[PATCH 2/2] Discontinuity and stall on tank pressure interpolated lines
Rodrigo Severo
rodrigo at fabricadeideias.com
Tue Dec 31 14:32:16 UTC 2013
Interpolated lines for tank pressures were presenting discontinuities (sudden drops) and stalls (horizontal lines) with certain dive profiles.
The main reason seems to be that the discrete interpolation of tank pressure was adding small pressure increments that could be rounded down or up repeatedly generating cumulative rounding errors that would mean either a delay on pressure drop that would be drawn as a sudden drop or as a premature pressure drop that would result in a flat line.
This patch changes the way the discrete interpolation is done, so that we don't have cumulative rounding errors distorting tank pressure lines.
To calculate accumulated pressure_time values the get_pr_interpolate_data function was created. The fact that get_pr_interpolate_data transverses the beginning of the plot_info entry list for each entry that needs interpolated tank pressure isn't optimal at all. There might be a way to properly track the data necessary to interpolate tank pressures from inside the main pi->entry loop in fill_missing_tank_pressures. Unfortunately I didn't manage to do it inside fill_missing_tank_pressures so we have get_pr_interpolate_data.
The SURFACE_THRESHOLD test from pressure_time function was also removed as no matter how shallow the diver is, if he is using the cylinder to breathe the cylinders tank pressure should be affected.
Signed-off-by: Rodrigo Severo <rodrigo at fabricadeideias.com>
---
profile.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----------
profile.h | 1 +
2 files changed, 82 insertions(+), 17 deletions(-)
diff --git a/profile.c b/profile.c
index ea387bf..6178a31 100644
--- a/profile.c
+++ b/profile.c
@@ -417,6 +417,22 @@ static void dump_pr_track(pr_track_t **track_pr)
}
#endif
+typedef struct pr_interpolate_struct pr_interpolate_t;
+struct pr_interpolate_struct {
+ int start;
+ int end;
+ int pressure_time;
+ int acc_pressure_time;
+};
+
+#ifdef DEBUG_PR_INTERPOLATE
+static void dump_pr_interpolate(pr_interpolate_t interpolate_pr)
+{
+ printf("INTERPOLATE: start %d - end %d - pt %d - acc_pt %d\n",
+ interpolate_pr.start, interpolate_pr.end, interpolate_pr.pressure_time, interpolate_pr.acc_pressure_time);
+}
+#endif
+
/*
* This looks at the pressures for one cylinder, and
* calculates any missing beginning/end pressures for
@@ -473,7 +489,7 @@ static void fill_missing_segment_pressures(pr_track_t *list)
if (pt_sum)
pressure -= (start-end)*(double)pt/pt_sum;
list->end = pressure;
- if (list == tmp)
+ if (list == tmp)
break;
list = list->next;
list->start = pressure;
@@ -500,12 +516,57 @@ static inline int pressure_time(struct dive *dive, struct divecomputer *dc, stru
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;
}
+static struct pr_interpolate_struct get_pr_interpolate_data(pr_track_t *segment, struct plot_info *pi, int cur)
+{
+ struct pr_interpolate_struct interpolate;
+ int i;
+ struct plot_data *entry, *cur_entry;
+
+ interpolate.start = segment->start;
+ interpolate.end = segment->end;
+ interpolate.acc_pressure_time = 0;
+ interpolate.pressure_time = 0;
+ cur_entry = pi->entry + cur;
+
+ for (i = 0; i < pi->nr; i++) {
+ entry = pi->entry + i;
+ if (entry->sec < segment->t_start)
+ continue;
+ if (entry->sec >= segment->t_end) {
+ interpolate.pressure_time += entry->pressure_time;
+ break;
+ }
+ if (entry->sec == segment->t_start) {
+ interpolate.acc_pressure_time = 0;
+ interpolate.pressure_time = 0;
+ if (SENSOR_PRESSURE(entry))
+ interpolate.start = SENSOR_PRESSURE(entry);
+ } else if (i < cur) {
+ if (SENSOR_PRESSURE(entry)) {
+ interpolate.start = SENSOR_PRESSURE(entry);
+ interpolate.acc_pressure_time = 0;
+ interpolate.pressure_time = 0;
+ } else {
+ interpolate.acc_pressure_time += entry->pressure_time;
+ interpolate.pressure_time += entry->pressure_time;
+ }
+ } else if (i == cur) {
+ interpolate.acc_pressure_time += entry->pressure_time;
+ interpolate.pressure_time += entry->pressure_time;
+ } else {
+ interpolate.pressure_time += entry->pressure_time;
+ if (SENSOR_PRESSURE(entry)) {
+ interpolate.end = SENSOR_PRESSURE(entry);
+ break;
+ }
+ }
+ }
+ return interpolate;
+}
+
static void fill_missing_tank_pressures(struct dive *dive, struct plot_info *pi, pr_track_t **track_pr)
{
int cyl, i;
@@ -526,19 +587,19 @@ static void fill_missing_tank_pressures(struct dive *dive, struct plot_info *pi,
/* The first two are "fillers", but in case we don't have a sample
* at time 0 we need to process the second of them here */
for (i = 1; i < pi->nr; i++) {
- double magic, cur_pt;
+ double magic;
pr_track_t *segment;
- int pressure;
+ pr_interpolate_t interpolate;
entry = pi->entry + i;
cyl = entry->cylinderindex;
-
+
if (SENSOR_PRESSURE(entry)) {
cur_pr[cyl] = SENSOR_PRESSURE(entry);
continue;
}
-
- /* Find the right pressure segment for this entry.. */
+
+ /* Find the right pressure segment for this entry.. */
segment = track_pr[cyl];
while (segment && segment->t_end < entry->sec)
segment = segment->next;
@@ -548,15 +609,17 @@ static void fill_missing_tank_pressures(struct dive *dive, struct plot_info *pi,
SENSOR_PRESSURE(entry) = cur_pr[cyl];
continue;
}
-
+
+ interpolate = get_pr_interpolate_data(segment, pi, i);
+#ifdef DEBUG_PR_INTERPOLATE
+ dump_pr_interpolate(interpolate);
+#endif
/* Overall pressure change over total pressure-time for this segment*/
- magic = (segment->end - segment->start) / (double) segment->pressure_time;
+ magic = (interpolate.end - interpolate.start) / (double) interpolate.pressure_time;
/* Use that overall pressure change to update the current pressure */
- cur_pt = pressure_time(dive, &dive->dc, entry-1, entry);
- pressure = cur_pr[cyl] + cur_pt * magic + 0.5;
- INTERPOLATED_PRESSURE(entry) = pressure;
- cur_pr[cyl] = pressure;
+ cur_pr[cyl] = interpolate.start + magic * interpolate.acc_pressure_time + 0.5;
+ INTERPOLATED_PRESSURE(entry) = cur_pr[cyl];
}
}
@@ -906,7 +969,8 @@ static void populate_pressure_information(struct dive *dive, struct divecomputer
/* discrete integration of pressure over time to get the SAC rate equivalent */
if (current) {
- current->pressure_time += pressure_time(dive, dc, entry-1, entry);
+ entry->pressure_time = pressure_time(dive, dc, entry-1, entry);
+ current->pressure_time += entry->pressure_time;
current->t_end = entry->sec;
}
@@ -1137,7 +1201,7 @@ struct plot_info *create_plot_info(struct dive *dive, struct divecomputer *dc, s
if (last_pi_entry)
free((void *)last_pi_entry);
last_pi_entry = populate_plot_entries(dive, dc, pi);
-
+
/* Populate the gas index from the gas change events */
check_gas_change_events(dive, dc, pi);
diff --git a/profile.h b/profile.h
index c64ecfb..9f759d8 100644
--- a/profile.h
+++ b/profile.h
@@ -41,6 +41,7 @@ struct plot_data {
int tts_calc;
int stoptime_calc;
int stopdepth_calc;
+ int pressure_time;
};
void calculate_max_limits(struct dive *dive, struct divecomputer *dc, struct graphics_context *gc);
--
1.8.3.2
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