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HLLCOUNT 3x faster taking fast path for default params.

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antirez 2014-03-29 12:12:44 +01:00
parent 28dce36f76
commit 3ed947fb30
1 changed files with 46 additions and 10 deletions
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56
src/hyperloglog.c
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@ -290,16 +290,52 @@ uint64_t hllCount(uint8_t *registers) {
initialized = 1;
}
/* Compute SUM(2^-register[0..i]). */
for (j = 0; j < REDIS_HLL_REGISTERS; j++) {
unsigned long reg;
/* Compute SUM(2^-register[0..i]).
* Redis default is to use 16384 registers 6 bits each. The code works
* with other values by modifying the defines, but for our target value
* we take a faster path with unrolled loops. */
if (REDIS_HLL_REGISTERS == 16384 && REDIS_HLL_BITS == 6 && 1) {
uint8_t *r = registers;
unsigned long r0, r1, r2, r3, r4, r5, r6, r7, r8, r9,
r10, r11, r12, r13, r14, r15;
for (j = 0; j < 1024; j++) {
/* Handle 16 registers per iteration. */
r0 = r[0] & 63; if (r0 == 0) ez++;
r1 = (r[0] << 6 | r[1] >> 2) & 63; if (r1 == 0) ez++;
r2 = (r[1] << 4 | r[2] >> 4) & 63; if (r2 == 0) ez++;
r3 = ((r[2] << 2) | (r[3] >> 6)) & 63; if (r3 == 0) ez++;
r4 = (r[3] | r[4] >> 8) & 63; if (r4 == 0) ez++;
r5 = (r[3] << 6 | r[4] >> 2) & 63; if (r5 == 0) ez++;
r6 = (r[4] << 4 | r[5] >> 4) & 63; if (r6 == 0) ez++;
r7 = (r[5] << 2 | r[6] >> 6) & 63; if (r7 == 0) ez++;
r8 = (r[6] | r[7] >> 8) & 63; if (r8 == 0) ez++;
r9 = (r[6] << 6 | r[7] >> 2) & 63; if (r9 == 0) ez++;
r10 = (r[7] << 4 | r[8] >> 4) & 63; if (r10 == 0) ez++;
r11 = (r[8] << 2 | r[9] >> 6) & 63; if (r11 == 0) ez++;
r12 = (r[9] | r[10] >> 8) & 63; if (r12 == 0) ez++;
r13 = (r[9] << 6 | r[10] >> 2) & 63; if (r13 == 0) ez++;
r14 = (r[10] << 4 | r[11] >> 4) & 63; if (r14 == 0) ez++;
r15 = (r[11] << 2 | r[12] >> 6) & 63; if (r15 == 0) ez++;
HLL_GET_REGISTER(reg,registers,j);
if (reg == 0) {
ez++;
E += 1; /* 2^(-reg[j]) is 1 when m is 0. */
} else {
E += PE[reg]; /* Precomputed 2^(-reg[j]). */
/* Additional parens will allow the compiler to optimize the
* code more with a loss of precision that is not very relevant
* here (floating point math is not commutative!). */
E += (PE[r0] + PE[r1]) + (PE[r2] + PE[r3]) + (PE[r4] + PE[r5]) +
(PE[r6] + PE[r7]) + (PE[r8] + PE[r9]) + (PE[r10] + PE[r11]) +
(PE[r12] + PE[r13]) + (PE[r14] + PE[r15]);
r += 12;
}
} else {
for (j = 0; j < REDIS_HLL_REGISTERS; j++) {
unsigned long reg;
HLL_GET_REGISTER(reg,registers,j);
if (reg == 0) {
ez++;
E += 1; /* 2^(-reg[j]) is 1 when m is 0. */
} else {
E += PE[reg]; /* Precomputed 2^(-reg[j]). */
}
}
}
/* Muliply the inverse of E for alpha_m * m^2 to have the raw estimate. */
@ -376,7 +412,7 @@ void hllCountCommand(redisClient *c) {
if (o == NULL) {
/* No key? Cardinality is zero since no element was added, otherwise
* we would have a key as HHLADD creates it as a side effect. */
* we would have a key as HLLADD creates it as a side effect. */
addReply(c,shared.czero);
} else {
/* Key exists, check type */