[HUF] Improve Huffman encoding speed #2733
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Improve Huffman encoding speed by 20% for gcc and 10% for clang. | Compiler | Benchmark | Config | Dataset | Ratio | Speed MB/s (dev) | Speed MB/s (huf-cspeed) | Speed MB/s (huf-cspeed - dev) | |----------|-------------------|---------|-------------|-------|------------------|-------------------------|-------------------------------| | gcc | compress | level_1 | enwik7 | 2.43 | 253.70 | 258.72 | 2.0% | | gcc | compress | level_1 | silesia | 2.88 | 341.90 | 348.15 | 1.8% | | gcc | compress_literals | level_1 | enwik7 | 1.49 | 761.83 | 912.76 | 19.8% | | gcc | compress_literals | level_1 | silesia | 1.28 | 754.83 | 902.37 | 19.5% | | gcc | compress_literals | level_7 | enwik7 | 1.29 | 502.81 | 552.79 | 9.9% | | gcc | compress_literals | level_7 | silesia | 1.11 | 675.97 | 776.44 | 14.9% | | clang | compress | level_1 | enwik7 | 2.43 | 277.54 | 280.98 | 1.2% | | clang | compress | level_1 | silesia | 2.88 | 369.98 | 375.46 | 1.5% | | clang | compress_literals | level_1 | enwik7 | 1.49 | 828.83 | 918.41 | 10.8% | | clang | compress_literals | level_1 | silesia | 1.28 | 815.81 | 905.41 | 11.0% | | clang | compress_literals | level_7 | enwik7 | 1.29 | 533.13 | 553.30 | 3.8% | | clang | compress_literals | level_7 | silesia | 1.11 | 714.52 | 775.38 | 8.5% |
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Tests are passing now (except for the 6 that are killed by GitHub actions) |
Cyan4973
reviewed
Jul 30, 2021
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| /** HUF_CStream_t: | ||
| * Huffman uses its own BIT_CStream_t implementation. | ||
| * There are three major differences from BIT_CStream_t: |
Cyan4973
approved these changes
Jul 30, 2021
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* Add a Huffman round trip fuzzer
* Fix two minor bugs in Huffman that aren't exposed in zstd
- Incorrect weight comparison (weights are allowed to be equal to
table log).
- HUF_compress1X_usingCTable_internal() can return compressed
size >= source size, so the assert that `cSize <= 65535` isn't
correct, and it needs to be checked instead.
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Improve Huffman encoding speed by 20% for gcc and 10% for clang.
compressbenchmark measures total compression speed.compress_literalsbenchmark compresses the file at the given level. It then extracts the literals from the compressed frame. Then it measures the speed of literal compression on each block of extracted literals.I also added a new Huffman round trip fuzzer in the 2nd commit. It found two minor bugs in Huffman compression that cannot be triggered in zstd. I've run it for a few million iterations and it looks good so far.