PMT - Parallel Multithreaded Encoder/Decoder

[KaktoR]

mpz with PMT
Compressed 64 files, 209,434,083 => 180,728,551 bytes. Ratio 86.29%
Compression time: cpu 0.20 sec/real 38.46 sec = 1%. Speed 5.45 mB/s

Tested 64 files, 180,728,551 => 209,434,083 bytes. Ratio 86.29%
Testing time: cpu 0.19 sec/real 36.54 sec = 1%. Speed 5.73 mB/s

mpz only
Compressed 64 files, 209,434,083 => 180,670,089 bytes. Ratio 86.27%
Compression time: cpu 0.30 sec/real 103.93 sec = 0%. Speed 2.02 mB/s

Tested 64 files, 180,670,089 => 209,434,083 bytes. Ratio 86.27%
Testing time: cpu 0.36 sec/real 95.90 sec = 0%. Speed 2.18 mB/s

Tested with settings -b64m -t100p for encode/decode with a Ryzen 5 2600 (12 threads).

I just wonder why ratio is a little bit better without pmt