Hi, thanks for verification. 2015-07-15 14:49 GMT+02:00 Rick Walsh <rickmwa...@gmail.com>: > Jan, > > I was curious and had a peek at your github. I hope you don't mind. > Robert's feedback is what you should be most interested in, but I'll give > mine anyway. > https://github.com/Slagvi/subsurface boyle > > On 15 July 2015 at 06:31, Jan Darowski <jan.darow...@gmail.com> wrote: >> >> Yes, I've seen this link first time you sent it. Parameters are not >> the problem here. We have a different tissue saturation calculation >> method, so results differ a little bit at the beginning of the ascent. >> So the first stop is a little bit later (6m), It has a big influence >> on the total deco time because later gradients are calculated against >> this depth. > > > The first thing I noticed was that the critical radii for N2 and He were > still 0.8 and 0.7 microns, which is the usual setting for VPM without Boyles > law compensation. With Boyles law compensation, 0.55 and 0.45 microns are > generally considered to be the nominal values (zero conservatism). This > means that your model was being more conservative than V-Planner's most > conservative (+4) setting, which increases the critical radii by 35%. It is > not surprising you've been getting huge decompression times.
I know about the radii, it will be fixed with next pull request but If I have it set on the same values in both programs, it shouldn't be a problem. (But right now its 0.6 and 0.5, not 0.8, 0.7). > After changing the critical radii, I compared the total ascent times to > published results from V-Planner for 200ft and 300ft trimix dives. Links to > pdf files are about 1/3 of the way down the page. > http://www.decompression.org/maiken/VPM/VPM_Publications.htm > > Just looking at the total ascent time and depth of the first stop, the match > is very good for the 200 ft dives in the 20-60min bottom time range (all > total ascent times within 1minute, and appears to be the same first stop > depth). This is impressive. > > For a 10min bottom time, Subsurface was 3min more conservative, and for >>60min bottom time, Subsurface was progressively less conservative than the > V-Planner profiles (e.g. 10min difference in ascent time for 120min bottom > time). > > For the 300ft dives, Subsurface was less conservative than the V-Planner > profiles. > > Could the differences for longer and deeper dives be due to the critical > volume algorithm you mentioned you needed to investigate further? I was checking against C implementation from github (which is the easiest for quick modifications and additional data extraction and also is an original codes direct translation). After finding two more bugs I got around 20min of difference with the depth of 80m and 30min at the bottom (15/45 mix). CVA can't be a problem as I switched it off to isolate the Boyles influence. I suspect one more place: the original implementation uses projected depths (estimates some maximum depth the diver can ascend to) and later verifies it but only in one direction. So maybe, that's why for deeper dives it's more conservative. For sure, original implementation has slightly different saturation results. But tracing it and saying which way it changes the schedule is terrible as it depends on the depth. I would say that <10% of deco time difference is the limit. As long as we can stay there, it's fine. If you just play with the bottom time (for example increase it by 1-2min), you can see that the original code generates very uneven schedules. -- Jan Darowski _______________________________________________ subsurface mailing list subsurface@subsurface-divelog.org http://lists.subsurface-divelog.org/cgi-bin/mailman/listinfo/subsurface
