Numerical representation

[Jon Herman]

It really is exactly the same process, but sure. Below is my Matlab
translation of the python code I posted earlier, it functions at the
increased accuracy I've shown above.

   k(:,1)=feval(deq, ti, x, mu);

     for n = 2:1:13
            nn=n-1;
            Xtemp1 = 0.0;
            for j = 1:1:nn
                Xtemp1 = Xtemp1 + beta(n,j) * k(:,j);
            end
            x=xwrk+ dt * Xtemp1;
            ti=twrk+alph(n)*dt;
            k(:,n)=feval(deq, ti, x, mu);
     end

      Xtemp2=0.0;
        for l  = 1:1:13
            Xtemp2=Xtemp2+ch(l)*k(:,l);
        end


        x=xwrk + dt * Xtemp2;
        t=twrk+dt;




On Mon, Mar 7, 2011 at 1:50 PM, Chris Rebert <clp2 at rebertia.com> wrote:

> >>> 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
> --
> Please avoid top-posting:
> http://en.wikipedia.org/wiki/Top-posting
>
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