Source code for assimulo.examples.cvode_with_parameters

#!/usr/bin/env python 
# -*- coding: utf-8 -*-

# Copyright (C) 2010 Modelon AB
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, version 3 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

import numpy as N
import pylab as P
import nose
from assimulo.solvers import CVode
from assimulo.problem import Explicit_Problem

[docs]def run_example(with_plots=True): r""" This is the same example from the Sundials package (cvsRoberts_FSA_dns.c) Its purpose is to demonstrate the use of parameters in the differential equation. This simple example problem for CVode, due to Robertson see http://www.dm.uniba.it/~testset/problems/rober.php, is from chemical kinetics, and consists of the system: .. math:: \dot y_1 &= -p_1 y_1 + p_2 y_2 y_3 \\ \dot y_2 &= p_1 y_1 - p_2 y_2 y_3 - p_3 y_2^2 \\ \dot y_3 &= p_3 y_ 2^2 on return: - :dfn:`exp_mod` problem instance - :dfn:`exp_sim` solver instance """ def f(t, y, p): yd_0 = -p[0]*y[0]+p[1]*y[1]*y[2] yd_1 = p[0]*y[0]-p[1]*y[1]*y[2]-p[2]*y[1]**2 yd_2 = p[2]*y[1]**2 return N.array([yd_0,yd_1,yd_2]) #The initial conditions y0 = [1.0,0.0,0.0] #Initial conditions for y #Create an Assimulo explicit problem exp_mod = Explicit_Problem(f,y0, name='Robertson Chemical Kinetics Example') #Sets the options to the problem exp_mod.p0 = [0.040, 1.0e4, 3.0e7] #Initial conditions for parameters exp_mod.pbar = [0.040, 1.0e4, 3.0e7] #Create an Assimulo explicit solver (CVode) exp_sim = CVode(exp_mod) #Sets the solver paramters exp_sim.iter = 'Newton' exp_sim.discr = 'BDF' exp_sim.rtol = 1.e-4 exp_sim.atol = N.array([1.0e-8, 1.0e-14, 1.0e-6]) exp_sim.sensmethod = 'SIMULTANEOUS' #Defines the sensitvity method used exp_sim.suppress_sens = False #Dont suppress the sensitivity variables in the error test. exp_sim.report_continuously = True #Simulate t, y = exp_sim.simulate(4,400) #Simulate 4 seconds with 400 communication points #Basic test nose.tools.assert_almost_equal(y[-1][0], 9.05518032e-01, 4) nose.tools.assert_almost_equal(y[-1][1], 2.24046805e-05, 4) nose.tools.assert_almost_equal(y[-1][2], 9.44595637e-02, 4) nose.tools.assert_almost_equal(exp_sim.p_sol[0][-1][0], -1.8761, 2) #Values taken from the example in Sundials nose.tools.assert_almost_equal(exp_sim.p_sol[1][-1][0], 2.9614e-06, 8) nose.tools.assert_almost_equal(exp_sim.p_sol[2][-1][0], -4.9334e-10, 12) #Plot if with_plots: P.plot(t, y) P.title(exp_mod.name) P.xlabel('Time') P.ylabel('State') P.show() return exp_mod, exp_sim
if __name__=='__main__': mod,sim = run_example()