Am 06.11.15 um 23:01 schrieb Abhishek:
I have code that runs perfectly well in MATLAB (using ode15s or
ode23s) but falters with Scipy odeint. The MATLAB code is for a
specific case of the generalized Python code. Here I have tried to
reproduce the specific case in Python. The logic in the code is
airtight and the algorithm is sound. I have also specified small rtol
and atol values, as well as a large mxstep.
My code is below:
[...Python code...]
Why am I getting a "stiff-looking" graph in Python
What does "stiff-looking" mean? I only know stiff differential
equations, but this leads to noisy results. Your plots are smooth.
(http://i.stack.imgur.com/UGWSH.png), when MATLAB gives me a proper
one (http://i.stack.imgur.com/F2jzd.jpg)? I would like to understand
where the problem lies and how to solve it.
It is very hard to analyze such a problem, unless you also post the
Matlab code and plot both solutions into a single graph.
What I can see at first is that the initial conditions can't be the
same. Your Python graph starts around 10^7, while the Matlab graph
starts at 10^5. WHat happens if you integrate a simpler system - say
does it make sense to set some of the coefficients to zero and if you
still get the same difference, can you simplify the program to expose
the problem? How do you know that the Matlab code produces the correct
answer?
Christian
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