[SciPy-User] lsoda vs. Coulomb friction

Charles R Harris charlesr.harris@gmail....
Wed Feb 3 19:44:46 CST 2010


On Wed, Feb 3, 2010 at 6:29 PM, Charles R Harris
<charlesr.harris@gmail.com>wrote:

>
>
> On Wed, Feb 3, 2010 at 6:05 PM, Anne Archibald <peridot.faceted@gmail.com>wrote:
>
>> 2010/2/3 David Goldsmith <d.l.goldsmith@gmail.com>:
>>
>> > "   :
>> >     :
>> > Returns
>> >  -------
>> >     :
>> >     :
>> >  infodict : dict, only returned if full_output == True
>> >      Dictionary containing additional output information
>> >         :
>> >         :
>> >      'mused'  a vector of method indicators for each successful time
>> step:
>> >               1: adams (nonstiff), 2: bdf (stiff)"
>> >
>> > Note that it's a _return_ value: apparently with odeint, you can't
>> specify
>> > which method to use, you can only "hear" which method the algorithm
>> decided
>> > to use for you.
>>
>> In particular, odeint always (?) starts with a non-stiff method and
>> switches to a stiff method if the problem appears to warrant it. It
>> does not seem that odeint ever switches back to a non-stiff method
>> even if the problem enters a non-stiff region.
>>
>> In any case, I'm not sure there's any reason to think that a stiff
>> solver will help with the OP's problem,
>
>
> Me neither, what motivated that suggestion is that if the object "sticks",
> then the ODE becomes an algebraic equation. Another WAG would be to try a
> low order integrator. I'm rather curious to see what works best here.
>
>
Here is a bit of discussion <http://tinyurl.com/y8kxxyb>. The author says
that smoothing methods lead to stiff equations and notes that these are time
consuming.

Chuck
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