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Faster ff_sqrt() 

Originally committed as revision 11586 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2008-01-21 13:33:18 +00:00
parent b21cd0bcb5
commit c448a09624
2 changed files with 27 additions and 19 deletions
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32
libavutil/internal.h
View File

@ -178,24 +178,28 @@ extern const uint32_t ff_inverse[256];
# define FASTDIV(a,b) ((a)/(b))
#endif
extern const uint8_t ff_sqrt_tab[128];
extern const uint8_t ff_sqrt_tab[256];
static inline int ff_sqrt(int a)
static inline int av_log2_16bit(unsigned int v);
static inline unsigned int ff_sqrt(unsigned int a)
{
int ret=0;
int s, b;
unsigned int b;
if(a<128) return ff_sqrt_tab[a];
for(s=30; s>=0; s-=2){
ret+=ret;
b= (1+2*ret)<<s;
if(b<=a){
a-=b;
ret++;
}
if(a<255) return (ff_sqrt_tab[a+1]-1)>>4;
else if(a<(1<<12)) b= ff_sqrt_tab[a>>4 ]>>2;
#ifndef CONFIG_SMALL
else if(a<(1<<14)) b= ff_sqrt_tab[a>>6 ]>>1;
else if(a<(1<<16)) b= ff_sqrt_tab[a>>8 ] ;
#endif
else{
int s= av_log2_16bit(a>>16)>>1;
unsigned int c= a>>(s+2);
b= ff_sqrt_tab[c>>(s+8)];
b= FASTDIV(c,b) + (b<<s);
}
return ret;
return b - (a<b*b);
}
#if defined(ARCH_X86)

14
libavutil/mathematics.c
View File

@ -26,11 +26,15 @@
#include "common.h"
#include "mathematics.h"
const uint8_t ff_sqrt_tab[128]={
0, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5,
5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
9, 9, 9, 9,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,11,11,11,11,11,11,11
const uint8_t ff_sqrt_tab[256]={
0, 16, 23, 28, 32, 36, 40, 43, 46, 48, 51, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 77, 79, 80, 82, 84, 85, 87, 88, 90,
91, 92, 94, 95, 96, 98, 99,100,102,103,104,105,107,108,109,110,111,112,114,115,116,117,118,119,120,121,122,123,124,125,126,127,
128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,144,145,146,147,148,149,150,151,151,152,153,154,155,156,156,
157,158,159,160,160,161,162,163,164,164,165,166,167,168,168,169,170,171,171,172,173,174,174,175,176,176,177,178,179,179,180,181,
182,182,183,184,184,185,186,186,187,188,188,189,190,190,191,192,192,193,194,194,195,196,196,197,198,198,199,200,200,201,202,202,
203,204,204,205,205,206,207,207,208,208,209,210,210,211,212,212,213,213,214,215,215,216,216,217,218,218,219,219,220,220,221,222,
222,223,223,224,224,225,226,226,227,227,228,228,229,230,230,231,231,232,232,233,233,234,235,235,236,236,237,237,238,238,239,239,
240,240,241,242,242,243,243,244,244,245,245,246,246,247,247,248,248,249,249,250,250,251,251,252,252,253,253,254,254,255,255,255
};
const uint8_t ff_log2_tab[256]={