[Octave-bug-tracker] [bug #49190] no return to prompt by ode45() when blowup of solution occurs

[Carlo de Falco]

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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