recording singularities of NDSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg80500] recording singularities of NDSolve*From*: "Judith Bunder" <bunder at phys.cts.nthu.edu.tw>*Date*: Thu, 23 Aug 2007 06:23:37 -0400 (EDT)

Hi, I have to solve a system of simultaneous equations and I have to solve them several times with varying initial conditions. I use something like this: Do[{c1 = i/imax, c2 = j /jmax, sol[i, j] = First@NDSolve[eqns, coup, {t, 0, 100}]}, {j, 1, 5}, {i, 1, 5}] So, I solve the the problem 25 times with 5 different j values and 5 different i values. The variables c1 and c2 are the variable initial conditions. I have no problems with this part. My problem is, sometimes the solution diverges. This is good, I'm looking for divergent points. But, I want some method of recording where the solution diverges. I get the warning messages: NDSolve::ndsz At t=18.28484703670573` step size is effectively zero; singularity or stiff system suspected. so I could manually record this value of t. But, this isn't practical as several of my 25 solutions are usually divergent (and I also need to record the value of i and j). Is there any way to define something like t-div[i,j] which will record all these points where my solution diverges? Thanks in advance, Judy