subsurface/core/gaspressures.c
Berthold Stoeger 39ede7e9e8 Cleanup: introduce function to set pressure values
Instead of assigning the the lvalue of the SENSOR_PRESSURE
macro, introduce a general function to set pressure values.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
2019-07-18 05:50:22 -07:00

488 lines
15 KiB
C

// SPDX-License-Identifier: GPL-2.0
/* gaspressures.c
* ---------------
* This file contains the routines to calculate the gas pressures in the cylinders.
* The functions below support the code in profile.c.
* The high-level function is populate_pressure_information(), called by function
* create_plot_info_new() in profile.c. The other functions below are, in turn,
* called by populate_pressure_information(). The calling sequence is as follows:
*
* populate_pressure_information() -> calc_pressure_time()
* -> fill_missing_tank_pressures() -> fill_missing_segment_pressures()
* -> get_pr_interpolate_data()
*
* The pr_track_t related functions below implement a linked list that is used by
* the majority of the functions below. The linked list covers a part of the dive profile
* for which there are no cylinder pressure data. Each element in the linked list
* represents a segment between two consecutive points on the dive profile.
* pr_track_t is defined in gaspressures.h
*/
#include "ssrf.h"
#include "dive.h"
#include "display.h"
#include "profile.h"
#include "gaspressures.h"
#include "pref.h"
/*
* simple structure to track the beginning and end tank pressure as
* well as the integral of depth over time spent while we have no
* pressure reading from the tank */
typedef struct pr_track_struct pr_track_t;
struct pr_track_struct {
int start;
int end;
int t_start;
int t_end;
int pressure_time;
pr_track_t *next;
};
typedef struct pr_interpolate_struct pr_interpolate_t;
struct pr_interpolate_struct {
int start;
int end;
int pressure_time;
int acc_pressure_time;
};
enum interpolation_strategy {SAC, TIME, CONSTANT};
static pr_track_t *pr_track_alloc(int start, int t_start)
{
pr_track_t *pt = malloc(sizeof(pr_track_t));
pt->start = start;
pt->end = 0;
pt->t_start = pt->t_end = t_start;
pt->pressure_time = 0;
pt->next = NULL;
return pt;
}
/* poor man's linked list */
static pr_track_t *list_last(pr_track_t *list)
{
pr_track_t *tail = list;
if (!tail)
return NULL;
while (tail->next) {
tail = tail->next;
}
return tail;
}
static pr_track_t *list_add(pr_track_t *list, pr_track_t *element)
{
pr_track_t *tail = list_last(list);
if (!tail)
return element;
tail->next = element;
return list;
}
static void list_free(pr_track_t *list)
{
if (!list)
return;
list_free(list->next);
free(list);
}
#ifdef DEBUG_PR_TRACK
static void dump_pr_track(int cyl, pr_track_t *track_pr)
{
pr_track_t *list;
printf("cyl%d:\n", cyl);
list = track_pr;
while (list) {
printf(" start %d end %d t_start %d:%02d t_end %d:%02d pt %d\n",
mbar_to_PSI(list->start),
mbar_to_PSI(list->end),
FRACTION(list->t_start, 60),
FRACTION(list->t_end, 60),
list->pressure_time);
list = list->next;
}
}
#endif
/*
* This looks at the pressures for one cylinder, and
* calculates any missing beginning/end pressures for
* each segment by taking the over-all SAC-rate into
* account for that cylinder.
*
* NOTE! Many segments have full pressure information
* (both beginning and ending pressure). But if we have
* switched away from a cylinder, we will have the
* beginning pressure for the first segment with a
* missing end pressure. We may then have one or more
* segments without beginning or end pressures, until
* we finally have a segment with an end pressure.
*
* We want to spread out the pressure over these missing
* segments according to how big of a time_pressure area
* they have.
*/
static void fill_missing_segment_pressures(pr_track_t *list, enum interpolation_strategy strategy)
{
double magic;
while (list) {
int start = list->start, end;
pr_track_t *tmp = list;
int pt_sum = 0, pt = 0;
for (;;) {
pt_sum += tmp->pressure_time;
end = tmp->end;
if (end)
break;
end = start;
if (!tmp->next)
break;
tmp = tmp->next;
}
if (!start)
start = end;
/*
* Now 'start' and 'end' contain the pressure values
* for the set of segments described by 'list'..'tmp'.
* pt_sum is the sum of all the pressure-times of the
* segments.
*
* Now dole out the pressures relative to pressure-time.
*/
list->start = start;
tmp->end = end;
switch (strategy) {
case SAC:
for (;;) {
int pressure;
pt += list->pressure_time;
pressure = start;
if (pt_sum)
pressure -= lrint((start - end) * (double)pt / pt_sum);
list->end = pressure;
if (list == tmp)
break;
list = list->next;
list->start = pressure;
}
break;
case TIME:
if (list->t_end && (tmp->t_start - tmp->t_end)) {
magic = (list->t_start - tmp->t_end) / (tmp->t_start - tmp->t_end);
list->end = lrint(start - (start - end) * magic);
} else {
list->end = start;
}
break;
case CONSTANT:
list->end = start;
}
/* Ok, we've done that set of segments */
list = list->next;
}
}
#ifdef DEBUG_PR_INTERPOLATE
void dump_pr_interpolate(int i, pr_interpolate_t interpolate_pr)
{
printf("Interpolate for entry %d: start %d - end %d - pt %d - acc_pt %d\n", i,
interpolate_pr.start, interpolate_pr.end, interpolate_pr.pressure_time, interpolate_pr.acc_pressure_time);
}
#endif
static struct pr_interpolate_struct get_pr_interpolate_data(pr_track_t *segment, struct plot_info *pi, int cur)
{ // cur = index to pi->entry corresponding to t_end of segment;
struct pr_interpolate_struct interpolate;
int i;
struct plot_data *entry;
interpolate.start = segment->start;
interpolate.end = segment->end;
interpolate.acc_pressure_time = 0;
interpolate.pressure_time = 0;
for (i = 0; i < pi->nr; i++) {
entry = pi->entry + i;
if (entry->sec < segment->t_start)
continue;
interpolate.pressure_time += entry->pressure_time;
if (entry->sec >= segment->t_end)
break;
if (i <= cur)
interpolate.acc_pressure_time += entry->pressure_time;
}
return interpolate;
}
static void fill_missing_tank_pressures(struct dive *dive, struct plot_info *pi, pr_track_t *track_pr, int cyl)
{
int i;
struct plot_data *entry;
pr_interpolate_t interpolate = { 0, 0, 0, 0 };
pr_track_t *last_segment = NULL;
int cur_pr;
enum interpolation_strategy strategy;
/* no segment where this cylinder is used */
if (!track_pr)
return;
if (dive->cylinder[cyl].cylinder_use == OC_GAS)
strategy = SAC;
else
strategy = TIME;
fill_missing_segment_pressures(track_pr, strategy); // Interpolate the missing tank pressure values ..
cur_pr = track_pr->start; // in the pr_track_t lists of structures
// and keep the starting pressure for each cylinder.
#ifdef DEBUG_PR_TRACK
dump_pr_track(cyl, track_pr);
#endif
/* Transfer interpolated cylinder pressures from pr_track strucktures to plotdata
* Go down the list of tank pressures in plot_info. Align them with the start &
* end times of each profile segment represented by a pr_track_t structure. Get
* the accumulated pressure_depths from the pr_track_t structures and then
* interpolate the pressure where these do not exist in the plot_info pressure
* variables. Pressure values are transferred from the pr_track_t structures
* to the plot_info structure, allowing us to plot the tank pressure.
*
* The first two pi structures are "fillers", but in case we don't have a sample
* at time 0 we need to process the second of them here, therefore i=1 */
for (i = 1; i < pi->nr; i++) { // For each point on the profile:
double magic;
pr_track_t *segment;
int pressure;
int *save_pressure, *save_interpolated;
entry = pi->entry + i;
save_pressure = &(entry->pressure[cyl][SENSOR_PR]);
save_interpolated = &(entry->pressure[cyl][INTERPOLATED_PR]);
pressure = *save_pressure ? *save_pressure : *save_interpolated;
if (pressure) { // If there is a valid pressure value,
last_segment = NULL; // get rid of interpolation data,
cur_pr = pressure; // set current pressure
continue; // and skip to next point.
}
// If there is NO valid pressure value..
// Find the pressure segment corresponding to this entry..
segment = track_pr;
while (segment && segment->t_end < entry->sec) // Find the track_pr with end time..
segment = segment->next; // ..that matches the plot_info time (entry->sec)
// After last segment? All done.
if (!segment)
break;
// Before first segment, or between segments.. Go on, no interpolation.
if (segment->t_start > entry->sec)
continue;
if (!segment->pressure_time) { // Empty segment?
*save_pressure = cur_pr; // Just use our current pressure
continue; // and skip to next point.
}
// If there is a valid segment but no tank pressure ..
if (segment == last_segment) {
interpolate.acc_pressure_time += entry->pressure_time;
} else {
// Set up an interpolation structure
interpolate = get_pr_interpolate_data(segment, pi, i);
last_segment = segment;
}
if(dive->cylinder[cyl].cylinder_use == OC_GAS) {
/* if this segment has pressure_time, then calculate a new interpolated pressure */
if (interpolate.pressure_time) {
/* Overall pressure change over total pressure-time for this segment*/
magic = (interpolate.end - interpolate.start) / (double)interpolate.pressure_time;
/* Use that overall pressure change to update the current pressure */
cur_pr = lrint(interpolate.start + magic * interpolate.acc_pressure_time);
}
} else {
magic = (interpolate.end - interpolate.start) / (segment->t_end - segment->t_start);
cur_pr = lrint(segment->start + magic * (entry->sec - segment->t_start));
}
*save_interpolated = cur_pr; // and store the interpolated data in plot_info
}
}
/*
* What's the pressure-time between two plot data entries?
* We're calculating the integral of pressure over time by
* adding these up.
*
* The units won't matter as long as everybody agrees about
* them, since they'll cancel out - we use this to calculate
* a constant SAC-rate-equivalent, but we only use it to
* scale pressures, so it ends up being a unitless scaling
* factor.
*/
static inline int calc_pressure_time(struct dive *dive, struct plot_data *a, struct plot_data *b)
{
int time = b->sec - a->sec;
int depth = (a->depth + b->depth) / 2;
if (depth <= SURFACE_THRESHOLD)
return 0;
return depth_to_mbar(depth, dive) * time;
}
#ifdef PRINT_PRESSURES_DEBUG
// A CCR debugging tool that prints the gas pressures in cylinder 0 and in the diluent cylinder, used in populate_pressure_information():
static void debug_print_pressures(struct plot_info *pi)
{
int i;
for (i = 0; i < pi->nr; i++) {
struct plot_data *entry = pi->entry + i;
printf("%5d |%9d | %9d |\n", i, get_plot_sensor_pressure(entry), get_plot_interpolated_pressure(entry));
}
}
#endif
/* This function goes through the list of tank pressures, of structure plot_info for the dive profile where each
* item in the list corresponds to one point (node) of the profile. It finds values for which there are no tank
* pressures (pressure==0). For each missing item (node) of tank pressure it creates a pr_track_alloc structure
* that represents a segment on the dive profile and that contains tank pressures. There is a linked list of
* pr_track_alloc structures for each cylinder. These pr_track_alloc structures ultimately allow for filling
* the missing tank pressure values on the dive profile using the depth_pressure of the dive. To do this, it
* calculates the summed pressure-time value for the duration of the dive and stores these * in the pr_track_alloc
* structures. This function is called by create_plot_info_new() in profile.c
*/
void populate_pressure_information(struct dive *dive, struct divecomputer *dc, struct plot_info *pi, int sensor)
{
UNUSED(dc);
int first, last, cyl;
cylinder_t *cylinder = dive->cylinder + sensor;
pr_track_t *track = NULL;
pr_track_t *current = NULL;
const struct event *ev, *b_ev;
int missing_pr = 0, dense = 1;
enum divemode_t dmode = dc->divemode;
const double gasfactor[5] = {1.0, 0.0, prefs.pscr_ratio/1000.0, 1.0, 1.0 };
/* if we have no pressure data whatsoever, this is pointless, so let's just return */
if (!cylinder->start.mbar && !cylinder->end.mbar &&
!cylinder->sample_start.mbar && !cylinder->sample_end.mbar)
return;
/* Get a rough range of where we have any pressures at all */
first = last = -1;
for (int i = 0; i < pi->nr; i++) {
struct plot_data *entry = pi->entry + i;
int pressure = get_plot_sensor_pressure(entry, sensor);
if (!pressure)
continue;
if (first < 0)
first = i;
last = i;
}
/* No sensor data at all? */
if (first == last)
return;
/*
* Split the range:
* - missing pressure data
* - gas change events to other cylinders
*
* Note that we only look at gas switches if this cylinder
* itself has a gas change event.
*/
cyl = sensor;
ev = NULL;
if (has_gaschange_event(dive, dc, sensor))
ev = get_next_event(dc->events, "gaschange");
b_ev = get_next_event(dc->events, "modechange");
for (int i = first; i <= last; i++) {
struct plot_data *entry = pi->entry + i;
int pressure = get_plot_sensor_pressure(entry, sensor);
int time = entry->sec;
while (ev && ev->time.seconds <= time) { // Find 1st gaschange event after
cyl = get_cylinder_index(dive, ev); // the current gas change.
if (cyl < 0)
cyl = sensor;
ev = get_next_event(ev->next, "gaschange");
}
while (b_ev && b_ev->time.seconds <= time) { // Keep existing divemode, then
dmode = b_ev->value; // find 1st divemode change event after the current
b_ev = get_next_event(b_ev->next, "modechange"); // divemode change.
}
if (current) { // calculate pressure-time, taking into account the dive mode for this specific segment.
entry->pressure_time = (int)(calc_pressure_time(dive, entry - 1, entry) * gasfactor[dmode] + 0.5);
current->pressure_time += entry->pressure_time;
current->t_end = entry->sec;
if (pressure)
current->end = pressure;
}
// We have a final pressure for 'current'
// If a gas switch has occurred, finish the
// current pressure track entry and continue
// until we get back to this cylinder.
if (cyl != sensor) {
current = NULL;
set_plot_pressure_data(entry, SENSOR_PR, sensor, 0);
continue;
}
// If we have no pressure information, we will need to
// continue with or without a tracking entry. Mark any
// existing tracking entry as non-dense, and remember
// to fill in interpolated data.
if (current && !pressure) {
missing_pr = 1;
dense = 0;
continue;
}
// If we already have a pressure tracking entry, and
// it has not had any missing samples, just continue
// using it - there's nothing to interpolate yet.
if (current && dense)
continue;
// We need to start a new tracking entry, either
// because the previous was interrupted by a gas
// switch event, or because the previous one has
// missing entries that need to be interpolated.
// Or maybe we didn't have a previous one at all,
// and this is the first pressure entry.
current = pr_track_alloc(pressure, entry->sec);
track = list_add(track, current);
dense = 1;
}
if (missing_pr) {
fill_missing_tank_pressures(dive, pi, track, sensor);
}
#ifdef PRINT_PRESSURES_DEBUG
debug_print_pressures(pi);
#endif
list_free(track);
}