I am using 7z v9.25, and I noticed that if I select the combo archive format=ZIP and compression method=BZIP2, I am only using 1 core (25% cpu usage with an I5 processor).
I was almost sure that multithreading was possible in this combo, and checked another computer where I had this set up and working (99% cpu with 32 cores). I noticed that this computer had 7x v9.20 instead of v9.25.
So my question: is there any reason for this combo to stop multithreading? I've compressed a text file with both versions, and the output is the same (same CRC), only the v9.20 finished significantly faster.
I've tried also with v9.28, having the same behaviour as v9.25.
Thanks for reporting about that BUG!
It uses one thread, if you compress just one file to ZIP archive with bzip2 method.
I'll fix that BUG in next version.
In current version you can write in Parameters:
and it will use 4 threads.
Thanks for the workaround, I will try it :). It was indeed a single file (a 4Gb one, so multithreading was really useful there).
And thanks for your great work, 7z is a must-have-tool who has replaced winrar for me :)