Mares Sirius, another computer running Buhlmann

[dmaziuk]

I expect you could tweak the "gradient reduction factors" to e.g. generate shallower stops, reduce the "repetitive diving" penalty, etc., but there was only one person on the planet who understood exactly how to tweak them to the desired effect.

 

[lowwall]

Unfortunately…I bought a lightly used Genius and transmitter from my LDS 2 months ago on deep discount before this was announced.

They came out with a new transmitter too for the Sirius that isn’t backward compatible and the Genius transmitter is not forward compatible.

Us Genius AI owners just got boxed out of the future. Doh!

It's tech. Something better is always going to come along. If you were happy with the price and features at purchase, it's a win.

 

[Belzelbub]

It's tech. Something better is always going to come along. If you were happy with the price and features at purchase, it's a win.

Sure. If it's really better. In this case, it's not exactly clear that something is better. It uses a different battery, but otherwise seems to perform the same basic function. I'm not sure I understand why this is necessarily better, and if it is indeed better, why couldn't it be backwards compatible.

 

[Jai Bar]

If you look closely I think you'll find that all those brands' algorithms were developed in collaboration with the late Dr. Wienke. I am guessing the "late" part there makes it difficult for them to update the models to the newer thinking, and quite possibly: even to update the code to the newer hardware.

There is an alternative that happens to be everybody's darling du jour, is royalty-free, and is pretty straightforward to implement. What's a vendor to do?

Uh, what has it got to be with the "late" part? Like Buhlman passed away so many years before Wienke, and the algorithm bearing his name was developed in the 60s, a modification on Haldane's theory from more than a 100 years ago?

These works are all published and well established- some basic equations, it is not some smartphone app that needs updating and some periodical coding to iron bugs, whereas implementation to hardware is not as complex as you'd imagine. There is no "newer thinking" on these simple models- they sort of work and implemented on a large array of things other than decompression theory. That's the beauty of it and why they are still around for so many years.

For what's it's worth, Wienke's RGBM is a different approach than Buhlman and Haldane compartment models which are based on several compartments representig various tissues, each with a different time constant. RGBM on the other hand may be considered "new thinking" instead of tissue compartments the diffusion of gasses through membranes of bubbles, and there are a few other similar models around too.

In the end, both and all models are just models. They fit most of the diving population and considered in general safe.

 

[dmaziuk]

These works are all published and well established- some basic equations, it is not some smartphone app that needs updating and some periodical coding to iron bugs, whereas implementation to hardware is not as complex as you'd imagine.

Cite please. Show me where any flavour of RGBM is actually published, then talk.

 

[scubadada]

Cite please. Show me where any flavour of RGBM is actually published, then talk.

I have never seen or heard that the full details of any of the RGBM decompression algorithms by Suunto, Mares, or Cressi are available in the public domain. The general information released by Suunto on their RGBM, Technical RGBM, Fused RGBM, and Fused RGBM 2 algorithms makes it clear that they were all developed with Bruce Wienke.

Suunto RGBM Dive Algorithms

www.suunto.com

Though Dr Wienke died nearly 3 years ago, I would have thought that all the required information resided within the companies deploying RGBM deco algorithms and that they had the technical expertise to accurately revise them. My assumptions may or may not be correct.

Perhaps this is a reason that Suunto and Mares have started offering Buhlmann ZH-L16C with GF on their computers. Suunto offers Buhlmann on the Eon Steel. Mares offers Buhlmann on the Genius and on the Sirius, the topic of this thread. Seems as if Cressi is the only one that has not come around, yet

 

[Jai Bar]

Cite please. Show me where any flavour of RGBM is actually published, then talk.

Reduced gradient bubble model - PubMed

An approach to decompression modeling, the reduced gradient bubble model (RGBM), is developed from the critical phase hypothesis. The phase limit is introduced, extended, and applied within bubble-nucleation theory proposed by Yount. Much is different in the RGBM algorithm, on both theoretical...

pubmed.ncbi.nlm.nih.gov

This one is also useful- I used it in the past to write a Matlab simulation for comparison with compartment models:

https://www.tecvault.t101.ro/ModernDecompression_Wienke.pdf

More sources:

[PDF] Rgbm Algorithm Overview: Concepts, Bases, Validation, Testing and References | Semantic Scholar

Gas exchange, bubble formation and elimination, and compression-decompression in blood and tissues are governed by many factors, such as diffusion, perfusion, phase separation and equilibration, nucleation and cavitation, local fluid shifts, and combinations thereof. Owing to the complexity of...

www.semanticscholar.org

Lots of full-text available here, extensive work of the late Dr Wienke:

https://www.researchgate.net/profile/B-Wienke/research

 

[dmaziuk]

Reduced gradient bubble model - PubMed

An approach to decompression modeling, the reduced gradient bubble model (RGBM), is developed from the critical phase hypothesis. The phase limit is introduced, extended, and applied within bubble-nucleation theory proposed by Yount. Much is different in the RGBM algorithm, on both theoretical...

pubmed.ncbi.nlm.nih.gov

Thank you, forgot about this one. The one from 2004 appears to be unobtainable, which curiously coincides with Maiken's rant:

Even today, in 2004, it can be demonstrated from commercial programs that the "full-up" RGBM is still underpinned by Yount and Hoffman's iterative algorithm. With the wide distribution of open source VPM, Wienke was placed under pressure to differentiate his product by customers who had paid for material that could be obtained virtually for free. Since 2002, this has resulted in a new RGBM model, publicized in dive industry print and venues.

-- VPM Algorithim

Out of curiousity, how far did you get with your matlab sim? I find the couple of Wienke's papers that have actual formulae in them somewhat... handwave-y. But anyway, in the context of this thread: I don't know if Mares has any computers in their product line that implement "full" RGBM: AFAIK all low-end devices run something called "folded RGBM" and only high-end Suuntos implement the "real RGBM" (but only if you go deep enough long enough). I.e. whatever's actually implemented in most "RGBM" computers remains anyone's guess.

So then you have a next generation of programmers trying to retrofit that to the next generation of microprocessors with at best a very fuzzy idea of FTW they're looking at... I'd ditch it and go ZH-L too, and save a bundle on the licensing fees in the process, even if bubble models weren't falling out of fashion.

 

[scubadada]

... I'd ditch it and go ZH-L too,..

Buhlmann with gradient factors, presets or presets and custom is expanding rapidly. It's not only RGBM brands like Suunto and Mares. Some brands have all their computers running Buhlmann, some are just breaking in with new models. A list, perhaps not complete, includes:
Apeks
Aqua Lung
Atmos
Crest/Genesis/Deep 6
Divesoft
Garmin
Heinrichs Weikamp (not avail US)
Mares
Oceanic (Oceanic+ on the Apple watch Ultra)
Ratio
Scubapro
Seac
Shearwater
Suunto

I would hazard a guess that not only RGBM, but other proprietary algorithms are generally on their way out. I guess we will all see.

 

[Diver.Jason]

I have been looking for a new wrist-worn computer that I would like to double as a daily watch. I am not a Garmin fan, I live down the street from their headquarters and hear all kinds of stuff like no one who works on the product line, actually likes to dive. I was getting ready to pull the trigger on a Teric, but saw this and it gave me pause. Not much in the form of videos or reviews to compare to. But if anyone has had real-world comparisons to share, I would certainly welcome it. My local dive shop is working on getting a demo model to play with, but I would like something in the meantime. I know this thing is brand new and it will probably take some time, but this is the first spot I thought to check-in.

Thank in advance.