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Re: NDSolve - Nice function but stiffness-problem


U¿ytkownik "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de> napisa³ w 
wiadomo¶ci news:ghavmr$o6o$1 at smc.vnet.net...
> 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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