- The challenges are that there really aren't just 3-4 algorithms. Nearly every manufacturer plays with their installation in some way.
This is very true. Each implementation can vary. And how the algorithm is implemented in real time can vary even more. How are unexpected events, like re-descending after a partially completed schedule handled? If you miss a deco stop by 15 seconds, will you be locked out? If you are diving in the 15-30 foot range, will you get a great many safety stops?
- For those using bubble theory, to Dr. Pollacks knowledge, nobody has yet measured a bubble. The theories are algorithms and are not vetted by the community as a whole.
Not sure what this means. Certainly the physics of bubble formation are well understood and we have “measured” many bubbles- which is not to say that in a real world human body there are not many variables we can’t effectively track or model or test for except by inference from results. I think the divide is more between those starting from a clinical model, derived from experience or animal experimentation, which means they come mostly from the medical side, and those starting from the physics side, a physical model that is then verified by clinical experiment. There are different cultures within science.
- Less expensive computers are likely to not have the computing power to model a theory effectively using, for example, 16 tissue samples. Many calculate on three, for example, and then extrapolate from there.
There is
some truth to this, but only to a point. Running a fully iterative bubble model is very computational intensive, regardless of the number of tissue groups- and number of tissue groups is not necessarily a “more is better” situation, these are just mathematical abstractions. You can create precision without adding any accuracy. It’s not necessarily related to the price of the computer. Suunto’s “RGBM” for instance (which comes in some pretty pricy computers) is a basically Haldanian model that is tweaked with factors that cause it to closely approximate a fully iterative bubble model without having to actually run the calculations in real time. To my knowledge, only the Atomic Cobalt comes pre packaged running- in real time- a fully iterative bubble model (with 15 tissue groups), and that only kicks in if you dive below 150’, shallower dives are on a “folded” algorithm. Liquivision and Shearwater both offer fully iterative bubble models as an upgrade. But the vast majority of dive computers are running some kind of basically Haldanian or Buhlmann algorithm, using M-values, and work in much the same way.
Thanks to the mobile device industry, computational power that runs from batteries is a lot cheaper now. This is more a question of firmware complexity than cost.
- If you look at the past few years, many of the bubble based computers, that used to get you out of the water so quickly, have had levels of conservatism added that see to make them more Buhlmann like.
True. There has been a convergence in many models- some have aded bubble factors and deep stops, some iterative bubble algorithms have been tweaked to become more conservative.
It’s a very fuzzy subject. But the variation between individuals and their deco tolerance based on unaccounted for factors is probably greater than the variation in algorithms. The idea that DAN or anyone else could effectively test algorithms in the abstract, in any meaningful way- apart from what they do now, monitoring large statistical databases- implies a level of precision that just is not there in the field. All dive computers are a general guide, they don't know what is going on in your body.
