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optimisation: another bunch of simplifications to the "simple case" of the

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alg_quant() search.
This commit is contained in:
Jean-Marc Valin 2008-04-15 17:31:23 +10:00
parent 6ea8baed2d
commit ed317c94c3
2 changed files with 38 additions and 29 deletions
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1
libcelt/cwrs.c
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@ -42,6 +42,7 @@
#include "config.h"
#endif
#include "os_support.h"
#include <stdlib.h>
#include <string.h>
#include "cwrs.h"

66
libcelt/vq.c
View file

@ -137,61 +137,67 @@ void alg_quant(celt_norm_t *X, celt_mask_t *W, int N, int K, const celt_norm_t *
while (pulsesLeft > 0)
{
int pulsesAtOnce=1;
int sign;
celt_word32_t Rxy, Ryy, Ryp;
celt_word32_t g;
celt_word32_t best_num;
celt_word16_t best_den;
int best_id;
celt_word16_t magnitude;
#ifdef FIXED_POINT
int rshift;
#endif
/* Decide on how many pulses to find at once */
pulsesAtOnce = (pulsesLeft*N_1)>>9; /* pulsesLeft/N */
if (pulsesAtOnce<1)
pulsesAtOnce = 1;
#ifdef FIXED_POINT
rshift = yshift+1+celt_ilog2(K-pulsesLeft+pulsesAtOnce);
#endif
magnitude = SHL16(pulsesAtOnce, yshift);
/* This should ensure that anything we can process will have a better score */
best_num = -SHR32(VERY_LARGE32,4);
best_den = 0;
best_id = 0;
/* The squared magnitude term gets added anyway, so we might as well
add it outside the loop */
yy = ADD32(yy, MULT16_16(magnitude,magnitude));
/* Choose between fast and accurate strategy depending on where we are in the search */
if (pulsesLeft>1)
{
/* OPT: This loop is very CPU-intensive */
/* This should ensure that anything we can process will have a better score */
celt_word32_t best_num = -VERY_LARGE16;
celt_word16_t best_den = 0;
j=0;
do {
celt_word32_t num;
celt_word16_t den;
celt_word16_t Rxy, Ryy;
/* Select sign based on X[j] alone */
sign = signx[j];
s = SHL16(sign*pulsesAtOnce, yshift);
s = signx[j]*magnitude;
/* Temporary sums of the new pulse(s) */
Rxy = xy + MULT16_16(s,X[j]);
Ryy = yy + 2*MULT16_16(s,y[j]) + MULT16_16(s,s);
Rxy = SHR32(xy + MULT16_16(s,X[j]),rshift);
/* We're multiplying y[j] by two so we don't have to do it here */
Ryy = SHR32(yy + MULT16_16(s,y[j]),rshift);
/* Approximate score: we maximise Rxy/sqrt(Ryy) */
num = MULT16_16(ROUND16(Rxy,14),ABS16(ROUND16(Rxy,14)));
den = ROUND16(Ryy,14);
/* Approximate score: we maximise Rxy/sqrt(Ryy) (we're guaranteed that
Rxy is positive because the sign is pre-computed) */
Rxy = MULT16_16_Q15(Rxy,Rxy);
/* The idea is to check for num/den >= best_num/best_den, but that way
we can do it without any division */
/* OPT: Make sure to use a conditional move here */
if (MULT16_32_Q15(best_den, num) > MULT16_32_Q15(den, best_num))
/* OPT: Make sure to use conditional moves here */
if (MULT16_16(best_den, Rxy) > MULT16_16(Ryy, best_num))
{
best_den = den;
best_num = num;
best_den = Ryy;
best_num = Rxy;
best_id = j;
}
} while (++j<N); /* Promises we loop at least once */
} else {
celt_word32_t g;
celt_word32_t best_num = -VERY_LARGE32;
for (j=0;j<N;j++)
{
celt_word32_t Rxy, Ryy, Ryp;
celt_word32_t num;
/* Select sign based on X[j] alone */
sign = signx[j];
s = SHL16(sign*pulsesAtOnce, yshift);
s = signx[j]*magnitude;
/* Temporary sums of the new pulse(s) */
Rxy = xy + MULT16_16(s,X[j]);
Ryy = yy + 2*MULT16_16(s,y[j]) + MULT16_16(s,s);
Ryp = yp + MULT16_16(s, P[j]);
/* We're multiplying y[j] by two so we don't have to do it here */
Ryy = yy + MULT16_16(s,y[j]);
Ryp = yp + MULT16_16(s,P[j]);
/* Compute the gain such that ||p + g*y|| = 1 */
g = MULT16_32_Q15(
@ -218,11 +224,13 @@ void alg_quant(celt_norm_t *X, celt_mask_t *W, int N, int K, const celt_norm_t *
/* Updating the sums of the new pulse(s) */
xy = xy + MULT16_16(s,X[j]);
yy = yy + 2*MULT16_16(s,y[j]) + MULT16_16(s,s);
/* We're multiplying y[j] by two so we don't have to do it here */
yy = yy + MULT16_16(s,y[j]);
yp = yp + MULT16_16(s, P[j]);
/* Only now that we've made the final choice, update y/iy */
y[j] += s;
/* Multiplying y[j] by 2 so we don't have to do it everywhere else */
y[j] += 2*s;
iy[j] += is;
pulsesLeft -= pulsesAtOnce;
}