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Round MOD to lower depths

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When computing the suggested switch depth for a gas,
we should take the next stop depth above the MOD, i.e.
round down. Otherwise we can produce MOD violation warnings.

We need, however, a bit of fudge as otherwise we do not
suggest to switch to o2 at 6m.

TestPlan uses the MOD to determine the depth to switch to
Tx21/35. This happens to be 65.378m. Therefore, switching
at 66m violates the MOD, the switch should be at 63m.
This then affects the gas usage.

Signed-off-by: Robert C. Helling <helling@atdotde.de>
This commit is contained in:
Robert C. Helling 2024-11-15 00:47:40 +01:00 • committed by Michael Keller
parent a898173ce7
commit 7dc92e170f
2 changed files with 6 additions and 4 deletions
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4
core/dive.cpp
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@ -2457,7 +2457,9 @@ int dive::mbar_to_depth(int mbar) const
depth_t dive::gas_mod(struct gasmix mix, pressure_t po2_limit, int roundto) const
{
double depth = (double) mbar_to_depth(po2_limit.mbar * 1000 / get_o2(mix));
return depth_t { .mm = int_cast<int>(depth / roundto) * roundto };
// Rounding should be towards lower=safer depths but we give a bit
// of fudge to all to switch to o2 at 6m. So from .9 we round up.
return depth_t { .mm = (int)(depth / roundto + 0.1) * roundto };
}
/* Maximum narcotic depth rounded to multiples of roundto mm */