       Re: NDSolve - Nice function but stiffness-problem

• To: mathgroup at smc.vnet.net
• Subject: [mg96471] Re: NDSolve - Nice function but stiffness-problem
• From: "slawek" <human at site.pl>
• Date: Sat, 14 Feb 2009 03:09:59 -0500 (EST)
• References: <gh8hih\$qv5\$1@smc.vnet.net> <ghavmr\$o6o\$1@smc.vnet.net>

```U¿ytkownik "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de> napisa³ w
> for larger A, f[x] change the sign and than no solution
> for the boundary value problem exist any more.
> Mathematica report the x position where f[x] become
> negative.

False, D[f[x],x]==Exp[A f[x]] is an evolution equation, i.e.

Loop with stepsize going to null
fnew = fold + stepsize * Exp[A fold]
end loop

If an start value exist for the first fold there is no reason to
"nonexistence" of another fnew. A one step more is always possible.

slawek

```

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