>
> Here are my result, on a Duron 1.3Ghz:
>
> ....
> ....
>
> The difference of speed between the first and the second test
> (with or without the null checks) is indeed really small (2.5%).
> But the diffence between the second and the third test is really
> more important (13.2%). So I will move the procedures of Jose
> to evas, with the null checks, and use it in Etk.
>
> Regards ;)
> Simon TRENY <MoOm>
>
The greater gains in the 'hsv_to_rgb' function are also
due to the elimination of some statements and variables there.
The 'rgb_to_hsv' func doesn't gain much from simply
removing the null checks since it's already being killed by
several such conditional checks...
Let's see if we can do better with this function :)
Here's the current version:
void
rgb_to_hsv(int r, int g, int b, float *h, float *s, float *v)
{
float min, max, del;
min = MIN(r,g); min = MIN(min,b);
max = MAX(r,g); max = MAX(max,b);
del = max - min;
*v = (max / 255);
if ((max == 0) || (del == 0))
{
*s = 0; *h = 0;
return;
}
*s = (del / max);
if (r == max)
*h = ((g - b) / del);
else if (g == max)
*h = 2 + ((b - r) / del);
else if (b == max)
*h = 4 + ((r - g) / del);
*h *= 60;
if (*h < 0) *h += 360;
}
Those MIN,MAX's have to go... But, how?
Let's note that if a and b are non-negative integers,
then the following relations hold:
max(a,b) = a + max(0,b - a)
min(a,b) = b - max(0,b - a)
So, if we can find a fast way to compute max(0,x)
for x an integer in some range, than we might get somewhere.
Fortunately, if the a,b are integers in the range
[0,255], so that x = b - a is in the range [-255,255], then
we can compute max(0,x) as ((x & (~(x >> 8))) & 0xff).
Let's also note that in the last part of the function,
we always multiply *h times 60, so lets put that into the
statements that give *h its initial values, and might as well
put the 'if (*h<0)..' check in those as well...
If we do these things, we can rewrite the function as:
void
rgb_to_hsv(int r, int g, int b, float *h, float *s, float *v)
{
int max, min, d = r - g;
// set min to MIN(g,r)
d = ((d & (~(d >> 8))) & 0xff);
min = r - d;
// set max to MAX(g,r)
max = g + d;
// set min to MIN(b,min)
d = min - b;
min -= ((d & (~(d >> 8))) & 0xff);
// set max to MAX(max,b)
d = b - max;
max += ((d & (~(d >> 8))) & 0xff);
d = max - min;
*v = (max / 255.0);
if (!(max & d))
{
*s = 0; *h = 0;
return;
}
*s = (d / (float)max);
if (r == max)
{
*h = 60 * ((g - b) / (float)d);
if (*h < 0) *h += 360;
return;
}
if (g == max)
{
*h = 120 + (60 * ((b - r) / (float)d));
if (*h < 0) *h += 360;
return;
}
*h = 240 + (60 * ((r - g) / (float)d));
if (*h < 0) *h += 360;
}
These very simple changes will now give us roughly 20+%
gains in this function as well.
jose.
-------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid0709&bid&3057&dat1642
_______________________________________________
enlightenment-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
