def setUp(self): """ This sets up the test case. """ def f(t, y): eps = 1.e-6 my = 1. / eps yd_0 = y[1] yd_1 = my * ((1. - y[0]**2) * y[1] - y[0]) return N.array([yd_0, yd_1]) def jac(t, y): eps = 1.e-6 my = 1. / eps J = N.zeros([2, 2]) J[0, 0] = 0. J[0, 1] = 1. J[1, 0] = my * (-2. * y[0] * y[1] - 1.) J[1, 1] = my * (1. - y[0]**2) return J def jac_sparse(t, y): eps = 1.e-6 my = 1. / eps J = N.zeros([2, 2]) J[0, 0] = 0. J[0, 1] = 1. J[1, 0] = my * (-2. * y[0] * y[1] - 1.) J[1, 1] = my * (1. - y[0]**2) return sp.csc_matrix(J) #Define an Assimulo problem y0 = [2.0, -0.6] #Initial conditions exp_mod = Explicit_Problem(f, y0) exp_mod_t0 = Explicit_Problem(f, y0, 1.0) exp_mod_sp = Explicit_Problem(f, y0) exp_mod.jac = jac exp_mod_sp.jac = jac_sparse self.mod = exp_mod #Define an explicit solver self.sim = LSODAR(exp_mod) #Create a LSODAR solve self.sim_sp = LSODAR(exp_mod_sp) #Sets the parameters self.sim.atol = 1e-6 #Default 1e-6 self.sim.rtol = 1e-6 #Default 1e-6 self.sim.usejac = False
def run_example(with_plots=True): r""" Example for the use of LSODAR method to solve Van der Pol's equation .. math:: \dot y_1 &= y_2 \\ \dot y_2 &= \mu ((1.-y_1^2) y_2-y_1) with :math:`\mu=\frac{1}{5} 10^3`. on return: - :dfn:`exp_mod` problem instance - :dfn:`exp_sim` solver instance """ #Define the rhs def f(t,y): eps = 1.e-6 my = 1./eps yd_0 = y[1] yd_1 = my*((1.-y[0]**2)*y[1]-y[0]) return N.array([yd_0,yd_1]) y0 = [2.0,-0.6] #Initial conditions #Define an Assimulo problem exp_mod = Explicit_Problem(f,y0, name = "LSODAR: Van der Pol's equation") #Define an explicit solver exp_sim = LSODAR(exp_mod) #Create a Radau5 solver #Sets the parameters exp_sim.atol = 1e-4 #Default 1e-6 exp_sim.rtol = 1e-4 #Default 1e-6 #Simulate t, y = exp_sim.simulate(2.) #Simulate 2 seconds #Plot if with_plots: import pylab as P P.plot(t,y[:,0], marker='o') P.title(exp_mod.name) P.ylabel("State: $y_1$") P.xlabel("Time") P.show() #Basic test x1 = y[:,0] assert N.abs(x1[-1]-1.706168035) < 1e-3 #For test purpose return exp_mod, exp_sim
def test_event_localizer(self): exp_mod = Extended_Problem() #Create the problem exp_sim = LSODAR(exp_mod) #Create the solver exp_sim.verbosity = 0 exp_sim.report_continuously = True #Simulate t, y = exp_sim.simulate( 10.0, 1000) #Simulate 10 seconds with 1000 communications points #Basic test nose.tools.assert_almost_equal(y[-1][0], 8.0) nose.tools.assert_almost_equal(y[-1][1], 3.0) nose.tools.assert_almost_equal(y[-1][2], 2.0)
def run_example(with_plots=True): r""" Example of the use of Euler's method for a differential equation with a discontinuity (state event) and the need for an event iteration. on return: - :dfn:`exp_mod` problem instance - :dfn:`exp_sim` solver instance """ #Create an instance of the problem exp_mod = Extended_Problem() #Create the problem exp_sim = LSODAR(exp_mod) #Create the solver exp_sim.verbosity = 0 exp_sim.continuous_output = True #Simulate t, y = exp_sim.simulate( 10.0, 100) #Simulate 10 seconds with 1000 communications points #Plot if with_plots: import pylab as P P.plot(t, y) P.title("Solution of a differential equation with discontinuities") P.ylabel('States') P.xlabel('Time') P.show() return exp_mod, exp_sim #Basic test nose.tools.assert_almost_equal(y[-1][0], 8.0) nose.tools.assert_almost_equal(y[-1][1], 3.0) nose.tools.assert_almost_equal(y[-1][2], 2.0)
def run_example(with_plots=True): """ Bouncing ball example to demonstrate LSODAR's discontinuity handling. Also a way to use :program:`problem.initialize` and :program:`problem.handle_result` in order to provide extra information is demonstrated. The governing differential equation is .. math:: \\dot y_1 &= y_2\\\\ \\dot y_2 &= -9.81 and the switching functions are .. math:: \\mathrm{event}_0 &= y_1 \\;\\;\\;\\text{ if } \\;\\;\\;\\mathrm{sw}_0 = 1\\\\ \\mathrm{event}_1 &= y_2 \\;\\;\\;\\text{ if }\\;\\;\\; \\mathrm{sw}_1 = 1 otherwise the events are deactivated by setting the respective value to something different from 0. The event handling sets :math:`y_1 = - 0.88 y_1` and :math:`\\mathrm{sw}_1 = 1` if the first event triggers and :math:`\\mathrm{sw}_1 = 0` if the second event triggers. """ #Create an instance of the problem exp_mod = Extended_Problem() #Create the problem exp_sim = LSODAR(exp_mod) #Create the solver exp_sim.atol = 1.e-8 exp_sim.report_continuously = True exp_sim.verbosity = 30 #Simulate t, y = exp_sim.simulate(10.0) #Simulate 10 seconds #Plot if with_plots: P.subplot(221) P.plot(t, y) P.title('LSODAR Bouncing ball (one step mode)') P.ylabel('States: $y$ and $\dot y$') P.subplot(223) P.plot(exp_sim.t_sol, exp_sim.h_sol) P.title('LSODAR step size plot') P.xlabel('Time') P.ylabel('Sepsize') P.subplot(224) P.plot(exp_sim.t_sol, exp_sim.nq_sol) P.title('LSODAR order plot') P.xlabel('Time') P.ylabel('Order') P.suptitle(exp_mod.name) P.show() return exp_mod, exp_sim
def _default_solver_instance(self): from assimulo.solvers import LSODAR return LSODAR(self._assimulo_problem)