Hi,
Le 30/10/2014 18:17, Linus Torvalds a écrit :
There's some more docs from Suunto at
http://ns.suunto.com/pdf/Suunto_RGBM.pdfif some mathematically inclined person cares and is interested. And I can give people profiles and tissue loading data from my 21 dives if somebody really wants to see if they can match the data at least superficially.
The RGBM algorithm is documented in details here: http://www.scuba-doc.com/rgbm.pdf. Unfortunately, the article (and Wienke's books) is quite difficult to follow. I'm not a native English speaker, but the style feels awkward. And while I'm a researcher in statistics I don't understand everything. I've access to research papers published by Wienke (not all but a good selection of it through my university's subscription) but that does not help much... I can share some docs if someone's interested. Gap has also a technical primer on how they implemented RGBM: http://www.gap-software.com/staticfiles/RGBMmath.pdf. Not super clear.
From what I've gathered, the RGBM works as the VPM by tracking bubble
growth, more precisely the effect of pressure change on the distribution of the radius of the bubbles in the tissues. The idea is that small bubbles will vanish naturally whereas big ones will grow, leading to a notion of critical phase volume: basically, you don't want too much bubbles with a radius above some critical excitation radius. VPM and RGBM use similar approach, but the bubble growth model of RGBM is more complicated.
The main difference with Bühlmann approach and VPM/RGBM is the way the allowed gradient is calculated, not the way the gas pressure in compartment is tracked (which is pretty basic stuff). The original RGBM implementation uses a lot of compartment while Suunto's version is down to 9 (or 15? Suunto's doc says 9). If I understand correctly, this means that the tissue saturations tracked by the EON steel should be comparable to the ones tracked by any other computer, provided the half lifes match.
I've not followed subsurface discussions lately, so I'm not sure if a VPM implementation is still under consideration (it was discussed at some time). My impression is that VPM is already a bit convolved mathematically so it would be probably better to start with it before RGBM which is a step further away from the simple Bühlmann approach.
Hope that helps.
Fabrice