Fix per-cylinder SAC rate calculations when cylinder use isn't known

John Van Ostrand reports that when he dives using two cylinders using
sidemounts, the per-cylinder SAC rate display is very misleading.

What happens is that since the two cylinders are used together (but
without a manifold), John is alternating between the two but not
actually adding gas switches in the profile.  As a result, the profile
looks like only one cylinder is used, even though clearly the other
cylinder gets breathed down too.

The per-cylinder SAC rate calculations would entirely ignore the
cylinder that didn't have gas switch events to it, and looking at the
info window it would look like John had a truly exceptional SAC rate.

But then in the general statistics panel that actually takes the whole
gas use into account, the very different real SAC rate would show up.

The basic issue is that if we don't have full use information for the
different cylinders, we would account the whole dive to just a partial
set.  We did have a special case for this, but that special case only
really worked if the first cylinder truly was the only cylinder used.

This patch makes us see the difference between "only one cylinder was
used, and I can use the overall mean depth for it" and "more than one
cylinder was used, but I don't know what the mean depths might be".

Reported-by: John Van Ostrand <john@vanostrand.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

0 files changed, 0 insertions, 0 deletions