Numerical representation

[Chris Rebert]

>>> On Fri, Mar 4, 2011 at 2:32 PM, Jon Herman <jfc.herman at gmail.com> wrote:
>>>>
>>>> I am new to the Python language and writing a Runge-Kutta-Fellberg 7(8)
>>>> integrator in Python, which requires an extreme numerical precision for my
>>>> particular application. Unfortunately, I can not seem to attain it.
>>>> The interesting part is if I take my exact code and translate it to
>>>> Matlab code (so I use the exact same process and numbers), I get a far
>>>> superior precision (the one I am expecting, in fact). This leads me to think
>>>> I need to call a certain command in my Python script in order to make sure
>>>> no truncation errors are building up over my integration.
>>>>
>>>> Has anyone had similar problems? Is there a difference between how
>>>> Matlab and Python store numbers, and if so how do I make Python more
>>>> accurate?
>>>>
<snip>
On Mon, Mar 7, 2011 at 10:36 AM, Jon Herman <jfc.herman at gmail.com> wrote:
> I'm starting to run out of ideas of what to do...I've imported the true
> division (I'm using Python 2.7) to make sure I wasn't accidentally using any
> integers but the results remain identical, so it's not a division problem.
> I've copied the loop I'm running below, is there any mathematical operation
> I am making here that may have an accuracy problem? Thanks for any advice
> you can give!
>
<Python code snipped>

Since the problem is quite possibly due to an imperfection in the
translation process, I think also posting your MATLAB integrator code
for comparison would be advisable.

Cheers,
Chris
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