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Notes about changes in 7-Zip 20.01
Te size of solid block for 7z/LZMA2 archives was increased, so 7-Zip can use more threads and chunks to compress solid block. It can improve the compression speed for multi-core processors like Threadripper/Epyc and Xeon. Also it can slightly improve multi-core LZMA2 decompression speed.
Some important parts of PPMd code were rewritten for faster compression and decompression.
And that new PPMd code works faster for data that is not too compressible, like exe files or already compressed data.
Also PPMD in previous 7-Zip could be slow in some Intel CPUs for decompression, if CVE-2018-3639 Speculative Store Bypass (SSB) mitigation was enabled in system. And new PPMd code must work faster for such cases too.
Another change of 7-Zip 20.01 is speed optimization in Delta filter code, that is about two times faster than in previous version.
7-Zip testing
You can post the results of tests to this forum thread to show the changes between 7-Zip 20.00 and new 7-Zip 20.01.
Notes: you can test any version of 7-Zip without full installation.
You just need to extract exe installer of 7-Zip as archive file to any folder and run 7-zip from that folder.
Tne following command is a benchmark command that can show some changes of new version 20.01:
7z b -mmt=* -mm=* -bt > b.txt
The only expected changes in benchmark results between 20.00 and 20.01 versions are PPMd and Delta lines.
If you have CPU with big number of threads, you can compare 7z/LZMA2 compression speed for big data (more than 4 GB) with versions 20.00 and 20.01:
7z a mx1.7z files -bt -mx1 >> a.txt
7z t mx1.7z -bt >> a.txt
7z a mx5.7z files -bt -mx5 >> a.txt
7z t mx5.7z -bt >> a.txt
7-Zip 20.01 can be faster than 20.00, if your CPU has big number of threads.
Last edit: Igor Pavlov 2 days ago
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