python - scipy ode update set_f_params inside function set as set_solout -


when integrating ode scipy, ode accepts function more arguments t , y. example:

def fun(t, y, param1, param2):

and value of these arguments can set using set_f_params method.

however, when using set_solout method , trying update params set_f_params inside function, integration remains same if params not being modified.

how modify the params using sol_out? i benefit dopri5 dense output, need non-homogeneous terms updated @ every time step.

a minimal example shown below.

import numpy np import matplotlib.pyplot plt scipy.integrate import ode  def fun(t, x, param):     return x - param  def f_param(t):     return t  ode1 = ode(fun).set_integrator('dopri5').set_initial_value([10.0]) ode1.set_f_params(f_param(0)) results1 = ([], [])  ode2 = ode(fun).set_integrator('dopri5').set_initial_value([10.0]) ode2.set_f_params(f_param(0)) results2 = ([], [])  def callback1(t, x):     results1[0].append(t)     results1[1].append(x.copy())  def callback2(t, x):     results2[0].append(t)     results2[1].append(x.copy())     ode2.set_f_params(f_param(t))  ode1.set_solout(callback1) ode2.set_solout(callback2)  ode1.integrate(3) ode2.integrate(3)  plt.plot(results1[0], results1[1], 'o-', alpha=0.7, label='ode1') plt.plot(results2[0], results2[1], '.--', label='ode2') plt.legend()

and results shown here:

image

this how 1 the new ode solvers released in scipy 1.0:

from functools import partial  import numpy np scipy.integrate import solve_ivp  import matplotlib.pyplot plt   def fun_fixed(t, x, param):     return x - param  sol_fixed = solve_ivp(     partial(fun_fixed, param=0), (0, 3), [10.0], dense_output=true)  def fun_param(t, x, fun):     return -x + fun(t)  def f_param(t):     return t  sol_param = solve_ivp(     partial(fun_param, fun=f_param), (0, 3), [10.0], dense_output=true)  t = np.linspace(0, 3, num=16)  plt.figure(figsize=(8, 5)) plt.plot(t, sol_fixed.sol(t)[0], 'o-', alpha=0.7, label='ode1') plt.plot(t, sol_param.sol(t)[0], 's-.', label='ode3') plt.legend()

two solutions


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