7zip update

[avitar]

​7-Zip 20.01 alpha was released.7-Zip for 64-bit Windows x64:
https://7-zip.org/a/7z2001-x64.exe
7-Zip for 32-bit Windows:
https://7-zip.org/a/7z2001.exe
What's new after 7-Zip 20.00 alpha:

• The default number of LZMA2 chunks per solid block in 7z archive was increased to 64.
  It allows to increase the compression speed for big 7z archives, if there is a big number
  of CPU cores and threads.
• The speed of PPMd compressing/decompressing was increased for 7z/ZIP/RAR archives.
• The new -ssp switch. If the switch -ssp is specified, 7-Zip doesn't allow the system
  to modify "Last Access Time" property of source files for archiving and hashing operations.
• Some bugs were fixed.
• New localization: Swahili.

See later update 2002 below!

[danlock]

A small fix to 7-Zip 20.01 was posted.

Source of following text: https://sourceforge.net/p/sevenzip/d...ad/9dbfea1e30/

---

7-Zip 20.02 alpha was released.

7-Zip for 64-bit Windows x64: https://7-zip.org/a/7z2002-x64.exe
7-Zip for 32-bit Windows: https://7-zip.org/a/7z2002.exe

What's new after 7-Zip 20.00 alpha:
[. . .]

Notes about changes in 7-Zip 20.02

[The] 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 20.02 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 [the source forum thread given above] to show the changes between 7-Zip 20.00 and new 7-Zip 20.02.

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.

[The] following command is a benchmark command that can show some changes of new version 20.02:

7z b -mmt=* -mm=* -bt > b.txt

The only expected changes in benchmark results between 20.00 and 20.02 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 20.02:

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 20.02 can be faster than 20.00, if your CPU has big number of threads.

What's new after 7-Zip 20.01 alpha: the bug was fixed: 7-Zip File Manager 20.01 could lock archive files while 7-Zip File Manager is running.

[Mike]

7-Zip 21.00 alpha was released:
https://sourceforge.net/p/sevenzip/d...ad/dd4edab390/