diff options
author | Explorer09 <explorer09@gmail.com> | 2016-01-21 14:06:11 +0800 |
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committer | Explorer09 <explorer09@gmail.com> | 2016-01-21 14:06:11 +0800 |
commit | 040613db3315aeb992208d30789807285316f3b9 (patch) | |
tree | 27e71f686be35e22c7770fef41af0de57c05773c /Meter.c | |
parent | d54ab24d9728e09965e7ed04fa3502a8420ba748 (diff) |
Change variable 'dot' to avoid division by reciprocal.
(Cherry-picked from d56bcd8e0d8d6a177fc2e40db32fc73ea4588684, the
experimental graph coloring branch)
The variable 'dot' in GraphMeterMode_draw now means "maximum number of
dots per value (column) in graph". The old meaning was "amount of value
that is to be represented by a dot" and was always a fraction. Due to
a limitation in floating point computing, if GRAPH_HEIGHT were not a
power of 2, then rounding errors will occur on numbers like (1.0/3).
(Currently GRAPH_HEIGHT is 4 and so no precision loss.) 'dot' was used
as a divisor, and it's "division by a reciprocal". We change that to
simple multiplication.
Diffstat (limited to 'Meter.c')
-rw-r--r-- | Meter.c | 6 |
1 files changed, 3 insertions, 3 deletions
@@ -408,9 +408,9 @@ static void GraphMeterMode_draw(Meter* this, int x, int y, int w) { } for (int i = nValues - (w*2) + 2, k = 0; i < nValues; i+=2, k++) { - const double dot = (1.0 / (GraphMeterMode_pixPerRow * GRAPH_HEIGHT)); - int v1 = CLAMP(data->values[i] / dot, 1, GraphMeterMode_pixPerRow * GRAPH_HEIGHT); - int v2 = CLAMP(data->values[i+1] / dot, 1, GraphMeterMode_pixPerRow * GRAPH_HEIGHT); + int pix = GraphMeterMode_pixPerRow * GRAPH_HEIGHT; + int v1 = CLAMP(data->values[i] * pix, 1, pix); + int v2 = CLAMP(data->values[i+1] * pix, 1, pix); int colorIdx = GRAPH_1; for (int line = 0; line < GRAPH_HEIGHT; line++) { |