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Clean up the rewritten deco.c

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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>
This commit is contained in:
Dirk Hohndel 2013-01-08 09:29:07 -08:00
parent 67d59ff018
commit fc8b37d86b
1 changed files with 24 additions and 103 deletions
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127
deco.c
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@ -1,18 +1,19 @@
/* calculate deco values /* calculate deco values
* based on Bühlmann ZHL-16b * based on Bühlmann ZHL-16b
* based on an implemention by heinrichs weikamp for the DR5 * based on an implemention by heinrichs weikamp for the DR5
* the original file doesn't carry a license and is used here with * the original file was given to Subsurface under the GPLv2
* the permission of Matthias Heinrichs * by Matthias Heinrichs
* *
* The implementation below is (C) Dirk Hohndel 2012 and released under the GPLv2 * The implementation below is a fairly complete rewrite since then
* (C) Robert C. Helling 2013 and released under the GPLv2
* *
* clear_deco() - call to initialize for a new deco calculation * add_segment() - add <seconds> at the given pressure, breathing gasmix
* add_segment(pressure, gasmix, seconds) - add <seconds> at the given pressure, breathing gasmix * deco_allowed_depth() - ceiling based on lead tissue, surface pressure, 3m increments or smooth
* deco_allowed_depth(tissues_tolerance, surface_pressure, dive, smooth) * set_gf() - set Buehlmann gradient factors
* - ceiling based on lead tissue, surface pressure, 3m increments or smooth * clear_deco()
* set_gf(gflow, gfhigh) - set Buehlmann gradient factors * cache_deco_state()
* void cache_deco_state(tissue_tolerance, char **datap) - cache the relevant data allocate memory if needed * restore_deco_state()
* double restore_deco_state(char *data) - restore the state and return the tissue_tolerance * dump_tissues()
*/ */
#include <math.h> #include <math.h>
#include <string.h> #include <string.h>
@ -22,16 +23,12 @@
struct buehlmann_config { struct buehlmann_config {
double satmult; //! safety at inert gas accumulation as percentage of effect (more than 100). double satmult; //! safety at inert gas accumulation as percentage of effect (more than 100).
double desatmult; //! safety at inert gas depletion as percentage of effect (less than 100). double desatmult; //! safety at inert gas depletion as percentage of effect (less than 100).
double safety_dist_deco_stop;//! assumed distance to official decompression where decompression takes places.
int last_deco_stop_in_mtr; //! depth of last_deco_stop. int last_deco_stop_in_mtr; //! depth of last_deco_stop.
double gf_high; //! gradient factor high (at surface). double gf_high; //! gradient factor high (at surface).
double gf_low; //! gradient factor low (at bottom/start of deco calculation). double gf_low; //! gradient factor low (at bottom/start of deco calculation).
double gf_low_position_min; //! gf_low_position below surface_min_shallow. double gf_low_position_min; //! gf_low_position below surface_min_shallow.
double gf_low_position_max; //! gf_low_position below surface_max_depth.
double gf_high_emergency; //! emergency gf factors
double gf_low_emergency; //! gradient factor low (at bottom/start of deco calculation).
}; };
struct buehlmann_config buehlmann_config = { 1.0, 1.01, 0.5, 0, 0.75, 0.35, 3.0, 6.0, 0.95, 0.95 }; struct buehlmann_config buehlmann_config = { 1.0, 1.01, 3, 0.75, 0.35, 2.0 };
struct dive_data { struct dive_data {
double pressure; //! pesent ambient pressure double pressure; //! pesent ambient pressure
double surface; //! pressure at water surface double surface; //! pressure at water surface
@ -82,10 +79,6 @@ const double buehlmann_He_factor_expositon_one_second[] = {
#define WV_PRESSURE 0.0627 /* water vapor pressure */ #define WV_PRESSURE 0.0627 /* water vapor pressure */
#define N2_IN_AIR 0.7902 #define N2_IN_AIR 0.7902
#define DIST_FROM_3_MTR 0.28
#define PRESSURE_CHANGE_3M 0.3
#define TOLERANCE 0.02
#define DECO_STOPS_MULTIPLIER_MM 3000.0 #define DECO_STOPS_MULTIPLIER_MM 3000.0
double tissue_n2_sat[16]; double tissue_n2_sat[16];
@ -95,38 +88,6 @@ int ci_pointing_to_guiding_tissue;
double gf_low_pressure_this_dive; double gf_low_pressure_this_dive;
#define TISSUE_ARRAY_SZ sizeof(tissue_n2_sat) #define TISSUE_ARRAY_SZ sizeof(tissue_n2_sat)
/* static double actual_gradient_limit_obsolete(const struct dive_data *data) */
/* { */
/* double pressure_diff, limit_at_position; */
/* double gf_high = buehlmann_config.gf_high; */
/* double gf_low = buehlmann_config.gf_low; */
/* pressure_diff = data->pressure - data->surface; */
/* if (pressure_diff > TOLERANCE) { */
/* if (pressure_diff < gf_low_position_this_dive) */
/* limit_at_position = gf_high - ((gf_high - gf_low) * pressure_diff / gf_low_position_this_dive); */
/* else */
/* limit_at_position = gf_low; */
/* } else { */
/* limit_at_position = gf_high; */
/* } */
/* return limit_at_position; */
/* } */
/* static double gradient_factor_calculation_obsolete(const struct dive_data *data) */
/* { */
/* double tissue_inertgas_saturation; */
/* tissue_inertgas_saturation = tissue_n2_sat[ci_pointing_to_guiding_tissue] + */
/* tissue_he_sat[ci_pointing_to_guiding_tissue]; */
/* if (tissue_inertgas_saturation < data->pressure) */
/* return 0.0; */
/* else */
/* return (tissue_inertgas_saturation - data->pressure) / */
/* (tissue_inertgas_saturation - tissue_tolerated_ambient_pressure[ci_pointing_to_guiding_tissue]); */
/* } */
static double tissue_tolerance_calc(const struct dive *dive) static double tissue_tolerance_calc(const struct dive *dive)
{ {
int ci = -1; int ci = -1;
@ -144,13 +105,12 @@ static double tissue_tolerance_calc(const struct dive *dive)
/* tissue_tolerated_ambient_pressure[ci] = (tissue_inertgas_saturation - buehlmann_inertgas_a) * buehlmann_inertgas_b; */ /* tissue_tolerated_ambient_pressure[ci] = (tissue_inertgas_saturation - buehlmann_inertgas_a) * buehlmann_inertgas_b; */
tissue_tolerated_ambient_pressure[ci] = (-buehlmann_inertgas_a * buehlmann_inertgas_b * (gf_high * gf_low_pressure_this_dive - gf_low * surface) tissue_tolerated_ambient_pressure[ci] = (-buehlmann_inertgas_a * buehlmann_inertgas_b * (gf_high * gf_low_pressure_this_dive - gf_low * surface) -
- (1.0 - buehlmann_inertgas_b) * (gf_high - gf_low) * gf_low_pressure_this_dive * surface (1.0 - buehlmann_inertgas_b) * (gf_high - gf_low) * gf_low_pressure_this_dive * surface +
+ buehlmann_inertgas_b * (gf_low_pressure_this_dive - surface) * tissue_inertgas_saturation) buehlmann_inertgas_b * (gf_low_pressure_this_dive - surface) * tissue_inertgas_saturation) /
/ (-buehlmann_inertgas_a * buehlmann_inertgas_b * (gf_high - gf_low) +
(-buehlmann_inertgas_a * buehlmann_inertgas_b * (gf_high - gf_low) (1.0 - buehlmann_inertgas_b)*(gf_low * gf_low_pressure_this_dive - gf_high * surface) +
+ (1.0 - buehlmann_inertgas_b)*(gf_low * gf_low_pressure_this_dive - gf_high * surface) buehlmann_inertgas_b * (gf_low_pressure_this_dive - surface));
+ buehlmann_inertgas_b * (gf_low_pressure_this_dive - surface));
if (tissue_tolerated_ambient_pressure[ci] > ret_tolerance_limit_ambient_pressure) if (tissue_tolerated_ambient_pressure[ci] > ret_tolerance_limit_ambient_pressure)
{ {
@ -161,7 +121,7 @@ static double tissue_tolerance_calc(const struct dive *dive)
return ret_tolerance_limit_ambient_pressure; return ret_tolerance_limit_ambient_pressure;
} }
/* add a second at the given pressure and gas to the deco calculation */ /* add period_in_seconds at the given pressure and gas to the deco calculation */
double add_segment(double pressure, struct gasmix *gasmix, int period_in_seconds, double ccpo2, const struct dive *dive) double add_segment(double pressure, struct gasmix *gasmix, int period_in_seconds, double ccpo2, const struct dive *dive)
{ {
int ci; int ci;
@ -239,7 +199,7 @@ void clear_deco(double surface_pressure)
tissue_he_sat[ci] = 0.0; tissue_he_sat[ci] = 0.0;
tissue_tolerated_ambient_pressure[ci] = 0.0; tissue_tolerated_ambient_pressure[ci] = 0.0;
} }
gf_low_pressure_this_dive = surface_pressure+ buehlmann_config.gf_low_position_min; gf_low_pressure_this_dive = surface_pressure + buehlmann_config.gf_low_position_min;
} }
void cache_deco_state(double tissue_tolerance, char **cached_datap) void cache_deco_state(double tissue_tolerance, char **cached_datap)
@ -287,59 +247,20 @@ unsigned int deco_allowed_depth(double tissues_tolerance, double surface_pressur
unsigned int depth; unsigned int depth;
double pressure_delta; double pressure_delta;
pressure_delta = tissues_tolerance > surface_pressure ? tissues_tolerance - surface_pressure : 0.0; /* Avoid negative depths */ /* Avoid negative depths */
pressure_delta = tissues_tolerance > surface_pressure ? tissues_tolerance - surface_pressure : 0.0;
/* gboolean below_gradient_limit; */
/* double new_gradient_factor; */
/* double pressure_delta = tissues_tolerance - surface_pressure; */
/* struct dive_data mydata; */
/* int bail = 1000; */
/* if (pressure_delta > 0) { */
/* if (!smooth) { */
/* multiples_of_3m = (pressure_delta + DIST_FROM_3_MTR) / 0.3; */
/* depth = 3000 * multiples_of_3m; */
/* } else { */
/* depth = rel_mbar_to_depth(pressure_delta * 1000, dive); */
/* } */
/* } else { */
/* depth = 0; */
/* } */
/* mydata.pressure = depth_to_mbar(depth, dive) / 1000.0; */
/* mydata.surface = surface_pressure; */
/* new_gradient_factor = gradient_factor_calculation(&mydata); */
/* below_gradient_limit = (new_gradient_factor < actual_gradient_limit(&mydata)); */
/* while(!below_gradient_limit) */
/* { */
/* /\* we run into bugs where this turns into an infinite loop; so add */
/* * some bailout code that prints a warning but prevents the code from hanging *\/ */
/* if (--bail == 0) { */
/* printf("WARNING!!!\n==========\nThe deco_allowed_depth() loop appears to hang.\nBailing out.\n"); */
/* break; */
/* } */
/* if (!smooth) */
/* mydata.pressure += PRESSURE_CHANGE_3M; */
/* else */
/* mydata.pressure += PRESSURE_CHANGE_3M / 30; /\* 4in / 10cm instead *\/ */
/* new_gradient_factor = gradient_factor_calculation(&mydata); */
/* below_gradient_limit = (new_gradient_factor < actual_gradient_limit(&mydata)); */
/* } */
/* depth = rel_mbar_to_depth((mydata.pressure - surface_pressure) * 1000, dive); */
depth = rel_mbar_to_depth(pressure_delta * 1000, dive); depth = rel_mbar_to_depth(pressure_delta * 1000, dive);
if(!smooth) if(!smooth)
depth = ceil(depth / DECO_STOPS_MULTIPLIER_MM) * DECO_STOPS_MULTIPLIER_MM; depth = ceil(depth / DECO_STOPS_MULTIPLIER_MM) * DECO_STOPS_MULTIPLIER_MM;
if(depth > 0 && depth < buehlmann_config.last_deco_stop_in_mtr * 1000) if(depth > 0 && depth < buehlmann_config.last_deco_stop_in_mtr * 1000)
depth = buehlmann_config.last_deco_stop_in_mtr * 1000; depth = buehlmann_config.last_deco_stop_in_mtr * 1000;
return depth; return depth;
} }
void set_gf(double gflow, double gfhigh) void set_gf(double gflow, double gfhigh)
{ {
if (gflow != -1.0) if (gflow != -1.0)