subsurface crash when merging .xml files

[Alessandro Volpi]

Thanks for the explanation.

Alessandro

On Fri, Mar 3, 2017 at 7:30 PM, Linus Torvalds <
torvalds at linux-foundation.org> wrote:

> On Fri, Mar 3, 2017 at 2:59 AM, Alessandro Volpi <volpial at gmail.com>
> wrote:
> >
> > The only remaining question is : why is the tank start pressure redundant
> > field present only in a few dives, as the data are imported with
> smk2ssrf ?
> > I have observed that all records with the redundant data have been
> generated
> > by the SmartTec dive computer whilst the old Aladin Air Z O2 and the new
> > Galileo Sol and Galileo Trimix are not affected.
>
> The reason is probably just that the SmartTec import had the dive
> computer always remember and download first/last pressure data, and
> then it ignores it if it's "close enough" to the sample data.
>
> And that's exactly what subsurface does too, except the rules for
> "close enough" probably differ.
>
> In subsurface, the "redundancy" check is whether the samples are
> within half a bar of the reported pressure (see
> same_rounded_pressure() in core/dive.c - the "500" constant is because
> we do things in millibar internally, of course).
>
> For imperial divers, that's about a 8 PSI difference where we say that
> the pressures are effectively the same.
>
> I suspect that the SmartTec import has something similar, but maybe
> the SmartTec redundancy check is tighter. Maybe it's just 0.1 bar
> instead of 0.5 bar. Or, if they work natively in PSI, maybe they cut
> off at 1PSI differences or something.
>
> As to why the dive computer would report different values to begin
> with: I think your theory is right that you just turned on the dive
> computer earlier, and then just test-breathing at the surface (or
> temperature changes or whatever) means that the early cylinder
> pressures are different from the first few samples. Or maybe the
> sensor just fluctuated a bit.
>
>                      Linus
>
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