On 08/16/2010 05:26 PM, Richard wrote:
> I'd already posted this problem on the sage-support mailing list, but
> the issue could not be resolved. As it appears to be a bug, I am
> cross-posting to this list.
>
> [Please find the original thread on sage-support at
> https://groups.google.com/group/sage-support/browse_thread/thread/39b019cd51270574]
>
> When trying to run the following code to solve a sytem of ODEs, sage
> spawns an error message:
>
> ------------------------------
> t = var ('t')
>
> S_0 = 1.5
> X_0 = 0.05
> Y_XS = 0.5
> K_S = 0.007
> mu_max = 0.8
>
> X = function ('X', t)
> S = function ('S', X)
>
> def mu (S):
> return (mu_max * S) / (K_S + S)
>
> dXdt = diff (X, t) == mu (S) * X
> dSdt = diff (S, t) == -mu (S) * X / Y_XS
>
> desolve_system ([dXdt, dSdt], [X, S], ics = [0, X_0, S_0])
> ------------------------------
>
>
> Traceback:
>
> ------------------------------
> Traceback (most recent call last): Y_XS = 0.5
> File "", line 1, in <module>
>
> File "/tmp/tmpS9OrMD/___code___.py", line 22, in <module>
> exec compile(u'desolve_system ([dXdt, dSdt], [X, S], ics =
> [_sage_const_0 , X_0, S_0])
> File "", line 1, in <module>
>
> File
> "/opt/sage/local/lib/python2.6/site-packages/sage/calculus/desolvers.py",
> line 628, in desolve_system
> dvar.atvalue(ivar==ivar_ic, ic)
> File
> "/opt/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py",
> line 1408, in __call__
> return self._obj.parent().function_call(self._name, [self._obj] +
> list(args), kwds)
> File
> "/opt/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py",
> line 1316, in function_call
> return self.new(s)
> File
> "/opt/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py",
> line 1097, in new
> return self(code)
> File
> "/opt/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py",
> line 1032, in __call__
> return cls(self, x, name=name)
> File
> "/opt/sage/local/lib/python2.6/site-packages/sage/interfaces/expect.py",
> line 1451, in __init__
> raise TypeError, x
> TypeError: Error executing code in Maxima
> CODE:
> sage15 : atvalue(sage9,sage13,sage14)$
> Maxima ERROR:
>
> Improper argument to atvalue:
> ['X(t)]
> -- an error. To debug this try: debugmode(true);
> ------------------------------
>
> This is sage 4.5.2 on Linux x86.
>
> If further (debugging) info is required, please let me know.
This appears to be what raises the error:
var('t')
X = function('X', t)
S = function('S', X)
S._maxima_().atvalue(t==0, 1.5)
Either of
atvalue(S(X(t)), t=0, 1.5);
atvalue('S('X(t)), t=0, 1.5);
gives this error in Maxima (run with 'sage -maxima'):
Improper argument to atvalue:
[X(t)]
-- an error. To debug this try: debugmode(true);
Does atvalue work with composed functions?
Do X and S depend linearly on each other in your example? What if you
eliminate one and try to solve the remaining ODE?
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