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[Octave-bug-tracker] [bug #49408] ode{23, 45} option "Refine" has no eff
From: |
Rik |
Subject: |
[Octave-bug-tracker] [bug #49408] ode{23, 45} option "Refine" has no effect |
Date: |
Fri, 21 Oct 2016 22:33:14 +0000 (UTC) |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:43.0) Gecko/20100101 Firefox/43.0 |
Update of bug #49408 (project octave):
Status: None => Confirmed
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Follow-up Comment #1:
Further clarification, the integrated function myfun is
myfun = @(t, y) 1;
With the Refine option set to 1, only the principal timesteps are calculated.
Under Matlab, the code below chooses just 4 time steps.
myfun = @(t, y) 1;
[t, y] = ode45 (myfun, [0 1], 1, odeset ('maxstep', 1, 'initialstep', .1,
'refine', 1));
t'
ans =
0 0.1000 0.6000 1.0000
When Refine is an integer N greater than 1 then N-1 intermediate timesteps are
calculated. So, the three gaps between the principal timesteps should each
get 2 smaller timesteps. This is indeed what happens under Matlab.
myfun = @(t, y) 1;
[t, y] = ode45 (myfun, [0 1], 1, odeset ('maxstep', 1, 'initialstep', .1,
'refine', 3));
t'
ans =
0 0.0333 0.0667 0.1000 0.2667 0.4333 0.6000
0.7333 0.8667 1.0000
Under Octave, the solver, without the Refine option, chooses 6 principal
timesteps. I don't think this is an issue, just a difference from Matlab.
However, when the Refine option is used, Octave does not generate any
intermediate timesteps which is a problem.
_______________________________________________________
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<http://savannah.gnu.org/bugs/?49408>
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- [Octave-bug-tracker] [bug #49408] ode{23, 45} option "Refine" has no effect,
Rik <=