Subsurface deco calculations

Willem Ferguson willemferguson at
Wed Feb 8 22:42:07 PST 2017

On 09/02/2017 06:23, Linus Torvalds wrote:
> We never renumber or delete cylinders on our own - we just ignore 
> unused cylinders at the end.
> So when you download from the OSTC first, you actually have four 
> cylinders defined, and the second one is the one you are using. If you 
> look at the XML, you'll see all four cylinders.
> The first cylinder is an air one that you never use, but we don't 
> delete it just because you didn't use it. You had it in your dive 
> computer, we keep it around.
> In fact we keep the other two around too, but we have that crazy logic 
> where we don't show them because they are at the end and not used. We 
> should stop doing that too, but Dirk added it for some broken dive 
> computers that always reported eight cylinders or something like that.
> When you download from the vyper first, the 32% cylinder ends up being 
> the first one, and you still have the other three cylinders that the 
> OSTC reports, but now they are all at the end so they get hidden by 
> that same crazy logic.
>     BTW what is the flags in the event tag?
> Not really used any more. We used to encode the cylinder number in the 
> flags (because libdivecomputer didn't give it any sane way), but now 
> it's just legacy noise that doesn't get renumbered. So it was the 
> first cylinder for the vyper, and it is still flags=1 for that one, 
> and it was the second cylinder for the OSTC, so it's flags=2 for that one.
>         Linus
Remember that these approaches towards non-used cylinders need to take 
into account the setting in Preferences->Graph: Misc. Show unused 
cylinders in equipment tab.
I will eventually have to write about this in the user manual. So if the 
management unused cylinders is easy to explain, that will really help.
I will do some testing of this using some dive plans, once the patch has 
been pulled into master. It appears pretty useful.
Kind regards,

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