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>
This re-organizes the saturation calculations to be in my opinion
clearer: we used to have the "one second" case completely separate from
the "generic interval" case, and this undoes that.
It *does* keep the special static cache for the one-second buehlmann
factors, and expands that with a *dynamic* cache for each tissue index
that contains the previous value of the buehlmann factor for a
particular duration.
The point is, usually we end up using some fixed duration, so the cache
hit ratio is quite high. And doing a memory load from a cache is *much*
faster than calculating exponentials.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Earlier we converted the C++ code to using true/false, and this converts
the C code to using the same style.
We already depended on stdbool.h in subsurfacestartup.[ch], and we build
with -std=gnu99 so nobody could build subsurface without a c99 compiler.
[Dirk Hohndel: small change suggested by Thiago Macieira: don't include
stdbool.h for C++]
Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
These adds some ifdef's around some debug functions to disable them when
not using them.
Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
I always worry if these are worth following up on - but these seem pretty
clear and obvious to me. As far as the planner is concerned, depth is
unsigned.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
- remove the build flags and libraries from the Makefile / Configure.mk
- remove the glib types (gboolean, gchar, gint64, gint)
- comment out / hack around gettext
- replace the glib file helper functions
- replace g_ascii_strtod
- replace g_build_filename
- use environment variables instead of g_get_home_dir() & g_get_user_name()
- comment out GPS string parsing (uses glib utf8 macros)
This needs massive cleanup, but it's a snapshot of what I have right now, in
case people want to look at it.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
I think that displaying tissue loadings either as pressure or as
percentages is not very intuitive but that it makes much more sense when
translated to ceiling depths.
This change enables just that for the 16 tissues in our calculated ceiling
and visualizes this in the profile graph.
There is a checkbox in the preferences to turn this on. If enabled, all
tissues having non-trivial ceilings are also shown in the info box.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
The biggest problem here was that bool has different sizes in C and C++
code. So using this in a structure shared between the two sides wasn't a
smart idea.
Instead I went with 'short', but that caused problems with Qt being to
smart for its own good and not doing the right thing when dealing with
'boolean' settings and a short value. This may be something in the way I
implemented things (as I doubt that something this fundamental would be
broken) but the workaround implemented here (explicitly using 0 or 1
depending on the value of the boolean) seems to work.
I also decided to get rid of the confusion of where gflow/gfhigh are
floating point (0..1) and when they are integers (0..100). We now use
integers anywhere outside of deco.c.
I also applied some serious spelling corrections to the preferences
dialog's ui file.
Finally, this enables the code that selects which partial pressure graph
to show.
Still to do: font size, metric/imperial logic
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
They do the "02=0 means air" thing autmatically, and make for less
typing. So use them more widely in places that looked up the o2 and he
permille values of a gasmix.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
There are two ways to look at surface pressure. One is to say "what was
the surface pressure during that dive?" - in that case we now return an
average over the pressure reported by the different divecomputers (or the
standard 1013mbar if none reported any).
Or you want to do specific calculations for a specific divecomputer - in
which case we access only the pressure reported by THAT divecomputer, if
present (and fall back to the previous case, otherwise).
We still have lots of places in Subsurface that only act on the first
divecomputer. As a side effect of this change we now make this more
obvious as we in those cases pass a pointer to the first divecomputer
explicitly to the calculations.
Either way, this commit should prevent us from ever mistakenly basing our
calculations on a surface pressure of 0 (which is the initial bug in
deco.c that triggered all this).
Similar changes need to be made for other elements that we currently only
use from the first divecomputer, i.e., salinity.
Reported-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
It wasn't really used. The only reader of that array was the same thing
that wrote the entry, so instead of storing it in the array (and never
using it ever after), just use the calculation directly, and remove the
array entirely.
This makes it much easier to see that the gradient factors are not used
for any long-term state. We use them only for the pressure tolerance
calculations at that particular point, and there is no "history"
associated with it.
This matters mainly because it means that we can do all the deco
initialization and setup without worrying about exactly which gradient
factors we will use. And we can use different gradient factors for
diving and planning and no-fly calculations without the GF choice
affecting the tissue state.
Acked-by: Robert C. Helling <helling@lmu.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
We'll want to use a 'static const' gasmix for the upcoming no-fly-time
code, so prepare for it by just marking the read-only gasmix argument as
'const'.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This moves some double/floating handling for po2 to plain integer. There
are still non int values around (also for phe and po2) in the plot area.
Signed-off-by: Jan Schubert <Jan.Schubert@GMX.li>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Mostly coding style and whitespace changes plus making lots of functions
static that have no need to be extern. This also helped find a bit of code
that is actually no longer used.
This should have absolutely no functional impact - all changes should be
purely cosmetic. But it removes a bunch of lines of code and makes the
rest easier to read.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This moves the fields 'duration', 'surfacetime', 'maxdepth',
'meandepth', 'airtemp', 'watertemp', 'salinity' and 'surface_pressure'
to the per-divecomputer data structure. They are filled in by the dive
computer, and normally not edited.
NOTE! All actual *use* of this data was then changed from dive->field to
dive->dc.field programmatically with a shell-script and sed, and the
result then edited for details. So while the XML save and restore code
has been updated, all the displaying etc will currently always just show
the first dive computer entry.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This patch centralizes the definition for surface pressure, oxygen in
air, (re)defines all such values as plain integers and adapts calculations.
It eliminates 11 (!) occurrences of definitions for surface pressure and
also a few for oxygen in air.
It also rewrites the calculation for EAD, END and EADD using the new
definitons, harmonizing it for OC and CC and fixes a bug for EADD OC
calculation.
And finally it removes the unneeded variable entry_ead in gtk-gui.c.
Jan
Signed-off-by: Jan Schubert <Jan.Schubert@GMX.li>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
- MOD: Maximum Operation Depth based on a configurable limit
- EAD: Equivalent Air Depth considering N2 and (!) O2 narcotic
- END: Equivalent Nitrogen (Narcotic) Depth considering just N2 narcotic
(ignoring O2)
- EADD: Equivalent Air Density Depth
Please note that some people and even diving organisations have opposite
definitions for EAD and END. Considering A stands for Air, lets choose the
above. And considering N for Nitrogen it also fits in this scheme.
This patch moves N2_IN_AIR from deco.c to dive.h as this is already used
in several places and might be useful for future use also. It also
respecifies N2_IN_AIR to a more correct value of 78,084%, the former one
also included all other gases than oxygen appearing in air. If someone
needs to use the former value it would be more correct to use 1-O2_IN_AIR
instead.
Signed-off-by: Jan Schubert / Jan.Schubert@GMX.li
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This moves the point where GF_low applies up which implies that at all
shallower depth (i.e. during deco) a lower GF results which makes the deco
longer compared to the previous implementation.
Of course, "GF_low" applies at first deco stop is a bit tricky since the
depth of the first deco stop again depends on GF_low, i.e. there is
another equation to solve. You can do this by inverting the equation for
the ambient pressure and use GF_low as the gradient factor. This yields
amb = (b * M_value_corrected - GF_low * a * b) / ((1-b) * GF_low + b)
Signed-off-by: Robert C. Helling helling@atdotde.de
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
In commit d163a68ac69e "Clean up the rewritten deco.c" I apparently made
one more change than I intended - I changed the last deco stop back to 3m
instead of allowing the smooth mode to go all the way back to 0 without
any discrete steps.
This fixes that mistake.
Reported-by: Robert C. Helling <helling@lmu.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
In commit a7902f279a57 "Rewrite of the deco code" Robert kept the old code
that he replaced around; I removed all that as it's in the git history if
we ever need to look at it again but doesn't really help us in the file as
it is.
I also removed constants, variables and config parameters that aren't used
in the new implementation and did some coding style / formatting changes
to make deco.c more consistent with the rest of Subsurface. I also updated
the comments at the top of the file to reflect reality.
I did one change that actually affects the code. In the explanation of his
changes Robert said that gf_low_pressure_this_dive is initialized to the
exquivalent of 20m, yet his code added the surface pressure twice. I
decided to change the default config value from 3 (bar) to 2 so that this
indeed reflects (about) 20m (as in the code below surface_pressure is
added to this value).
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
o) Instead of using gradient factors as means of comparison, I now use
pressure (as in: maximal ambient pressure).
o) tissue_tolerance_calc() now computes the maximal ambient pressure now
respecting gradient factors. For this, it needs to know about the
surface pressure (as refernce for GF_high), thus gets *dive as an
argument. It is called from add_segment() which this also needs *dive
as an additional argument.
o) This implies deco_allowed_depth is now mainly a ambient-pressure to
depth conversion with decorations to avoid negative depth (i.e. no deco
obliation), implementation of quantization (!smooth => multiples of 3m)
and explicit setting of last deco depth (e.g. 6m for O2 deco).
o) gf_low_pressure_this_dive (slight change of name), the max depth in
pressure units is updated in add_segment. I set the minimal value in
buehlmann_config to the equivalent of 20m as otherwise good values of
GF_low add a lot of deco to shallow dives which do not need deep stops
in the first place.
o) The bogus loop is gone as well as actual_gradient_limit() and
gradient_factor_calculation() and large parts of deco_allowed_depth()
although I did not delete the code but put it in comments.
o) The meat is in the formula in lines 147-154 of deco.c. Here is the
rationale:
Without gradient factors, the M-value (i.e the maximal tissue pressure)
at a given depth is given by ambient_pressure / buehlmann_b + a.
According to "Clearing Up The Confusion About "Deep Stops" by Erik C.
Baker (as found via google) the effect of the gradient factors is no
replace this by a reduced affine relation (i.e. another line) such that
at the surface the difference between M-value and ambient pressure is
reduced by a factor GF_high and at the maximal depth by a factor
GF_low.
That is, we are looking for parameters alpha and beta such that
alpha surface + beta = surface + gf_high * (surface/b + a - surface)
and
alpha max_p + beta = max_p + gf_low * (max_p/b + a - max_p)
This can be solved for alpha and beta and then inverted to obtain the
max ambient pressure given tissue loadings. The result is the above
mentioned formula.
Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This appears to happen if we have impossible dive sequences in the
dive_list (i.e., merging XML files from two different divers with
overlapping trips).
We need to fix the underlying cause for this issue (i.e., only pick the
'right' dives to calculate the residual tissue saturation), but at least
this code prevents the hang in an infinite loop.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
We kept reduing all the deco calculations, including the previous dives
(if any) for each segment we add to the dive plan. This simply remembers
the last stage and then just adds to that.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
The ceiling calculations for the gradient factors still had a 3m increment
hardcoded. This is now also conditional on the smooth parameter.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
The old implementation was broken in several ways.
For one thing the GF values are percentages, so they should normally be
0 < GF < 1 (well, some crazy people like to go above that).
With this most of the Bühlmann config constants were wrong.
Furthermore, after we adjust the pressure tolerance based on the gradient
factors, we need to convert this back into a depth (instead of passing
back the unmodified depth - oops).
Finally, this commit adds closed circuit support to the deco calculations.
Major progress and much more useful at this stage.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
There are a couple of issues with this commit:
GtkEntry should emit the 'changed' signal when it is modified (so that
changes in the preferences get applied right away) - but that doesn't
appear to be working consistently.
Also, this doesn't appear to affect the deco of any dives that I try it
with. So my guess is something is wrong with the underlying deco
algorithm. That's diappointing.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This also initializes the N2 tissue saturations to correct numbers
(setting them to zero was clearly silly).
With this commit we walk back in the dive_table until we find a surface
intervall that's longer than 48h. Or a dive that comes after the last one
we looked at; that would indicate that this is a divelist that contains
dives from multiple divers or dives that for other reasons are not
ordered. In a sane environment one would assume that the dives that need
to be taken into account when doing deco calculations are organized as one
trip in the XML file and so this logic should work.
One major downside of the current implementation is that we recalculate
everything whenever the plot_info is recreated - which happens quite
frequently, for example when resizing the window or even when we go into
loup mode. While this isn't all that compute intensive, this is an utter
waste and we should at least cache the saturation inherited from previous
dives (and clear that number when the selected dive changes). We don't
want to cache all of it as the recreation of the plot_info may be
triggered by the user changing equipment (and most importantly, gasmix)
information. In that case the deco data for this dive does indeed have to
be recreated. But without changing the current dive the saturation after
the last surface intervall should stay the same.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Usually dive computers show the ceiling in terms of the next deco stop -
and those are in 3m increments. This commit also adds the ability to chose
either the typical 3m increments or the smooth ceiling that the Bühlmann
algorithm actually calculates.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
