Unpredictable compression speed using "--optimal" level#11

BriefLZ compression speed with "--optimal" varies wildly depending on input data. I used "blzpack --optimal" to compress several biological datasets. Most of time it compresses at speed of about 1 to 3 MB/s (sometimes 6). However, when compressing human genome, its speed dropped to 33 kB/s. I tried it twice, both time it took ~27 hours to complete. In case if this is normal and expected behaviour, I think it should be documented, so that users know the risks of using "--optimal" mode. blzpack seems to works fine with other settings. I used BriefLZ 1.3.0, commit 0ab07a5, built using instructions from readme. I used only default block size so far, though I plan to test it with other block sizes too. Test machine: Ubuntu 18.04.1 LTS, dual Xeon E5-2643v3, 128 MB RAM, no other tasks running. This test was a part of Sequence Compression Benchmark: http://kirr.dyndns.org/sequence-compression-benchmark/ - this website includes all test data, commands, and measurements. In particular, all test data is available at: http://kirr.dyndns.org/sequence-compression-benchmark/?page=Datasets Compression and decompression speed of the "blzpack --optimal" on all datasets: C-Speed (MB/s) | D-Speed (MB/s) | DataSize (MB) | DataName -------------------------|----------------------------|---------------|------------ 1.184 | 3.033 | 0.051 | Gordonia phage GAL1 GCF_001884535.1 2.526 | 24.85 | 0.522 | WS1 bacterium JGI 0000059-K21 GCA_000398605.1 3.069 | 54.70 | 1.712 | Astrammina rara GCA_000211355.2 3.116 | 108.8 | 5.809 | Nosema ceranae GCA_000988165.1 3.052 | 135.5 | 9.217 | Cryptosporidium parvum Iowa II GCA_000165345.1 3.152 | 151.1 | 13.14 | Spironucleus salmonicida GCA_000497125.1 3.153 | 172.3 | 23.67 | Tieghemostelium lacteum GCA_001606155.1 3.017 | 182.2 | 36.92 | Fusarium graminearum PH-1 GCF_000240135.3 0.990 | 209.8 | 56.15 | Salpingoeca rosetta GCA_000188695.1 6.379 | 237.9 | 67.61 | PDB 2.734 | 311.1 | 73.24 | Homo sapiens GRCh38 peptides all 3.273 | 228.8 | 106.4 | Chondrus crispus GCA_000350225.2 6.384 | 184.8 | 122.4 | NCBI Virus RefSeq Protein 2.903 | 256.0 | 245.3 | Mitochondrion 2.787 | 310.9 | 340.4 | UCSC hg38 7way knownCanonical-exonNuc 3.352 | 238.5 | 341.0 | Kappaphycus alvarezii GCA_002205965.2 0.216 | 482.0 | 481.8 | NCBI Virus Complete Nucleotide Human 0.840 | 505.8 | 610.3 | SILVA 132 LSURef 2.719 | 410.3 | 968.8 | UCSC hg38 20way knownCanonical-exonNuc 0.749 | 257.9 | 1008 | Strongylocentrotus purpuratus GCF_000002235.4 2.587 | 404.6 | 1109 | SILVA 132 SSURef Nr99 1.071 | 758.2 | 1215 | Influenza 2.812 | 252.6 | 2756 | Helicobacter 1.669 | 523.2 | 3282 | SILVA 132 SSURef 0.033 | 255.4 | 3313 | Homo sapiens GCA_000001405.28 Please let me know if you need any other details or help reproducing this issue.