Thanks all for the input, the remark about printing intermediate steps was a
very good one (and so obvious I can't believe it took me this long to get
there...)
The error was in my loop where I multiply by the "b" or "beta" coefficients.
The range for this loop (marked by j) is set up properly in
On 3/7/11 2:52 PM, Jon Herman wrote:
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;
The main choices for arbitrary point precision seem to be mpmath (which is
pure python) and GMP (C++ but with python wrapper; GMP is heavily used in
academia)
Links:
http://code.google.com/p/mpmath/
http://gmpy.sourceforge.net/
Katie
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Thanks Terry! Of course, speed is not my main concern at this point and I'm
more worried about precision...would you have some input on this discussion?
:)
Jon
On Mon, Mar 7, 2011 at 2:35 PM, Terry Reedy wrote:
> On 3/7/2011 1:59 PM, Jon Herman wrote:
>
>> And for the sake of completeness, th
On 3/7/2011 1:59 PM, Jon Herman wrote:
And for the sake of completeness, the derivative function I am calling
from my integrator (this is the 3 body problem in astrodynamics):
def F(mu, X, ti):
r1= pow((pow(X[0]+mu,2)+pow(X[1],2)+pow(X[2],2)),0.5)
x0 = X[0]; x1 = X[1]; x2 = X[2]
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:
>>> On Fri, Mar 4, 2011 at 2:32 PM, Jon Herman 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
And for the sake of additional completeness (I'm sorry I didn't think of all
this in one go): my derivative function in Python produces results that
agree with MATLAB to order e-16 (machine precision), so the error is
definitely building up in my integrator.
On Mon, Mar 7, 2011 at 11:59 AM, Jon
And for the sake of completeness, the derivative function I am calling from
my integrator (this is the 3 body problem in astrodynamics):
def F(mu, X, ti):
r1= pow((pow(X[0]+mu,2)+pow(X[1],2)+pow(X[2],2)),0.5)
r2= pow((pow(X[0]+mu-1,2)+pow(X[1],2)+pow(X[2],2)),0.5)
Ax= X[0]+2*X[4]-(1-
Sorry Robert, I'd missed your post when I just made my last one. The output
I am getting in Python looks as follows:
array([ 9.91565050e-01, 1.55680112e-05, -1.53258602e-05,
-5.75847623e-05, -9.64290960e-03, -8.26333458e-08])
This is the final state vector, consisting of 6 states (p
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
Actually, I import numpy in my code for array creation...in the
documentation I did not manage to find anything that would solve this
precision problem I mentioned however. If you're familiar with it, would you
happen to know what capability of numpy might solve my problem?
On Fri, Mar 4, 2011 a
On 3/4/11 4:32 PM, Jon Herman wrote:
Hello all,
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
On 3/4/11 5:49 PM, Santoso Wijaya wrote:
Have you taken a look at numpy? [1] It was written for exactly this kind of
usage.
~/santa
[1] http://numpy.scipy.org/
While numpy does provide arrays much like MATLAB's, it won't help at all for the
precision issues the OP is encountering (and hones
Have you taken a look at numpy? [1] It was written for exactly this kind of
usage.
~/santa
[1] http://numpy.scipy.org/
On Fri, Mar 4, 2011 at 2:32 PM, Jon Herman wrote:
> Hello all,
>
> I am new to the Python language and writing a Runge-Kutta-Fellberg 7(8)
> integrator in Python, which requi
Hello all,
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 Matl
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