CCR patch: Reorganise the oxygen partial pressure calculations

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>

1 files changed, 122 insertions, 33 deletions

diff --git a/profile.c b/profile.c
index 10aa9c898..4f019ba33 100644
--- a/profile.c
+++ b/profile.c
@@ -16,10 +16,14 @@
 #include "libdivecomputer/version.h"
 #include "membuffer.h"
 
+
+//#define DEBUG_GAS 1
+
 int selected_dive = -1; /* careful: 0 is a valid value */
 unsigned int dc_number = 0;
 
 static struct plot_data *last_pi_entry_new = NULL;
+double calculate_ccr_po2(struct plot_data *entry, struct divecomputer *dc);
 
 void fill_missing_segment_pressures(pr_track_t *);
 struct pr_interpolate_struct get_pr_interpolate_data(pr_track_t *, struct plot_info *, int);
@@ -507,8 +511,8 @@ struct plot_data *populate_plot_entries(struct dive *dive, struct divecomputer *
 		struct plot_data *entry = plot_data + idx;
 		struct sample *sample = dc->sample + i;
 		int time = sample->time.seconds;
-		int depth = sample->depth.mm;
 		int offset, delta;
+		int depth = sample->depth.mm;
 
 		/* Add intermediate plot entries if required */
 		delta = time - lasttime;
@@ -552,12 +556,14 @@ struct plot_data *populate_plot_entries(struct dive *dive, struct divecomputer *
 		pi->has_ndl |= sample->ndl.seconds;
 		entry->in_deco = sample->in_deco;
 		entry->cns = sample->cns;
-		entry->pressures.o2 = sample->po2.mbar / 1000.0;
-		entry->pressures.setpoint = sample->o2setpoint.mbar / 1000.0;   // for rebreathers
-		entry->pressures.sensor[0] = sample->o2sensor[0].mbar / 1000.0; // for up to three rebreather O2 sensors
-		entry->pressures.sensor[1] = sample->o2sensor[1].mbar / 1000.0;
-		entry->pressures.sensor[2] = sample->o2sensor[2].mbar / 1000.0;
-
+		if (dc->dctype == CCR) {
+			entry->o2setpoint = sample->o2setpoint.mbar / 1000.0;   // for rebreathers
+			entry->o2sensor[0] = sample->o2sensor[0].mbar / 1000.0; // for up to three rebreather O2 sensors
+			entry->o2sensor[1] = sample->o2sensor[1].mbar / 1000.0;
+			entry->o2sensor[2] = sample->o2sensor[2].mbar / 1000.0;
+		} else {
+			entry->pressures.o2 = sample->po2.mbar / 1000.0;
+		}
 		/* FIXME! sensor index -> cylinder index translation! */
 		entry->cylinderindex = sample->sensor;
 		SENSOR_PRESSURE(entry) = sample->cylinderpressure.mbar;
@@ -754,7 +760,6 @@ static void calculate_ndl_tts(double tissue_tolerance, struct plot_data *entry,
 }
 
 /* Let's try to do some deco calculations.
- * Needs to be run before calculate_gas_information so we know that if we have a po2, where in ccr-mode.
  */
 void calculate_deco_information(struct dive *dive, struct divecomputer *dc, struct plot_info *pi, bool print_mode)
 {
@@ -820,6 +825,85 @@ void calculate_deco_information(struct dive *dive, struct divecomputer *dc, stru
 #endif
 }
 
+
+/* Function calculate_ccr_po2: This function takes information from one plot_data structure (i.e. one point on
+ * the dive profile), containing the oxygen sensor values of a CCR system and, for that plot_data structure,
+ * calculates the po2 value from the sensor data. Several rules are applied, depending on how many o2 sensors
+ * there are and the differences among the readings from these sensors.
+ */
+double calculate_ccr_po2(struct plot_data *entry, struct divecomputer *dc) {
+	double sensor_j, sump, midp, minp, maxp;
+	double diff_limit = 100; // The limit beyond which O2 sensor differences are considered significant (default = 100 mbar)
+	int num_of_diffs;	 // The number of unacceptable differences among the ogygen sensor partial pressure measurements
+	int i, j, np;
+	bool maxdif = false, mindif = false;
+	struct gas_pressures *pressures = &(entry->pressures);
+
+	// Estimate the most reliable PO2, given the different oxygen partial pressure values from the O2 sensors
+	switch (dc->no_o2sensors) {
+		case 2: { // For 2 sensors: take the mean value of the two partial pressure sensors.
+			for (np = 0, sump = 0, j = 0; j < 2; j++) { // This calculation allows that for some samples
+				if (entry->o2sensor[j]) {	// (especially at start of dive) with an inactive sensor,the
+					np++; 			// sensor(s) with zero values are not used.
+					sump = sump + entry->o2sensor[j];
+				}
+			}
+			if (np > 0)			// if there is at least one sensor value
+				return (sump / np);	// then calculate the mean, else
+			else
+				return 0; // if there are no valid sensor values, calculate po2 on the basis of depth.
+			break;
+		}
+		case 3: { /* For 3 sensors: diff_limit is the critical limit indicating unacceptable difference (default = 100 mbar).
+			   * a) If all three readings are within a range of diff_limit, then take the mean value. This
+			   *     includes the case where reading 1 is within diff_limit of reading 2; and reading 2 is
+			   *     within diff_limit of reading 3, but readings 1 and 3 differ by more than diff_limit.
+			   * b) If one sensor differs by more than diff-limit from the other two, then take the mean
+			   *     of the closer two sensors and disregard the 3rd sensor, considered as an outlier.
+			   * c) If all 3 sensors differ by more than diff_limit then take the mean of the 3 readings. */
+			for (minp = 9999999999, maxp = -1, sump = 0, j = 0; j < 3; j++) {
+				sensor_j = entry->o2sensor[j];
+				if (sensor_j < minp)
+					minp = sensor_j;
+				if (sensor_j > maxp)
+					maxp = sensor_j;
+				sump = sump + sensor_j; // Find min, max and mid of p-values
+			}
+			midp = sump - minp - maxp;
+			num_of_diffs = 0;
+			if ((maxp - midp) > diff_limit) {
+				num_of_diffs++;
+				maxdif = true;
+			}
+			if ((midp - minp) > diff_limit) {
+				num_of_diffs++;
+				mindif = true; // Find no of unacceptable differences
+			}
+			switch (num_of_diffs) {
+			case 0:
+				;
+			case 2: {
+				return (sump / 3); // 0 or 2 unacceptable differences: find mean of three values.
+				break;
+			}
+			case 1: {
+				if (maxdif) // 1 unacceptable difference: find mean of two closer values
+					return ((minp + midp) / 2);
+				 else if (mindif)
+					return ((maxp + midp) / 2);
+				break;
+			}
+			} //switch no_of_diffs
+		}
+		default: { // if # of sensors is 1 or unknown, simply take the value of the first sensor
+			if (entry->o2sensor[0])
+				return (entry->o2sensor[0]);
+			else
+				return 0; // if no sensor value found, then go to next section, esimating PO2 using depth.
+		}
+	} // switch
+}
+
 static void calculate_gas_information_new(struct dive *dive, struct plot_info *pi)
 {
 	int i;
@@ -834,7 +918,7 @@ static void calculate_gas_information_new(struct dive *dive, struct plot_info *p
 		fo2 = get_o2(&dive->cylinder[cylinderindex].gasmix);
 		fhe = get_he(&dive->cylinder[cylinderindex].gasmix);
 
-		fill_pressures(&entry->pressures, amb_pressure, &dive->cylinder[cylinderindex].gasmix, entry->pressures.o2, &(dive->dc));
+		fill_pressures(&entry->pressures, amb_pressure, &dive->cylinder[cylinderindex].gasmix, entry->pressures.o2);
 
 		/* Calculate MOD, EAD, END and EADD based on partial pressures calculated before
 		 * so there is no difference in calculating between OC and CC
@@ -860,7 +944,7 @@ static void calculate_gas_information_new(struct dive *dive, struct plot_info *p
 	}
 }
 
-void fill_o2_values(struct divecomputer *dc, struct plot_info *pi)
+void fill_o2_values(struct divecomputer *dc, struct plot_info *pi, struct dive *dive)
 /* For CCR:
  * In the samples from each dive computer, any duplicate values for the
  * oxygen sensors were removed (i.e. set to 0) in order to conserve
@@ -871,33 +955,38 @@ void fill_o2_values(struct divecomputer *dc, struct plot_info *pi)
  * that the oxygen sensor data are complete and ready for plotting.
  * The original sequence of oxygen values are recreated without attempting
  * any interpolations for values set to zero, recreating the raw data from
- * the CCR dive log. This function called by: create_plot_info_new()    */
+ * the CCR dive log. This function called by: create_plot_info_new() */
 {
 	int i, j;
-	double last_setpoint;
-	double last_sensor[3];
+	double last_setpoint, last_sensor[3], o2pressure, amb_pressure;
+	struct gas_pressures *pressures;
 
 	for (i = 0; i < pi->nr; i++) {
 		struct plot_data *entry = pi->entry + i;
-
+		pressures = &(entry->pressures);
 		// For 1st iteration, initialise the last_ values
-		if (i == 0) {
-			last_setpoint = pi->entry->pressures.setpoint;
-			for (j = 0; j < dc->no_o2sensors; j++)
-				last_sensor[j] = pi->entry->pressures.sensor[j];
-		} else {
-			// Now re-insert the missing oxygen pressure values
-			if (entry->pressures.setpoint)
-				last_setpoint = entry->pressures.setpoint;
-			else
-				entry->pressures.setpoint = last_setpoint;
-
-			for (j = 0; j < dc->no_o2sensors; j++)
-				if (entry->pressures.sensor[j])
-					last_sensor[j] = entry->pressures.sensor[j];
+		if (dc->dctype == CCR) {
+			if (i == 0) {
+				last_setpoint = pi->entry->o2setpoint;
+				for (j = 0; j < dc->no_o2sensors; j++)
+					last_sensor[j] = pi->entry->o2sensor[j];
+			} else {
+				// Now re-insert the missing oxygen pressure values
+				if (entry->o2setpoint)
+					last_setpoint = entry->o2setpoint;
 				else
-					entry->pressures.sensor[j] = last_sensor[j];
+					entry->o2setpoint = last_setpoint;
+				for (j = 0; j < dc->no_o2sensors; j++)
+					if (entry->o2sensor[j])
+						last_sensor[j] = entry->o2sensor[j];
+					else
+						entry->o2sensor[j] = last_sensor[j];
+			}
 		}
+		amb_pressure = depth_to_mbar(entry->depth, dive) / 1000.0;
+		o2pressure = calculate_ccr_po2(entry,dc);
+		if (o2pressure > amb_pressure) o2pressure = amb_pressure;
+		entry->pressures.o2 = o2pressure;
 	}
 }
 
@@ -918,7 +1007,7 @@ static void debug_print_profiledata(struct plot_info *pi)
 			entry = pi->entry + i;
 			fprintf(f1, "%d gas=%8d %8d ; dil=%8d %8d ; o2_sp= %f %f %f %f PO2= %f\n", i, SENSOR_PRESSURE(entry),
 				INTERPOLATED_PRESSURE(entry), DILUENT_PRESSURE(entry), INTERPOLATED_DILUENT_PRESSURE(entry),
-				entry->o2setpoint, entry->pressures->sensor[0], entry->pressures->sensor[1], entry->pressures->sensor[2], entry->pressures.o2);
+				entry->o2setpoint, entry->o2sensor[0], entry->o2sensor[1], entry->o2sensor[2], entry->pressures.o2);
 		}
 		fclose(f1);
 	}
@@ -956,11 +1045,11 @@ void create_plot_info_new(struct dive *dive, struct divecomputer *dc, struct plo
 	if (dc->dctype == CCR) {				 /* For CCR dives.. */
 		printf("CCR DIVE: %s (%d O2 sensors)\n", dc->model, dc->no_o2sensors);
 		populate_pressure_information(dive, dc, pi, DILUENT); /* .. calculate missing diluent gas pressure entries */
-		fill_o2_values(dc, pi);				      /* .. and insert the O2 sensor data having 0 values. */
 	}
+	fill_o2_values(dc, pi, dive);				      /* .. and insert the O2 sensor data having 0 values. */
 	calculate_sac(dive, pi); /* Calculate sac */
-	calculate_deco_information(dive, dc, pi, false);
-	calculate_gas_information_new(dive, pi); /* And finaly calculate gas partial pressures */
+	calculate_deco_information(dive, dc, pi, false); /* and ceiling information, using gradient factor values in Preferences) */
+	calculate_gas_information_new(dive, pi); /* Calculate gas partial pressures */
 
 #ifdef DEBUG_GAS
 	debug_print_profiledata(pi);