Rebreather World - View Single Post - New FREE Beta Deco Software for Linux/Mac/Windows

brockbr · 17th April 2008, 14:36

Quote: (Originally Posted by Stephane)

Hi,

What are the descent and ascent rate?
I'm comparing with MV-Plan and I find big differences:
GF 30-75, 210ft for 25mn on a 10/52 mix, SP=1.3, you soft gets me out in 71mn and MV-Plan in 96mn (84mn with VPMB +4 conservatism).

Stephane,
There is no padding or conservatism built into the algorithm as I've implemented it, only straight Buhlmann/16 with GF support.

Of course, I don't know the internal workings of MV-Plan, but I'd have to wonder if they cut plans directly at the Buhlmann numbers or not.

At any rate, this is a great observation - The shallow stops don't look right to me (20 - 1, 10 - 1). Let me look into this exact example and see if I can figure out what's causing the shallow stops to be so short.

BTW - The descent and ascent rates are set at 1 BAR min (1 ATM, 33 Ft, etc), to be conservative. I'm going to allow these to be set in future builds.

501 Minute Stops
Also - A few people have pointed out that some shallow stops appear at 501 min. The reason for these is that the Buhlmann model includes absolute pressures that are allowable for any given compartment considering the loading. What's happening is that as you get near the surface, mathematically it gets closer and closer to a rounding error to get you out of the water. In some case, this rounding error won't allow the model to off gas any further (becoming balanced as at would at the surface), and it spins off. I put a hard limit of 500 minutes - So 501 is a by-product of the math exhibiting this error.... This is why we test

I'm working on ways to address this.

b.

17th April 2008, 14:36	#30 (permalink)
brockbr Train Wrecked ;) Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Dec 2007 Location: Alabaster, AL Posts: 223	Re: New FREE Beta Deco Software for Linux/Mac/Windows - Need Testers Quote: (Originally Posted by Stephane) Hi, What are the descent and ascent rate? I'm comparing with MV-Plan and I find big differences: GF 30-75, 210ft for 25mn on a 10/52 mix, SP=1.3, you soft gets me out in 71mn and MV-Plan in 96mn (84mn with VPMB +4 conservatism). Stephane, There is no padding or conservatism built into the algorithm as I've implemented it, only straight Buhlmann/16 with GF support. Of course, I don't know the internal workings of MV-Plan, but I'd have to wonder if they cut plans directly at the Buhlmann numbers or not. At any rate, this is a great observation - The shallow stops don't look right to me (20 - 1, 10 - 1). Let me look into this exact example and see if I can figure out what's causing the shallow stops to be so short. BTW - The descent and ascent rates are set at 1 BAR min (1 ATM, 33 Ft, etc), to be conservative. I'm going to allow these to be set in future builds. 501 Minute Stops Also - A few people have pointed out that some shallow stops appear at 501 min. The reason for these is that the Buhlmann model includes absolute pressures that are allowable for any given compartment considering the loading. What's happening is that as you get near the surface, mathematically it gets closer and closer to a rounding error to get you out of the water. In some case, this rounding error won't allow the model to off gas any further (becoming balanced as at would at the surface), and it spins off. I put a hard limit of 500 minutes - So 501 is a by-product of the math exhibiting this error.... This is why we test I'm working on ways to address this. b. Last edited by brockbr : 17th April 2008 at 14:41.
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