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tiny polish to hist_find

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slightly faster again
This commit is contained in:
John Cupitt 2016-02-28 12:08:06 +00:00
parent e46e2b7b28
commit e582f13d13
2 changed files with 46 additions and 28 deletions
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1
ChangeLog
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@ -12,6 +12,7 @@
- sharpen defaults now suitable for screen output
- better handling of deprecated args in python
- much better handling of arrayimage command-line args
- faster hist_find (Lovell Fuller)
27/1/16 started 8.2.3
- fix a crash with SPARC byte-order labq vips images

73
libvips/arithmetic/hist_find.c
View File

@ -24,6 +24,8 @@
* - cast @in to u8/u16.
* 12/8/13
* - redo as a class
* 28/2/16 lovell
* - unroll common cases
*/
/*
@ -233,50 +235,62 @@ vips_hist_find_uchar_scan( VipsStatistic *statistic,
void *seq, int x, int y, void *in, int n )
{
Histogram *hist = (Histogram *) seq;
unsigned int *bins = hist->bins[0];
int nb = statistic->ready->Bands;
VipsPel *p = (VipsPel *) in;
int i, j, z;
int j;
/* The inner loop cannot be auto-vectorized by the compiler.
* Images with 1-4 bands are manually unrolled to improve
* performance for the most common cases by a factor of two.
* Unroll for common cases.
*/
switch (nb) {
switch( nb ) {
case 1:
for( i = 0, j = 0; j < n; j++, i++ )
hist->bins[0][p[i]] += 1;
for( j = 0; j < n; j++ )
bins[p[j]] += 1;
break;
case 2:
for( i = 0, j = 0; j < n; j++ ) {
hist->bins[0][p[i]] += 1;
hist->bins[1][p[i + 1]] += 1;
i += 2;
for( j = 0; j < n; j++ ) {
hist->bins[0][p[0]] += 1;
hist->bins[1][p[1]] += 1;
p += 2;
}
break;
case 3:
for( i = 0, j = 0; j < n; j++ ) {
hist->bins[0][p[i]] += 1;
hist->bins[1][p[i + 1]] += 1;
hist->bins[2][p[i + 2]] += 1;
i += 3;
for( j = 0; j < n; j++ ) {
hist->bins[0][p[0]] += 1;
hist->bins[1][p[1]] += 1;
hist->bins[2][p[2]] += 1;
p += 3;
}
break;
case 4:
for( i = 0, j = 0; j < n; j++ ) {
hist->bins[0][p[i]] += 1;
hist->bins[1][p[i + 1]] += 1;
hist->bins[2][p[i + 2]] += 1;
hist->bins[3][p[i + 3]] += 1;
i += 4;
for( j = 0; j < n; j++ ) {
hist->bins[0][p[0]] += 1;
hist->bins[1][p[1]] += 1;
hist->bins[2][p[2]] += 1;
hist->bins[3][p[3]] += 1;
p += 4;
}
break;
default:
/* Loop when >4 bands
*/
for( i = 0, j = 0; j < n; j++ )
for( z = 0; z < nb; z++, i++ )
hist->bins[z][p[i]] += 1;
for( j = 0; j < n; j++ ) {
int z;
for( z = 0; z < nb; z++ )
hist->bins[z][p[z]] += 1;
p += nb;
}
}
/* Note the maximum.
@ -321,11 +335,11 @@ vips_hist_find_ushort_scan( VipsStatistic *statistic,
int nb = statistic->ready->Bands;
unsigned short *p = (unsigned short *) in;
int i, j, z;
int j, z;
for( i = 0, j = 0; j < n; j++ )
for( z = 0; z < nb; z++, i++ ) {
int v = p[i];
for( j = 0; j < n; j++ ) {
for( z = 0; z < nb; z++ ) {
int v = p[z];
/* Adjust maximum.
*/
@ -335,6 +349,9 @@ vips_hist_find_ushort_scan( VipsStatistic *statistic,
hist->bins[z][v] += 1;
}
p += nb;
}
/* Note the maximum.
*/
hist->mx = mx;