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[Octave-bug-tracker] [bug #49190] no return to prompt by ode45() when bl
From: |
Carlo de Falco |
Subject: |
[Octave-bug-tracker] [bug #49190] no return to prompt by ode45() when blowup of solution occurs |
Date: |
Tue, 27 Sep 2016 12:37:27 +0000 (UTC) |
User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:48.0) Gecko/20100101 Firefox/48.0 |
Follow-up Comment #5, bug #49190 (project octave):
Andreas,
The 'problem dependence' is given by the fact
that the choice of minimum time step for which
to stop integrating is given by the location of
the blow up, i.e., for
x'= 1+x^2 => blowup at t=pi/2
the integration will stop when the
estimated dt = eps(pi/2) = 2.2204e-16
for
x'= 2*(1+x^2) => blowup at t=pi/4
the integration will stop when the
estimated dt = eps(pi/4) = 1.1102e-16
AFAIU, in the old version the minimum time
step was computed as eps (tspan(2) - tspan(1))
which would have been eps (2) = 4.4409e-16
in both cases.
the choice made by matlab also depends on the
problem (i.e. it depends on the location of
the blow-up) but the value that matlab chooses
is consistently larger than mine and I couldn't
find anywhere documentation of its particular choice
c.
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