ivps.three_body_restricted_first_order TypeError: second_to_first_order_auto ?

[denis-bz]

Hi Nicholas
have I done something stupid here ?

import sys
import numpy as np
from diffeqzoo import ivps, backend, __version__ as zooversion

if not backend.has_been_selected:  # 2nd run in ipython
    backend.select( "numpy" )
np.set_printoptions( edgeitems=10, threshold=10, linewidth=120, formatter=dict(
        float = lambda x: "%.2g" % x ))
print( 80 * "▄" )
print( "diffeqzoo", zooversion ) 

moonmass = 0.012277471
    # to change these params, run this.py  a=1  b=2,None  'c = expr' ... in sh or ipython --
for arg in sys.argv[1:]:
    exec( arg )
print( "moonmass = %g" % moonmass )
    
    # $site/ode/diffeqzoo/ivps/_nbody.py
f, u0, t_span, f_args = ivps.three_body_restricted_first_order( moonmass )
# TypeError: second_to_first_order_auto.<locals>.ivp_fn_transformed() takes 0 positional arguments b
    
print( f( u0 ))

What I'm really looking for is largish problems non-chaos, non-stiff, for which Δt oscillates a lot. Any suggestions ?
Thanks,
cheers
-- denis

[pnkraemer]

Hi! Sorry for the late reply, and thanks for reaching out!

The function ivps.three_body_restricted_first_order takes keyword arguments only, so the corresponding line above should read f, u0, t_span, f_args = ivps.three_body_restricted_first_order(standardised_moon_mass=moonmass). Does that help?

As for your second question, my usual go-to for high-dimensional ODE is a discretised PDE. Maybe a discretised wave equation since you don't want stiffness?