示例#1
0
    def test_parab_FD(self):

        model = Problem(impl=impl)
        root = model.root = Group()
        par = root.add('par', ParallelGroup())

        par.add('c1', Parab1D(root=2.0))
        par.add('c2', Parab1D(root=3.0))

        root.add('p1', ParamComp('x', val=0.0))
        root.add('p2', ParamComp('x', val=0.0))
        root.connect('p1.x', 'par.c1.x')
        root.connect('p2.x', 'par.c2.x')

        root.add('sumcomp', ExecComp('sum = x1+x2'))
        root.connect('par.c1.y', 'sumcomp.x1')
        root.connect('par.c2.y', 'sumcomp.x2')

        driver = model.driver = pyOptSparseDriver()
        driver.add_param('p1.x', low=-100, high=100)
        driver.add_param('p2.x', low=-100, high=100)
        driver.add_objective('sumcomp.sum')

        root.fd_options['force_fd'] = True

        model.setup(check=False)
        model.run()

        if not MPI or self.comm.rank == 0:
            assert_rel_error(self, model['p1.x'], 2.0, 1.e-6)
            assert_rel_error(self, model['p2.x'], 3.0, 1.e-6)
    def test_fd_options_meta_step_size(self):
        class MetaParaboloid(Component):
            """ Evaluates the equation f(x,y) = (x-3)^2 + xy + (y+4)^2 - 3 """
            def __init__(self):
                super(MetaParaboloid, self).__init__()

                # Params
                self.add_param('x', 1.0, fd_step_size=1.0e5)
                self.add_param('y', 1.0, fd_step_size=1.0e5)

                # Unknowns
                self.add_output('f_xy', 0.0)

            def solve_nonlinear(self, params, unknowns, resids):
                """f(x,y) = (x-3)^2 + xy + (y+4)^2 - 3
                Optimal solution (minimum): x = 6.6667; y = -7.3333
                """

                x = params['x']
                y = params['y']

                f_xy = ((x - 3.0)**2 + x * y + (y + 4.0)**2 - 3.0)
                unknowns['f_xy'] = f_xy

            def jacobian(self, params, unknowns, resids):
                """Analytical derivatives"""

                x = params['x']
                y = params['y']
                J = {}

                J['f_xy', 'x'] = (2.0 * x - 6.0 + y)
                J['f_xy', 'y'] = (2.0 * y + 8.0 + x)

                return J

        prob = Problem()
        prob.root = Group()
        comp = prob.root.add('comp', MetaParaboloid())
        prob.root.add('p1', ParamComp('x', 15.0))
        prob.root.add('p2', ParamComp('y', 15.0))
        prob.root.connect('p1.x', 'comp.x')
        prob.root.connect('p2.y', 'comp.y')

        comp.fd_options['force_fd'] = True

        prob.setup(check=False)
        prob.run()

        # Make sure bad meta step_size is used
        # Derivative should be way high with this.

        J = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')
        self.assertGreater(J['comp.f_xy']['p1.x'][0][0], 1000.0)
    def __init__(self):
        super(TestProb, self).__init__()

        self.root = root = Group()
        root.add('c1', SimpleArrayComp())
        root.add('p1', ParamComp('p', 1 * np.ones(2)))
        root.connect('p1.p', 'c1.x')

        root.add('ci1', SimpleImplicitComp())
        root.add('pi1', ParamComp('p', 1.))
        root.connect('pi1.p', 'ci1.x')
示例#4
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    def test_indices(self):
        size = 10

        root = Group()

        root.add('P1', ParamComp('x', np.zeros(size)))
        root.add(
            'C1',
            ExecComp('y = x * 2.',
                     y=np.zeros(size // 2),
                     x=np.zeros(size // 2)))
        root.add(
            'C2',
            ExecComp('y = x * 3.',
                     y=np.zeros(size // 2),
                     x=np.zeros(size // 2)))

        root.connect('P1.x', "C1.x", src_indices=list(range(size // 2)))
        root.connect('P1.x', "C2.x", src_indices=list(range(size // 2, size)))

        prob = Problem(root)
        prob.setup(check=False)

        root.P1.unknowns['x'][0:size // 2] += 1.0
        root.P1.unknowns['x'][size // 2:size] -= 1.0

        prob.run()

        assert_rel_error(self, root.C1.params['x'], np.ones(size // 2), 0.0001)
        assert_rel_error(self, root.C2.params['x'], -np.ones(size // 2),
                         0.0001)
示例#5
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    def test_simple_array_model2(self):
        prob = Problem()
        prob.root = Group()
        comp = prob.root.add(
            'comp',
            ExecComp('y = mat.dot(x)',
                     x=np.zeros((2, )),
                     y=np.zeros((2, )),
                     mat=np.array([[2., 7.], [5., -3.]])))

        p1 = prob.root.add('p1', ParamComp('x', np.ones([2])))

        prob.root.connect('p1.x', 'comp.x')

        prob.setup(check=False)
        prob.run()

        data = prob.check_partial_derivatives(out_stream=None)

        assert_rel_error(self, data['comp'][('y', 'x')]['abs error'][0], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['abs error'][1], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['abs error'][2], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['rel error'][0], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['rel error'][1], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['rel error'][2], 0.0,
                         1e-5)
示例#6
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    def test_simple_array_model(self):
        prob = Problem()
        prob.root = Group()
        prob.root.add(
            'comp',
            ExecComp(['y[0]=2.0*x[0]+7.0*x[1]', 'y[1]=5.0*x[0]-3.0*x[1]'],
                     x=np.zeros([2]),
                     y=np.zeros([2])))

        prob.root.add('p1', ParamComp('x', np.ones([2])))

        prob.root.connect('p1.x', 'comp.x')

        prob.setup(check=False)
        prob.run()

        data = prob.check_partial_derivatives(out_stream=None)

        assert_rel_error(self, data['comp'][('y', 'x')]['abs error'][0], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['abs error'][1], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['abs error'][2], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['rel error'][0], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['rel error'][1], 0.0,
                         1e-5)
        assert_rel_error(self, data['comp'][('y', 'x')]['rel error'][2], 0.0,
                         1e-5)
    def test_fd_options_form(self):

        prob = Problem()
        prob.root = Group()
        comp = prob.root.add('comp', Paraboloid())
        prob.root.add('p1', ParamComp('x', 15.0))
        prob.root.add('p2', ParamComp('y', 15.0))
        prob.root.connect('p1.x', 'comp.x')
        prob.root.connect('p2.y', 'comp.y')

        comp.fd_options['force_fd'] = True
        comp.fd_options['form'] = 'forward'

        param_list = ['p1.x']
        unknowns_list = ['comp.f_xy']
        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(param_list, unknowns_list, return_format='dict')
        assert_rel_error(self, J['comp.f_xy']['p1.x'][0][0], 39.0, 1e-6)

        # Make sure it gives good result with small stepsize
        comp.fd_options['form'] = 'backward'

        J = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')
        assert_rel_error(self, J['comp.f_xy']['p1.x'][0][0], 39.0, 1e-6)

        # Make sure it gives good result with small stepsize
        comp.fd_options['form'] = 'central'

        J = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')
        assert_rel_error(self, J['comp.f_xy']['p1.x'][0][0], 39.0, 1e-6)

        # Now, Make sure we really are going foward and backward
        comp.fd_options['form'] = 'forward'
        comp.fd_options['step_size'] = 1e3
        J = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')
        self.assertGreater(J['comp.f_xy']['p1.x'][0][0], 0.0)

        comp.fd_options['form'] = 'backward'
        J = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')
        self.assertLess(J['comp.f_xy']['p1.x'][0][0], 0.0)

        # Central should get pretty close even for the bad stepsize
        comp.fd_options['form'] = 'central'
        J = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')
        assert_rel_error(self, J['comp.f_xy']['p1.x'][0][0], 39.0, 1e-1)
    def test_linear_system(self):
        root = Group()

        root.add('lin', LinearSystem(3))

        x = np.array([1, 2, -3])
        A = np.array([[5.0, -3.0, 2.0], [1.0, 7.0, -4.0], [1.0, 0.0, 8.0]])
        b = A.dot(x)

        root.add('p1', ParamComp('A', A))
        root.add('p2', ParamComp('b', b))
        root.connect('p1.A', 'lin.A')
        root.connect('p2.b', 'lin.b')

        prob = Problem(root)
        prob.setup(check=False)
        prob.run()

        # Make sure it gets the right answer
        assert_rel_error(self, prob['lin.x'], x, .0001)
        assert_rel_error(self, np.linalg.norm(prob.root.resids.vec), 0.0,
                         1e-10)

        # Compare against calculated derivs
        Ainv = np.linalg.inv(A)
        dx_dA = np.outer(Ainv, -x).reshape(3, 9)
        dx_db = Ainv

        J = prob.calc_gradient(['p1.A', 'p2.b'], ['lin.x'],
                               mode='fwd',
                               return_format='dict')
        assert_rel_error(self, J['lin.x']['p1.A'], dx_dA, .0001)
        assert_rel_error(self, J['lin.x']['p2.b'], dx_db, .0001)

        J = prob.calc_gradient(['p1.A', 'p2.b'], ['lin.x'],
                               mode='rev',
                               return_format='dict')
        assert_rel_error(self, J['lin.x']['p1.A'], dx_dA, .0001)
        assert_rel_error(self, J['lin.x']['p2.b'], dx_db, .0001)

        J = prob.calc_gradient(['p1.A', 'p2.b'], ['lin.x'],
                               mode='fd',
                               return_format='dict')
        assert_rel_error(self, J['lin.x']['p1.A'], dx_dA, .0001)
        assert_rel_error(self, J['lin.x']['p2.b'], dx_db, .0001)
示例#9
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    def test_subarray_to_promoted_var(self):
        root = Group()

        P = root.add('P', ParamComp('x', np.array([1., 2., 3.])))
        G = root.add('G', Group())
        C = root.add('C', SimpleComp())

        A = G.add('A', SimpleArrayComp())  # , promotes=['x', 'y'])

        root.connect('P.x', 'G.A.x', src_indices=[0, 1])
        root.connect('P.x', 'C.x', src_indices=[
            2,
        ])

        prob = Problem(root)
        prob.setup(check=False)
        prob.run()

        assert_rel_error(self, root.G.A.params['x'], np.array([1., 2.]),
                         0.0001)
        self.assertAlmostEqual(root.C.params['x'], 3.)

        # no try the same thing with promoted var
        root = Group()

        P = root.add('P', ParamComp('x', np.array([1., 2., 3.])))
        G = root.add('G', Group())
        C = root.add('C', SimpleComp())

        A = G.add('A', SimpleArrayComp(), promotes=['x', 'y'])

        root.connect('P.x', 'G.x', src_indices=[0, 1])
        root.connect('P.x', 'C.x', src_indices=[
            2,
        ])

        prob = Problem(root)
        prob.setup(check=False)
        prob.run()

        assert_rel_error(self, root.G.A.params['x'], np.array([1., 2.]),
                         0.0001)
        self.assertAlmostEqual(root.C.params['x'], 3.)
示例#10
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    def test_simple_jac(self):
        group = Group()
        group.add('x_param', ParamComp('x', 1.0), promotes=['*'])
        group.add('mycomp', ExecComp(['y=2.0*x']), promotes=['x', 'y'])

        prob = Problem()
        prob.root = group
        prob.root.ln_solver = ExplicitSolver()
        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(['x'], ['y'], mode='fwd', return_format='dict')
        assert_rel_error(self, J['y']['x'][0][0], 2.0, 1e-6)

        J = prob.calc_gradient(['x'], ['y'], mode='rev', return_format='dict')
        assert_rel_error(self, J['y']['x'][0][0], 2.0, 1e-6)
示例#11
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    def test_simple_matvec_subbed(self):
        group = Group()
        group.add('mycomp', SimpleCompDerivMatVec(), promotes=['x', 'y'])

        prob = Problem()
        prob.root = Group()
        prob.root.add('x_param', ParamComp('x', 1.0), promotes=['*'])
        prob.root.add('sub', group, promotes=['*'])

        prob.root.ln_solver = ExplicitSolver()
        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(['x'], ['y'], mode='fwd', return_format='dict')
        assert_rel_error(self, J['y']['x'][0][0], 2.0, 1e-6)

        J = prob.calc_gradient(['x'], ['y'], mode='rev', return_format='dict')
        assert_rel_error(self, J['y']['x'][0][0], 2.0, 1e-6)
示例#12
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    def test_array2D(self):
        group = Group()
        group.add('x_param', ParamComp('x', np.ones((2, 2))), promotes=['*'])
        group.add('mycomp', ArrayComp2D(), promotes=['x', 'y'])

        prob = Problem()
        prob.root = group
        prob.root.ln_solver = ExplicitSolver()
        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(['x'], ['y'], mode='fwd', return_format='dict')
        Jbase = prob.root.mycomp._jacobian_cache
        diff = np.linalg.norm(J['y']['x'] - Jbase['y', 'x'])
        assert_rel_error(self, diff, 0.0, 1e-8)

        J = prob.calc_gradient(['x'], ['y'], mode='rev', return_format='dict')
        diff = np.linalg.norm(J['y']['x'] - Jbase['y', 'x'])
        assert_rel_error(self, diff, 0.0, 1e-8)
示例#13
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    def test_array_to_scalar(self):
        root = Group()

        root.add('P1', ParamComp('x', np.array([2., 3.])))
        root.add('C1', SimpleComp())
        root.add('C2', ExecComp('y = x * 3.', y=0., x=0.))

        root.connect('P1.x', 'C1.x', src_indices=[
            0,
        ])
        root.connect('P1.x', 'C2.x', src_indices=[
            1,
        ])

        prob = Problem(root)
        prob.setup(check=False)
        prob.run()

        self.assertAlmostEqual(root.C1.params['x'], 2.)
        self.assertAlmostEqual(root.C2.params['x'], 3.)
示例#14
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    def test_complex_step2(self):
        prob = Problem(Group())
        comp = prob.root.add('comp', ExecComp('y=x*x + x*2.0'))
        prob.root.add('p1', ParamComp('x', 2.0))
        prob.root.connect('p1.x', 'comp.x')

        comp.fd_options['force_fd'] = False

        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(['p1.x'], ['comp.y'],
                               mode='fwd',
                               return_format='dict')
        assert_rel_error(self, J['comp.y']['p1.x'], np.array([6.0]), 0.00001)

        J = prob.calc_gradient(['p1.x'], ['comp.y'],
                               mode='rev',
                               return_format='dict')
        assert_rel_error(self, J['comp.y']['p1.x'], np.array([6.0]), 0.00001)
示例#15
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    def test_prom_conns(self):
        # this test mimics some of the connections found in test_nozzle in pycycle. The bug was that
        # an unknown that was connected to one parameter
        # (desVars.Ps_exhaust to nozzle.press_calcs.Ps_exhaust), was not being connected to the
        # other parameters ('nozzle.ideal_flow.chem_eq.n2ls.P', 'nozzle.ideal_flow.mach_calc.Ps',
        # and 'nozzle.ideal_flow.props.tp2props.P') that were connected via input-input connections
        # to nozzle.press_calcs.Ps_exhaust.

        prob = Problem(root=Group())
        root = prob.root
        desVars = root.add("desVars",
                           ParamComp('Ps_exhaust', 1.0),
                           promotes=('Ps_exhaust', ))
        nozzle = root.add("nozzle", Group())
        press_calcs = nozzle.add('press_calcs',
                                 ExecComp('out=Ps_exhaust'),
                                 promotes=('Ps_exhaust', ))
        ideal_flow = nozzle.add("ideal_flow", Group())
        chem_eq = ideal_flow.add('chem_eq', Group(), promotes=('P', ))
        n2ls = chem_eq.add("n2ls", ExecComp('out=P'), promotes=('P', ))
        props = ideal_flow.add("props", Group(), promotes=('P', ))
        tp2props = props.add("tp2props", ExecComp('out=P'), promotes=('P', ))
        mach_calc = ideal_flow.add("mach_calc",
                                   ExecComp('out=Ps'),
                                   promotes=('Ps', ))

        nozzle.connect('Ps_exhaust', 'ideal_flow.Ps')
        root.connect('Ps_exhaust', 'nozzle.Ps_exhaust')
        ideal_flow.connect('Ps', 'P')

        prob.setup(check=False)

        expected_targets = set([
            'nozzle.ideal_flow.chem_eq.n2ls.P',
            'nozzle.press_calcs.Ps_exhaust', 'nozzle.ideal_flow.mach_calc.Ps',
            'nozzle.ideal_flow.props.tp2props.P'
        ])
        self.assertEqual(set(prob.root.connections), expected_targets)

        for tgt in expected_targets:
            self.assertTrue('desVars.Ps_exhaust' in prob.root.connections[tgt])
    def test_overrides(self):
        class OverrideComp(Component):
            def __init__(self):
                super(OverrideComp, self).__init__()

                # Params
                self.add_param('x', 3.0)

                # Unknowns
                self.add_output('y', 5.5)

            def solve_nonlinear(self, params, unknowns, resids):
                """ Doesn't do much. """
                unknowns['y'] = 7.0 * params['x']

            def apply_linear(self, params, unknowns, dparams, dunknowns,
                             dresids, mode):
                """Never Call."""
                raise RuntimeError(
                    "This should have been overridden by force_fd.")

            def jacobian(self, params, unknowns, resids):
                """Never Call."""
                raise RuntimeError(
                    "This should have been overridden by force_fd.")

        prob = Problem()
        prob.root = Group()
        comp = prob.root.add('comp', OverrideComp())
        prob.root.add('p1', ParamComp('x', 2.0))
        prob.root.connect('p1.x', 'comp.x')

        comp.fd_options['force_fd'] = True

        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(['p1.x'], ['comp.y'],
                               mode='fwd',
                               return_format='dict')
        assert_rel_error(self, J['comp.y']['p1.x'][0][0], 7.0, 1e-6)
    def test_no_derivatives(self):

        prob = Problem()
        prob.root = Group()
        comp = prob.root.add('comp', ExecComp('y=x*2.0'))
        prob.root.add('p1', ParamComp('x', 2.0))
        prob.root.connect('p1.x', 'comp.x')

        comp.fd_options['force_fd'] = True

        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(['p1.x'], ['comp.y'],
                               mode='fwd',
                               return_format='dict')
        assert_rel_error(self, J['comp.y']['p1.x'][0][0], 2.0, 1e-6)

        J = prob.calc_gradient(['p1.x'], ['comp.y'],
                               mode='rev',
                               return_format='dict')
        assert_rel_error(self, J['comp.y']['p1.x'][0][0], 2.0, 1e-6)
    def test_fd_options_step_size(self):

        prob = Problem()
        prob.root = Group()
        comp = prob.root.add('comp', Paraboloid())
        prob.root.add('p1', ParamComp([('x', 15.0), ('y', 15.0)]))
        prob.root.connect('p1.x', 'comp.x')
        prob.root.connect('p1.y', 'comp.y')

        comp.fd_options['force_fd'] = True

        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')
        assert_rel_error(self, J['comp.f_xy']['p1.x'][0][0], 39.0, 1e-6)

        # Make sure step_size is used
        # Derivative should be way high with this.
        comp.fd_options['step_size'] = 1e5

        J = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')
        self.assertGreater(J['comp.f_xy']['p1.x'][0][0], 1000.0)
示例#19
0
    def test_derivatives(self):
        meta = MetaModel()
        meta.add_param('x', 0.)
        meta.add_output('f', 0.)
        meta.default_surrogate = FloatKrigingSurrogate()

        prob = Problem(Group())
        prob.root.add('meta', meta, promotes=['x'])
        prob.root.add('p', ParamComp('x', 0.), promotes=['x'])
        prob.setup(check=False)

        prob['meta.train:x'] = [0., .25, .5, .75, 1.]
        prob['meta.train:f'] = [1., .75, .5, .25, 0.]
        prob['x'] = 0.125
        prob.run()

        stream = cStringIO()
        prob.check_partial_derivatives(out_stream=stream)

        abs_errors = findall('Absolute Error \(.+\) : (.+)', stream.getvalue())
        self.assertTrue(len(abs_errors) > 0)
        for match in abs_errors:
            abs_error = float(match)
            self.assertTrue(abs_error < 1e-6)
示例#20
0
    def __init__(self, root=1.0):
        super(MP_Point, self).__init__()

        self.add('p', ParamComp('x', val=0.0))
        self.add('c', Parab1D(root=root))
        self.connect('p.x', 'c.x')
    def test_fd_options_meta_form(self):
        class MetaParaboloid(Component):
            """ Evaluates the equation f(x,y) = (x-3)^2 + xy + (y+4)^2 - 3 """
            def __init__(self):
                super(MetaParaboloid, self).__init__()

                # Params
                self.add_param('x1', 1.0, fd_form='forward')
                self.add_param('x2', 1.0, fd_form='backward')
                self.add_param('y', 1.0)

                # Unknowns
                self.add_output('f_xy', 0.0)

            def solve_nonlinear(self, params, unknowns, resids):
                """f(x,y) = (x-3)^2 + xy + (y+4)^2 - 3
                Optimal solution (minimum): x = 6.6667; y = -7.3333
                """

                x1 = params['x1']
                x2 = params['x2']
                y = params['y']

                f_xy = ((x1 - 3.0)**2 + (x2 - 3.0)**2 + (x2 + x2) * y +
                        (y + 4.0)**2 - 3.0)
                unknowns['f_xy'] = f_xy

            def jacobian(self, params, unknowns, resids):
                """Analytical derivatives"""

                x1 = params['x1']
                x2 = params['x2']
                y = params['y']
                J = {}

                J['f_xy', 'x1'] = (2.0 * x1 - 6.0 + x2 * y)
                J['f_xy', 'x2'] = (2.0 * x2 - 6.0 + x1 * y)
                J['f_xy', 'y'] = (2.0 * y + 8.0 + x1 + x2)

                return J

        prob = Problem()
        prob.root = Group()
        comp = prob.root.add('comp', MetaParaboloid())
        prob.root.add('p11', ParamComp('x1', 15.0))
        prob.root.add('p12', ParamComp('x2', 15.0))
        prob.root.add('p2', ParamComp('y', 15.0))
        prob.root.connect('p11.x1', 'comp.x1')
        prob.root.connect('p12.x2', 'comp.x2')
        prob.root.connect('p2.y', 'comp.y')

        comp.fd_options['force_fd'] = True
        comp.fd_options['step_size'] = 1e3

        params_list = ['p11.x1']
        unknowns_list = ['comp.f_xy']

        prob.setup(check=False)
        prob.run()

        J = prob.calc_gradient(params_list,
                               unknowns_list,
                               return_format='dict')
        self.assertGreater(J['comp.f_xy']['p11.x1'][0][0], 0.0)

        J = prob.calc_gradient(['p12.x2'], unknowns_list, return_format='dict')
        self.assertLess(J['comp.f_xy']['p12.x2'][0][0], 0.0)
    def test_fd_options_step_type(self):
        class ScaledParaboloid(Component):
            """ Evaluates the equation f(x,y) = (x-3)^2 + xy + (y+4)^2 - 3 """
            def __init__(self):
                super(ScaledParaboloid, self).__init__()

                # Params
                self.add_param('x', 1.0)
                self.add_param('y', 1.0)

                # Unknowns
                self.add_output('f_xy', 0.0)

                self.scale = 1.0e-6

            def solve_nonlinear(self, params, unknowns, resids):
                """f(x,y) = (x-3)^2 + xy + (y+4)^2 - 3
                Optimal solution (minimum): x = 6.6667; y = -7.3333
                """

                x = params['x']
                y = params['y']

                f_xy = ((x - 3.0)**2 + x * y + (y + 4.0)**2 - 3.0)
                unknowns['f_xy'] = self.scale * f_xy

            def jacobian(self, params, unknowns, resids):
                """Analytical derivatives"""

                x = params['x']
                y = params['y']
                J = {}

                J['f_xy', 'x'] = (2.0 * x - 6.0 + y) * self.scale
                J['f_xy', 'y'] = (2.0 * y + 8.0 + x) * self.scale

                return J

        prob = Problem()
        prob.root = Group()
        comp = prob.root.add('comp', ScaledParaboloid())
        prob.root.add('p1', ParamComp('x', 8.0 * comp.scale))
        prob.root.add('p2', ParamComp('y', 8.0 * comp.scale))
        prob.root.connect('p1.x', 'comp.x')
        prob.root.connect('p2.y', 'comp.y')

        comp.fd_options['force_fd'] = True
        comp.fd_options['step_type'] = 'absolute'

        prob.setup(check=False)
        prob.run()

        J1 = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')

        comp.fd_options['step_type'] = 'relative'
        J2 = prob.calc_gradient(['p1.x'], ['comp.f_xy'], return_format='dict')

        # Couldnt put together a case where one is much worse, so just make sure they
        # are not equal.
        self.assertNotEqual(self, J1['comp.f_xy']['p1.x'][0][0],
                            J2['comp.f_xy']['p1.x'][0][0])