Optimized method not really optimized….

[sjan26s2]

I’m using the latest build of PowerArchiver 2016 16.00.69. I am the kind of person who loves the best compression possible within a fair time.
I have tested the 7-Zip option and have set it to Optimized method and Ultra (memory req.) compression and have solid archive enabled.
I expected this to give the best possible compression, but this is not so.
For example, on the following file “Ashampoo Anti-Virus 1.2.0.exe” which is 158,458 KB, I get the following results:

7-Zip (Optimized method) -> 159,945 KB
7-Zip (LZMA2 method + everything else same) -> 157,863 KB

I expected that the Optimized method would take into account the big initial file size and use the LZMA2 method to get the smallest possible compressed file.

Why isn’t that the case?

Also, just a suggestion. Put in an option that uses all methods automatically and performs the compression multiple times and then leaves you with the best compressed file possible for that format (7-Zip, RAR, CAB, etc).
For example, if I select to get smallest file with 7-Zip, it does the compression several times using the different methods and then leaves me with the smallest file it could end up with after its all been run.

[Mili]

confirmed and noted!

thanks for taking the time to provide the details

[sjan26s2]

Please provide updates as something more comes to light regarding this.

[nikkho]

Can confirm at least in 17.00 problem is fixed. Nevertheless, ratio on Optimized compression, is not as good as in the official 7-Zip, so I will fill a new post.

[spwolf]

try the same files with .pa format now

[nikkho]

I have compressed full PowerArchiver x64 portable in my SSD disk, so it is easy for you to reproduce.

• Uncompressed size: 176.473.679 bytes.
• 7-Zip 17.00 Ultra LZMA 128MB fb273 myx=9: 28.330.063 bytes.
• PowerArchiver 7z 17.00.69 LZMA Ultra: 29.060.624 bytes.
• 7-Zip 17.00 Ultra LZMA2 128MB fb273 myx=9: 28.323.572 bytes.
• PowerArchiver 17.00.69 7z LZMA2 Ultra: 29.062.095 bytes.
• PowerArchiver 17.00.69 7z Optimized Ultra: 41.579.382 bytes.

Take a look at the bad results with the Optimized profile, and also at the equivalent PA implementation, being slightly worse than the one in 7-Zip, meaning that the library used or its parameters, are subobtimal.

By the way, same with PA format, excellent results:

• PowerArchiver 17.00.69 pa Extreme Optimize Strong: 27.114.421 bytes.