[PULL REQUEST] VPM-B

[Rick Walsh]

On 18 Aug 2015 12:13 am, "Jan Darowski" <jan.darowski at gmail.com> wrote:
>
> > I think I've worked out at least one difference in the programs'
algorithms,
> > and sorry I doubt you'll like it.  Subsurface calculates required stops
> > considering the ascent rate and the time to reach the stop.  The Fortran
> > program calculates the 'instantaneous' ceiling, i.e. the depth
corresponding
> > to the tolerated ambient pressure according to the current allowable
> > pressure gradient.  More fun!
> >
> > Which approach is more justified?  Debatable.  The method used by
Subsurface
> > should be 'better', but when the depth of the first stop/ceiling is
given a
> > special significance thanks to the Boyles law compensation process, I'm
not
> > so sure.  The 'instantaneous' ceiling method is more conservative, and,
> > without having modified the code and tested, I'm guessing would produce
deco
> > schedules more consistent with other VPM-B programs.
> >
> > R
> >
>
> I expected something like this... calculations are checked, gradients
> are checked. It had to be something "mechanical". For the examples
> you've posted I got 16 vs 16min and 46 vs 49min after the fix (in
> trial_ascent I changed the segment time to 0 and added one more place
> for boyles_compensation).
>
> Thanks a lot for this, I spent many days on searching for bugs in this
> code. I suppose there can be some other small issues but this one
> explains a lot.
>
> Today there will be a patch for this.
>

Great, I'm glad it wasn't too painful.

Make sure not to break the current method for the Buhlmann model.  That
works well as it is.

> --
> Jan Darowski
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