Don't do this expensive calculation when not needed.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Other VPM-B implementations (V-Planner, MultiDeco, Fortran code) take the
default gradient of onset of impermeability as 8.2 atm. We use bar as the
pressure unit, and 8.2 atm = 8.30865 bar.
This has negligible effect on all of the calculated plans I've tested, resulting
in a maximum decrease of 1 minute in total dive time for ~150 m deep dives, but
we should get unit conversions correct anyway.
Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Subsurface appears to produce marginally less conservative plans than our
benchmarks. Introduce 1% additional conservatism.
Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
So far, add_segment() returned a tissue tolerance (i.e. ceiling)
computed just in its return statement. This tissue_tolerance
needed to be dragged around until it was needed or be dropped
if not needed at all.
As for VPM-B, this ceiling computation is a bit expensive, this patch
calls the computation function tissue_tolerance_calc() when the
value is actually needed and not before.
This changes the signature of some functions.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
and not some time before and store the result in a global variable.
This stores only the bottom gradients and computes the Boyle compensation
when computing the allowed ambient pressure.
As the Boyle compensation needs a reference ambient pressure, to find the ceiling,
we have to iterate this computation until the reference pressure is close enough to
the ceiling.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Inspired gas loading equations depend on the partial pressure of inert gas in
the alveolar.
P_alv = (P_amb - P_H2O + (1 - Rq) / Rq * P_CO2) * f
where:
P_alv alveolar partial pressure of inert gas
P_amb ambient pressure
P_H2O water vapour partial pressure = ~0.0627 bar
P_CO2 carbon dioxide partial pressure = ~0.0534 bar
Rq respiratory quotient (O2 consumption / CO2 production)
f fraction of inert gas
In our calculations, we simplify this to use an effective water vapour pressure
WV = P_H20 - (1 - Rq) / Rq * P_CO2
Buhlmann ignored the contribution of CO2 (i.e. Rq = 1.0), whereas Schreiner
adopted Rq = 0.8.
WV_Buhlmann = PP_H2O = 0.0627 bar
WV_Schreiner = 0.0627 - (1 - 0.8) / Rq * 0.0534 = 0.0493 bar
Buhlmann calculations use the Buhlmann value, VPM-B calculations use the
Schreiner value.
Concept explained here:
http://www.divetable.de/workshop/V1_e.htm
Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
In other implementations of VPM-B, surface_tension_gamma and
skin_compression_gammaC are taken as 0.0179 N/msw and 0.257 N/msw respectively.
We do pressure calculations in bar, not msw, so our gamma values need to reflect
that. Previously we had used 0.179 and 2.57, which are close but not quite
correct (10 msw == 1.01325 bar).
Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
The pressure for the Boyle compensation is of the first ceiling,
i.e. the ceiling seen from the bottom rather than the first
stop.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Otherwise, the results of the calculations tend to be rather
random and irreproducible...
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
this does not increas binary size increadably but is usefull
when trying to figure out what the planner is doing.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This uses a bit of algebra to simplify the formula for Boyle's law
correction and introduces another algebraic cubic root solver that
can also deal with negative discriminants thanks to a trigonometric
formula from Wikipedia.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
There is nothing to compensate but we would hit a 0/0 numerical
instability there.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
otherwise VPM-B planned profiles seem to violate the ceiling. This needs
the first_stop_pressure to be available also in the profile, so I made
it global in planner.c
Important lesson: If you want to use deco_allowed_depth on a tissue_tolerance
that comes from a VPM-B planned dive, you have to call boyles_law() before
add_segment()!
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
I have no idea how these could have been left behind
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
The default value for critical_volume_lambda is 6500 fsw.min (= 199.58 bar.min)
for VPM-B, rather than 7500 fsw.min (= 230.284 bar.min) for VPM. This is
consistent with V-Planner, MultiDeco, GUE DecoPlanner, HLPlanner and the
comments in the Fortran code explanation.
Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Since a8ce8, that made deco_allowed_depth work for VPM-B as well, this
function became obsolete but was reintroduced by one of Jan's latest patches.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This patch is purely cosmetic except for the fact it changes the
critical radii to the V-planner with Boyle compensation values.
These values would have been set anyway by Jan's commit
"VPM-B: Set radius constants to values reccomended by V-Planner" which
will conflict with this anyway. This way, the last chunk of Jan's patch
can just be discarded.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
We can use the analytic solution of a cubic in two different places.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This patch makes deco_allowed_depth() work both for Buehlmann as well as
VPM-B (as long as the VPM-B internal variable total_gradient[] is valid).
As a bonus, in VPM-B mode, in the planner, the ceilings are VPM-B ceilings
and not Buehlmann GF.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
V-Planner reccomends smaller values for the VPM with the Boyles
compensation. Also missing units comments were added.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
Now, we calculate the volume of free gas not only based on the deco
time but also time on the surface, needed for the full desaturation.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
This is a very basic implementation that uses bin search for solving the cubic.
It's not called anywhere at this stage, needs to be changed to analytic solution.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
Include units in the comments of VPM structure definition. We should
confirm the units surface_tension_gamma and skin_compression_gammaC.
Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Adopt the same critical radii used by Eric Baker's original VPM Fortran
code and V-Planner.
Standard critical volume lambda = 7500 fsw-min (numerous sources). We need
to convert it properly.
λ = 7500 fsw-min
= 7500/33 = 227.2727 ata-min
= 227.2727 * 1.01325 bar-min
= 230.284 bar-min
Signed-off-by: Rick Walsh <rickmwalsh@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
It improves (increases) gradients for all the compartments,
so more free gas can be created in the divers body. Next gradients
will converge, so the volume won't exceed the safe limit, indicated
by the crit_volume_lambda parameter.
Function takes time of the last deco in seconds.
Requires vpmb_start_gradient() to be run before.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
Check during the trial_ascent() if existing pressure gradient is
smaller than previously calculated max gradient. If not, ascent
is impossible from the vpm-b's point of view.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
Calculate the max difference between tissue saturation and ambient
pressure that can be accepted during the ascent.
Partial results are kept for later improving in next CVA iterations
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
This function calculates the size of nuclei at the end of deco,
then simulates their regeneration, to the moment before the deco.
This is redundant as nuclear regeneration is a very slow process.
Function should be called with time in seconds, just before the ascent.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
According to mathematica
In[4]:= f[x_] := x^3 - b x^2 - c
In[18]:= Solve[f[x] == 0, x]
Out[18]= {{x ->
1/3 (b + (
2^(1/3) b^2)/(2 b^3 + 27 c + 3 Sqrt[3] Sqrt[4 b^3 c + 27 c^2])^(
1/3) + (2 b^3 + 27 c + 3 Sqrt[3] Sqrt[4 b^3 c + 27 c^2])^(1/3)/
2^(1/3))}, {x ->
b/3 - ((1 + I Sqrt[3]) b^2)/(
3 2^(2/3) (2 b^3 + 27 c + 3 Sqrt[3] Sqrt[4 b^3 c + 27 c^2])^(
1/3)) - ((1 - I Sqrt[3]) (2 b^3 + 27 c +
3 Sqrt[3] Sqrt[4 b^3 c + 27 c^2])^(1/3))/(6 2^(1/3))}, {x ->
b/3 - ((1 - I Sqrt[3]) b^2)/(
3 2^(2/3) (2 b^3 + 27 c + 3 Sqrt[3] Sqrt[4 b^3 c + 27 c^2])^(
1/3)) - ((1 + I Sqrt[3]) (2 b^3 + 27 c +
3 Sqrt[3] Sqrt[4 b^3 c + 27 c^2])^(1/3))/(6 2^(1/3))}}
For the values of b and c encounterd in the algorithm, the first solution is in fact the
only real one that we are after. So we can use this solution instead of doing a binary
search for the root of the cubic.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
Add new structures holding vpm-b state.
Add function calculating current crushing pressure.
Call it from add_segment() on every ambient pressure change.
It determines what pressure acts on nuclei during the descent
and thus their size at the beggining of the deco.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
This function calculates the pressure inside the nucleon
during the impermeable phase.
In the original code, Newton's method is used, for simplicity, we
use binary search for finding cubic equations root.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
Created vpmb_config structure based on buehlmann_config.
Set it's default values to ones taken from the existing C implementation.
Signed-off-by: Jan Darowski <jan.darowski@gmail.com>
The ratio between SAC and oxygen metabolism rate can be assumed constant
but not the metabolism rate. So we better base our calculation on the ratio
that uses the SAC from the preferences as that pairs well with the O2
consumption from the preferences.
Hence we ran remove the sac parameter from fill_pressures().
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Calculations for passive semi-closed rebreathers are pretty much like OC
except the pO2 is lower bey a certain (SAC dependent) factor. This patch
introduces the corresponding calculations in case dctype == PSCR which is
so far never set and there is currently no UI for these calculations. As
pO2 is SAC dependent it takes a certain attempt at getting it and drops to
defaults from the prefs otherwise.
As there is no UI at this point and I also don't have any dives, this has
not received much testing, yet, but it compiles. At least.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
In the transition to the partial pressure helper function,
the water vapor component of the breathing gas had been dropped.
This had a significant effect on deco times for deep dives.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This patch responds to the side effects that the CCR code has had with
respect to ceilings in OC dives and dive plans. Dive ceilings are now
calculated correctly again.
The following were performed:
1) remove the oxygen sensor and setpoint fields from the gas_pressures
structure.
2) Re-insert setpoint and oxygen sensor fields in the plot_data structure.
3) Remove the algorithm that reads the o2 sensor data and calculates the
pressures.po2 value from function fill_pressures() in dive.c and save
it as a separate function calc_ccr_po2() in profile.c.
4) Activate calc_ccr_po2 from function fill_pressures() in profile.c.
5) Move the relative position of the call to fill_pressures() within the
function create_polt_info_new() in profile.c.
Signed-off-by: willem ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This patch does three things:
1) A new function fill_o2_values() is added to profile.c. This
fills all oxygen sesnsor and setpoint values that have been
zeroed before in order to save space in the dive log. This
recreates the full set of sensor values obtained from the
original CCR xml log file.
2) Function fill_o2_values() is activated in function create_
plot_info_new() in profile.c
3) The calling parameters to function fill_pressures() in dive.c
are changed. The last parameter is now a pointer to a structure
of divecomputer. This will be needed in the last patch of the
present series of three patches.
[Dirk Hohndel: minor whitespace cleanup]
Signed-off-by: willem ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This adds a toolbox icon to turn on a tissue plot inspired by the bar
graph of the Sherwater Petrel,
It shows the inert gas partial pressures for individual compartments. If
they are below the ambient pressure (grey line) they are shown in units of
the ambient pressure, if they are above, the excess is shown as a
percentage of the allowed overpressure for plain Buehlmann. So it has the
same units as a gradient factor. Thus also the a gradient factor line (for
the current depth) is shown.
The different tissues get different colors, greener for the faster ones and bluer
for the slower ones.
Positioning and on/off icon action still need some tender loving care.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This patch introduces a new structure holding partial pressures (doubles in bar) for
all three gases and a helper function to compute them from gasmix (which holds fractions)
and ambient pressure. Currentlty this works for OC and CCR, to be extended later to PSCR.
Currently the dive_comp_type argument is unused.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
In a dive, when you choose a very low GFlow (like 5 or 9) and a trimix
with quite some He (12/48 in the example) and descend fast, the ceiling
seems to do strange things in the first minutes of the dive (very very
deep for example or jumping around).
To understand what is going on we have to recall what gradient factors do
in detail: Plain Buehlmann gives you for each tissue a maximal inert gas
pressure that is a straight line when plotted against the ambient
pressure. So for each depth (=ambient pressure) there is a maximally
allowed over-pressure.
The idea of gradient factors is that one does not use all the possible
over-pressure that Buehlmann gives us but only a depth dependent fraction.
GFhigh is the fraction of the possible over-pressure at the surface while
GFlow is the fraction at the first deco stop. In between, the fraction is
linearly interpolated. As the Buehlmann over-pressure is increasing with
depth and typically also the allowed overpressure after applications of
gradient factors increases with depth or said differently: the tissue
saturation has to be lower if the diver wants to ascent.
The main problem is: What is the first stop (where to apply GFlow)? In a
planned dive, we could take the first deco stop, but in a real dive from a
dive computer download it is impossible to say what constitutes a stop and
what is only a slow ascent?
What I have used so far is not exactly the first stop but rather the first
theoretical stop: During all of the dive, I have calculated the ceiling
under the assumption that GFlow applies everywhere (and not just at a
single depth). The deepest of these ceilings I have used as the “first
stop depth”, the depth at which GFlow applies.
Even more, I only wanted to use the information that a diver has during
the dive, so I actually only considered the ceilings in the past (and not
in the future of a given sample).
But this brings with it the problem that early in the dive, in particular
during the descent the lowest ceiling so far is very shallow (as not much
gas has built up in the body so far).
This problem now interferes with a second one: If at the start of the dive
when the all compartments have 790mbar N2 the diver starts breathing a
He-heavy mix (like 12/48) and descents fast the He builds up in the
tissues before the N2 can diffuse out. So right at the start, we already
encounter high tissue loadings.
If now we have a large difference between GFhigh and GFlow but they apply
at very similar depth (the surface and a very shallow depth of the deepest
ceiling (which for a non-decompression dive would be theoretically at
negative depth) so far) it can happen that the linear interpolation as
opposite slope then in the typical case above: The allowed over-pressure
is degreasing with depth, shallower depth do not require lower gas loading
in the tissue (i.e. can be reached after further off-gasing) but but
tolerate higher loadings. In that situation the ceiling disappears (or is
rather a floor).
So far, I got rid of that problem, by stating that the minimum depth for
GFlow was 20m (after all, GFlow is about deep stops, so it should better
not be too shallow). Now the dive reported in ticket #549 takes values to
an extreme in such away that 20m (which is determined by
buehlmann_config.gf_low_position_min in deco.c) was not enough to prevent
this inversion problem (or in a milder form that the interpolation of
gradient factors is in fact an extrapolation with quite extreme values).
This patch that gets rid of the problem for the dive described above but
still it is possible to find (more extreme) parameter choices that lead to
non-realistic ceilings.
Let me close by pointing out that all this is only about the descent, as
it is about too shallow depth for GFlow. So no real deco (i.e. later part
of the dive) is inflicted. This is only about a theoretical ceiling
displayed possibly in the first minutes of a dive. So this is more an
aesthetically than a practical problem.
Fixes#549
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Lets just use pO₂ instead of PO2, ppO2, ppO₂, PO₂.
They all mean the same, but it's better to be
consistent
Signed-off-by: Henrik Brautaset Aronsen <subsurface@henrik.synth.no>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
I know everyone will hate it.
Go ahead. Complain. Call me names.
At least now things are consistent and reproducible.
If you want changes, have your complaint come with a patch to
scripts/whitespace.pl so that we can automate it.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
