pyode-user

[Pyode-user] effect of start time on ode physics

[chris <dra...@gm...>]

Hi,

I have been doing some experiments as part of my phd and, tho the
theory predicts some differences in physics results, it was still
surprising to see it in actuality. the following differ only in the
start time (the second has a start time of 8000), but the final
resting place of the RH block is quite different from its position
when running the first example, even tho the spatial positions, size
of everything, duration of sim and grav constant are the same.

http://www.planet-earth.org/pyode/preciseBlocks.py
http://www.planet-earth.org/pyode/preciseBlocksTime8000.py

Can anyone explain to me what is happening inside ode to produce these
different results? I can explain the results abstractly, but not in
detailed terms relating to the specifics of pyode.

thanks,

chris

Re: [Pyode-user] effect of start time on ode physics

[chris <dra...@gm...>]

Hi list,

We have discussed the effect of position on simulation accuracy in
pyode but no one has answered this riddle about the start time, anyone
have an answer?

regards,

chris


On 11/24/06, chris <dra...@gm...> wrote:
> Hi,
>
> I have been doing some experiments as part of my phd and, tho the
> theory predicts some differences in physics results, it was still
> surprising to see it in actuality. the following differ only in the
> start time (the second has a start time of 8000), but the final
> resting place of the RH block is quite different from its position
> when running the first example, even tho the spatial positions, size
> of everything, duration of sim and grav constant are the same.
>
> http://www.planet-earth.org/pyode/preciseBlocks.py
> http://www.planet-earth.org/pyode/preciseBlocksTime8000.py
>
> Can anyone explain to me what is happening inside ode to produce these
> different results? I can explain the results abstractly, but not in
> detailed terms relating to the specifics of pyode.
>
> thanks,
>
> chris
>

Re: [Pyode-user] effect of start time on ode physics

[Timothy S. <tim...@gm...>]

In preciseBlocksTime8000.py, counter still starts from 0. To make the
two simulations equivalent, it should start at 7980.

--
Timothy

Re: [Pyode-user] effect of start time on ode physics

[chris <dra...@gm...>]

Ah, I did not explain properly: the dropping of the right hand block
starts at counter=8000 in the file preciseBlocksTime8000.py. I.e. it
just starts dropping at a later time but otherwise the simulation is
the same (position of objects, gravity etc) and, one would expect, end
up in the same rest state as for the
http://www.planet-earth.org/pyode/preciseBlocks.py where the right
hand block is dropped when counter = 20.

cheers,

chris

On 11/26/06, Timothy Stranex <tim...@gm...> wrote:
> In preciseBlocksTime8000.py, counter still starts from 0. To make the
> two simulations equivalent, it should start at 7980.
>
> --
> Timothy
>
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