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Reduce fdiv's into fmul's

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Provides small speedup on microarchitectures where the floating
point divide is slower than the floating point multiply.
This commit is contained in:
Mahesh Madhav 2024-10-05 05:40:19 +00:00 committed by Eugene Kliuchnikov
parent f25050c0d0
commit cefec3ce9d
3 changed files with 5 additions and 4 deletions
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2
c/enc/block_splitter_inc.h
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@ -129,7 +129,7 @@ static size_t FN(FindBlocks)(const DataType* data, const size_t length,
}
/* More blocks for the beginning. */
if (byte_ix < 2000) {
block_switch_cost *= 0.77 + 0.07 * (double)byte_ix / 2000;
block_switch_cost *= 0.77 + 0.00003 * (double)byte_ix;
}
for (k = 0; k < num_histograms; ++k) {
cost[k] -= min_cost;

5
c/enc/encode.c
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@ -437,10 +437,11 @@ static BROTLI_BOOL ShouldCompress(
if ((double)num_literals > 0.99 * (double)bytes) {
uint32_t literal_histo[256] = { 0 };
static const uint32_t kSampleRate = 13;
static const double invKSampleRate = 1.0 / 13.0;
static const double kMinEntropy = 7.92;
const double bit_cost_threshold =
(double)bytes * kMinEntropy / kSampleRate;
size_t t = (bytes + kSampleRate - 1) / kSampleRate;
(double)bytes * kMinEntropy * invKSampleRate;
size_t t = (bytes + kSampleRate - 1) * invKSampleRate;
uint32_t pos = (uint32_t)last_flush_pos;
size_t i;
for (i = 0; i < t; i++) {

2
c/enc/literal_cost.c
View File

@ -121,7 +121,7 @@ static void EstimateBitCostsForLiteralsUTF8(size_t pos, size_t len, size_t mask,
rapidly in the beginning of the file, perhaps because the beginning
of the data is a statistical "anomaly". */
if (i < 2000) {
lit_cost += 0.7 - ((double)(2000 - i) / 2000.0 * 0.35);
lit_cost += 0.7 - ((double)(2000 - i) * 0.000175);
}
cost[i] = (float)lit_cost;
}