On Thu, Oct 30, 2014 at 9:52 AM, <[email protected]> wrote:
> #In The Name of God#
> Hello to every one. I need to solve a large system of first order ODE's:(i
> is imaginary unit)
> i*y'[t]=A[t].y[t]
> to find PSI[t](a vector of n functions of t), given PSI[0]and A[t] (a sparse
> matrix with linear terms of t as non-zero elements).
> As a begginer Sage user, I tried to follow instructions in "Solving ODE
> numerically by GSL" entry in Sage Documentation; for a small instance of my
> system my code is as follows:
>
> var('s','t','T')
> A=matrix(A_elements_dict);
NameError: name 'A_elements_dict' is not defined
>
> f=A(s=t/T)
>
> reset('i');
> reset('x');
>
> def Sch(t,y):
> return [ -i*sum(f[j,k]*y[j] for k in range(2^L)) for j in range(2^L)]
>
> NL1=[1 for i in range(2^L)];
>
> TS=ode_solver()
> TS.algorithm = "rk4"
> TS.function=Sch
> TS.y_0 = NL1
> TS.ode_solve(t_span=[0,T], num_points=100)
> print TS.solution;
>
> But this error raised:
>
> File "/tmp/tmpwWuHMa/___code___.py", line 128, in <module>
> TS.ode_solve(t_span=[_sage_const_0 ,T], num_points=_sage_const_100 )
> File "ode.pyx", line 539, in sage.gsl.ode.ode_solver.ode_solve
> (build/cythonized/sage/gsl/ode.c:5053)
> ValueError: error solving
>
>
> However,since this syntax results in (trivial) answer when I set A[t]=0, I
> interpret that it means my code is correct (without syntax errors or loss of
> predefinitions).
> Can anyone help me to find out the bug?
> As I stated before, I am still a begginer in Sage.
>
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--
William Stein
Professor of Mathematics
University of Washington
http://wstein.org
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