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deflate_compress: improve block splitting in near-optimal compressor

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When choosing which literals and matches to use for the block split
statistics in deflate_compress_near_optimal(), take into account the
min_len heuristic.  This should give slightly more accurate results.
This commit is contained in:
Eric Biggers 2022-01-04 21:25:56 -08:00
parent ea536bcce2
commit 074ef7db98
1 changed files with 5 additions and 1 deletions
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6
lib/deflate_compress.c
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@ -3362,8 +3362,12 @@ deflate_compress_near_optimal(struct libdeflate_compressor * restrict c,
const u8 * const in_max_block_end = choose_max_block_end( const u8 * const in_max_block_end = choose_max_block_end(
in_next, in_end, SOFT_MAX_BLOCK_LENGTH); in_next, in_end, SOFT_MAX_BLOCK_LENGTH);
const u8 *next_observation = in_next; const u8 *next_observation = in_next;
unsigned min_len;
deflate_near_optimal_begin_block(c, in_block_begin == in); deflate_near_optimal_begin_block(c, in_block_begin == in);
min_len = calculate_min_match_len(in_next,
in_max_block_end - in_next,
c->max_search_depth);
/* /*
* Find matches until we decide to end the block. We end the * Find matches until we decide to end the block. We end the
@ -3421,7 +3425,7 @@ deflate_compress_near_optimal(struct libdeflate_compressor * restrict c,
} }
c->freqs.litlen[*in_next]++; c->freqs.litlen[*in_next]++;
if (in_next >= next_observation) { if (in_next >= next_observation) {
if (best_len >= 4) { if (best_len >= min_len) {
observe_match(&c->split_stats, observe_match(&c->split_stats,
best_len); best_len);
next_observation = in_next + best_len; next_observation = in_next + best_len;