solver(A, v, maxiter=maxiter, tol=1e-8, atol=0)

            if info == 0:
                assert_(np.linalg.norm(A.dot(x) - v) <= 1e-8*np.linalg.norm(v))

            error = np.linalg.norm(A.dot(x) - v)
            best_error = min(best_error, error)

            # Check with slack
>           assert_(error <= tol*best_error)
E           AssertionError
A          = array([[-0.11127953+0.j        ,  0.        +0.j        ,
         0.        +0.j        ,  0.16127953+0.j        ],
       [ 0.        +0.j        , -0.13627953+6.28318531j,
         0.        +0.j        ,  0.        +0.j        ],
       [ 0.        +0.j        ,  0.        +0.j        ,
        -0.13627953-6.28318531j,  0.        +0.j        ],
       [ 0.11127953+0.j        ,  0.        +0.j        ,
         0.        +0.j        , -0.16127953+0.j        ]])
best_error = 1.414213562373095
error      = 67.94531422934396
info       = 8
maxiter    = 8
solver     = <function lgmres at 0x3fae312950>
tol        = 5
v          = array([1., 1., 1., 1.])
x          = array([-1.17813344e+15+0.j        , -6.61429022e+00-3.99819143j,
       -6.61429022e+00+3.99819143j, -8.12887631e+14+0.j        ])

../work/scipy-1.10.0-python3_10/install/usr/lib/python3.10/site-packages/scipy/sparse/linalg/_isolve/tests/test_iterative.py:487: AssertionError