[SciPy-User] problem using optimize.root

[Slavin, Jonathan]

Hi,

I'm trying to solve a two-point boundary value problem using odeint in
conjunction with root.  I've written a function (the objective function)
that takes as an argument the eigenvalue for the problem and returns the
difference between the endpoint value for one of the variables and the
desired value.  So the function calls odeint with extra arguments that give
the initial conditions at the left boundary as well as the eigenvalue.  I
can call this function perfectly well from the prompt and it behaves as
expected but when I run it within the call to scipy.optimize.root I get the
following error:
...
/export/slavin/python/anaconda/lib/python2.7/site-packages/scipy/integrate/odepack.pyc
in odeint(func, y0, t, args, Dfun, col_deriv, full_output, ml, mu, rtol,
atol, tcrit, h0, hmax, hmin, ixpr, mxstep, mxhnil, mxordn, mxords,
printmessg)
    146     output = _odepack.odeint(func, y0, t, args, Dfun, col_deriv,
ml, mu,
    147                              full_output, rtol, atol, tcrit, h0,
hmax, hmin,
--> 148                              ixpr, mxstep, mxhnil, mxordn, mxords)
    149     if output[-1] < 0:
    150         print(_msgs[output[-1]])

TypeError: Cannot cast array data from dtype('O') to dtype('float64')
according to the rule 'safe'
>
/export/slavin/python/anaconda/lib/python2.7/site-packages/scipy/integrate/odepack.py(148)odeint()
    147                              full_output, rtol, atol, tcrit, h0,
hmax, hmin,
--> 148                              ixpr, mxstep, mxhnil, mxordn, mxords)
    149     if output[-1] < 0:

So when root calls the function, which in turn calls odeint, something that
was previously of float type somehow gets the dtype of object.  I've used
pdb within ipython to try to find what is happening, but it seems that all
the inputs to odeint are of the correct dtype.  Any help would be
appreciated.

Regards,
Jon

-- 
________________________________________________________
Jonathan D. Slavin                 Harvard-Smithsonian CfA
jslavin at cfa.harvard.edu       60 Garden Street, MS 83
phone: (617) 496-7981       Cambridge, MA 02138-1516
fax: (617) 496-7577            USA
________________________________________________________
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