DAESL implementation problem

[maximus]

Dear all,

I am trying to change the solver for our system of ordinary differential equations from IVPAG to DAESL. My code is running flawlessly with the IVPAG solver, which requires the form y' = f(t,y). DAESL on the other hand requires an implicit formulation of the form 0 = g(t,y',y). Rewriting the system is thus easily done.

DAESL is correctly initialized, and I call it with the following arguments:

 call D_DAESL(t, tend, ido, Y, YPRIME, GCN, IYPR = 0, IUJAC = 0, MATSTR = 0, ISOLVE = 0, ML = neq - 1, MU = neq - 1, &
    RTOL = 1.d-4, H0=0.d0, HMAX=0.d-6, MAXORD = 5, MAXSTEPS = 10000)

Note that IYPR = 0 because I am certain that YPRIME is initialized such that 0 = g(t,y',y).


In the first time step I receive the error:

***FATAL       ERROR 10 from DDAESL. The iteration matrix is singular

I do not understand what the iteration matrix is. Does it refer to the Jacobian (termed partial derivative matrix in the documentation) of g?

Thx for any suggestions.

max

[mecej4]

It is not clear to me why you wish to use a DAE solver when your problem is just an ODE IVP. DAESL has a more complex calling sequence and many more usage options, and these features create more opportunities for introducing errors.