Re: NDSolve problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg31746] Re: NDSolve problem*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Sat, 1 Dec 2001 02:43:32 -0500 (EST)*Organization*: Universitaet Leipzig*References*: <9u4gqb$lpb$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, your system of equations has a singularity at this point and one of the components goes to infinity. The stepsize control detect the singularity and reduce the stepsize until it is to small. You should care full analyse the differential equation if the singularity is not expected/obvious. With an ordinary differntial equations solver it is impossible to jump over the singularity, because the most ode solver use a polynomial approximation to the solution and you can't approximate 1/x with a polynomial of positive powers. Regards Jens deniz.seker at arcelik.com.tr wrote: > > Hi, > > I have a problem with NDSolve. I'm trying to solve 2 coupled differential > equations. But dur,ng the solution, I saw a message that,"At t=.... step > size is effect,vely zero, singularity suspected." Then, I'm trying to > decrease StartingStepSize option up to 10^(-14) or increase MaxSteps to > 100000. But, for these two cases, I couldn't get solutions for 6 hours run. > What should I do? > > Best regards, > > Deniz > > PS : If anybody wants to see the notebook, I can send via e-mail.