[PATCH 1/3] Simplify/clarify the get_surface_pressure_in_mbar() function
Linus Torvalds
torvalds at linux-foundation.org
Fri Feb 8 16:48:03 PST 2013
From: Linus Torvalds <torvalds at linux-foundation.org>
Date: Sat, 9 Feb 2013 10:23:15 +1100
Subject: [PATCH 1/3] Simplify/clarify the get_surface_pressure_in_mbar() function
Instead of maintaining a rolling average and re-calculating it at each
stage, just calculate the surface_pressure average the natural way: as
the sum divided by the number of entries.
This results in a single rounding, rather than doing rounding multiple
times and possibly rounding wrong as a result.
Not that we care all that deeply about the LSB of the mbar value, but
the code is simpler and more obvious this way too.
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
---
The next few patches will change this more, so the lines get moved around
etc, but the change to the basic algorithm is conceptually a different
thing..
dive.c | 25 +++++++++++++++----------
statistics.c | 7 ++++---
2 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/dive.c b/dive.c
index 7083e857c03b..cbee208ec7e6 100644
--- a/dive.c
+++ b/dive.c
@@ -232,18 +232,23 @@ int get_duration_in_sec(struct dive *dive)
int get_surface_pressure_in_mbar(const struct dive *dive, gboolean non_null)
{
- int count = 0, pressure = 0;
+ unsigned int count = 0, sum = 0;
const struct divecomputer *dc = &dive->dc;
+
do {
- if (dc->surface_pressure.mbar) {
- pressure = (double)(count * pressure + dc->surface_pressure.mbar) / (count + 1) + 0.5;
- count++;
- }
- dc = dc->next;
- } while (dc);
- if (!pressure && non_null)
- pressure = SURFACE_PRESSURE;
- return pressure;
+ if (!dc->surface_pressure.mbar)
+ continue;
+ sum += dc->surface_pressure.mbar;
+ count++;
+ } while ((dc = dc->next) != NULL);
+
+ /* Did we have any dive computers with surface pressure information */
+ if (count)
+ return (sum + count/2) / count;
+
+ if (non_null)
+ return SURFACE_PRESSURE;
+ return 0;
}
static void update_temperature(temperature_t *temperature, int new)
diff --git a/statistics.c b/statistics.c
index 82070a937479..d7abbc592483 100644
--- a/statistics.c
+++ b/statistics.c
@@ -539,7 +539,7 @@ static void show_single_dive_stats(struct dive *dive)
double value;
int decimals;
const char *unit;
- int idx, offset, gas_used;
+ int idx, offset, gas_used, mbar;
struct dive *prev_dive;
struct tm tm;
@@ -579,8 +579,9 @@ static void show_single_dive_stats(struct dive *dive)
} else {
set_label(single_w.air_temp, "");
}
- if (get_surface_pressure_in_mbar(dive, FALSE)) {
- set_label(single_w.air_press, "%d mbar", dive->dc.surface_pressure.mbar);
+ mbar = get_surface_pressure_in_mbar(dive, FALSE);
+ if (mbar) {
+ set_label(single_w.air_press, "%d mbar", mbar);
} else {
set_label(single_w.air_press, _("unknown"));
}
--
1.8.1.3.535.ga923c31
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