[PATCH] Remove the tissue_tolerated_ambient_pressure[] array

[Linus Torvalds]

From: Linus Torvalds <torvalds at linux-foundation.org>
Date: Fri, 8 Feb 2013 21:42:34 +1100
Subject: [PATCH] Remove the tissue_tolerated_ambient_pressure[] array

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 at lmu.de>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
---

Ok, this is just the patch I sent earlier, except it now has a commit 
message and the addition of the acked-by from Robert, since he verified my 
thinking.

 deco.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/deco.c b/deco.c
index 023a20f72e20..4bddad576aea 100644
--- a/deco.c
+++ b/deco.c
@@ -79,7 +79,6 @@ const double buehlmann_He_factor_expositon_one_second[] = {
 
 double tissue_n2_sat[16];
 double tissue_he_sat[16];
-double tissue_tolerated_ambient_pressure[16];
 int ci_pointing_to_guiding_tissue;
 double gf_low_pressure_this_dive;
 #define TISSUE_ARRAY_SZ sizeof(tissue_n2_sat)
@@ -96,11 +95,13 @@ static double tissue_tolerance_calc(const struct dive *dive)
 
 	for (ci = 0; ci < 16; ci++)
 	{
+		double tolerated;
+
 		tissue_inertgas_saturation = tissue_n2_sat[ci] + tissue_he_sat[ci];
 		buehlmann_inertgas_a = ((buehlmann_N2_a[ci] * tissue_n2_sat[ci]) + (buehlmann_He_a[ci] * tissue_he_sat[ci])) / tissue_inertgas_saturation;
 		buehlmann_inertgas_b = ((buehlmann_N2_b[ci] * tissue_n2_sat[ci]) + (buehlmann_He_b[ci] * tissue_he_sat[ci])) / tissue_inertgas_saturation;
 
-		/* tissue_tolerated_ambient_pressure[ci] = (tissue_inertgas_saturation - buehlmann_inertgas_a) * buehlmann_inertgas_b; */
+		/* tolerated = (tissue_inertgas_saturation - buehlmann_inertgas_a) * buehlmann_inertgas_b; */
 
 #if !GF_LOW_AT_MAXDEPTH
 		lowest_ceiling = (buehlmann_inertgas_b * tissue_inertgas_saturation - gf_low * buehlmann_inertgas_a * buehlmann_inertgas_b) /
@@ -109,17 +110,17 @@ static double tissue_tolerance_calc(const struct dive *dive)
 			gf_low_pressure_this_dive = lowest_ceiling;
 #endif
 
-		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 +
-								buehlmann_inertgas_b * (gf_low_pressure_this_dive - surface) * tissue_inertgas_saturation) /
-							(-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) +
-								buehlmann_inertgas_b * (gf_low_pressure_this_dive - surface));
+		tolerated = (-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 +
+				buehlmann_inertgas_b * (gf_low_pressure_this_dive - surface) * tissue_inertgas_saturation) /
+			    (-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) +
+				buehlmann_inertgas_b * (gf_low_pressure_this_dive - surface));
 
-		if (tissue_tolerated_ambient_pressure[ci] > ret_tolerance_limit_ambient_pressure)
+		if (tolerated > ret_tolerance_limit_ambient_pressure)
 		{
 			ci_pointing_to_guiding_tissue = ci;
-			ret_tolerance_limit_ambient_pressure = tissue_tolerated_ambient_pressure[ci];
+			ret_tolerance_limit_ambient_pressure = tolerated;
 		}
 	}
 	return ret_tolerance_limit_ambient_pressure;
@@ -203,7 +204,6 @@ void clear_deco(double surface_pressure)
 	for (ci = 0; ci < 16; ci++) {
 		tissue_n2_sat[ci] = (surface_pressure - WV_PRESSURE) * N2_IN_AIR / 1000;
 		tissue_he_sat[ci] = 0.0;
-		tissue_tolerated_ambient_pressure[ci] = 0.0;
 	}
 	gf_low_pressure_this_dive = surface_pressure + buehlmann_config.gf_low_position_min;
 }
@@ -213,15 +213,13 @@ void cache_deco_state(double tissue_tolerance, char **cached_datap)
 	char *data = *cached_datap;
 
 	if (!data) {
-		data = malloc(3 * TISSUE_ARRAY_SZ + 2 * sizeof(double) + sizeof(int));
+		data = malloc(2 * TISSUE_ARRAY_SZ + 2 * sizeof(double) + sizeof(int));
 		*cached_datap = data;
 	}
 	memcpy(data, tissue_n2_sat, TISSUE_ARRAY_SZ);
 	data += TISSUE_ARRAY_SZ;
 	memcpy(data, tissue_he_sat, TISSUE_ARRAY_SZ);
 	data += TISSUE_ARRAY_SZ;
-	memcpy(data, tissue_tolerated_ambient_pressure, TISSUE_ARRAY_SZ);
-	data += TISSUE_ARRAY_SZ;
 	memcpy(data, &gf_low_pressure_this_dive, sizeof(double));
 	data += sizeof(double);
 	memcpy(data, &tissue_tolerance, sizeof(double));
@@ -237,8 +235,6 @@ double restore_deco_state(char *data)
 	data += TISSUE_ARRAY_SZ;
 	memcpy(tissue_he_sat, data, TISSUE_ARRAY_SZ);
 	data += TISSUE_ARRAY_SZ;
-	memcpy(tissue_tolerated_ambient_pressure, data, TISSUE_ARRAY_SZ);
-	data += TISSUE_ARRAY_SZ;
 	memcpy(&gf_low_pressure_this_dive, data, sizeof(double));
 	data += sizeof(double);
 	memcpy(&tissue_tolerance, data, sizeof(double));
-- 
1.8.1.3.535.ga923c31