Conclusions: same as above, except that 7-Zip decompression was especially slow here. Anyway, I saw that 7-Zip switched to a 64MB dictionary and a word size of 64 when I chose Ultra compression, so I went with those changes 7-Zip said they would require only 4413MB of RAM. As already noted, that had not happened here nothing new was running. It seemed that 7-Zip would stall halfway through a compression, if some other program grabbed some of the available RAM. It appeared that WinRAR’s interpretation might be that a 1024MB dictionary would be used as long as sufficient RAM was available, and otherwise the program would drop back to a smaller dictionary, but I was not sure whether that was the explanation. I was not sure why WinRAR seemed to work on this system with a 1024MB dictionary, while 7-Zip indicated that it would need 8472MB of RAM even for a 256MB dictionary nor was I sure why this error had arisen only now. 7-Zip: stalled with an error, after some minutes of trying: “The system cannot allocate the required amount of memory.” (I was not sure how long the program sat with that error message displayed, because the error came up under my browser, and there was no flashing taskbar notification.) The problem seemed to be in the dictionary size. Four large PDFs produced by Adobe Acrobat, totaling 3.47GB. WinRAR: 9:09 > 3.44GB (99%) 0:35.Ten large MP3 files (each 2-channel, 32 KHz, 256 Kbps CBR), totaling 1.36GB.Conclusions: it was probably not worth compressing these JPGs but if I did compress them, WinRAR compressed and decompressed as well as 7-Zip, at a much higher speed. 97% of original size) 0:02 to decompress. WinRAR: 0:16 to compress into a 187MB file (i.e.
Newer versions of WinRAR would confusingly offer RAR (rather than RAR5) as the latest version, with RAR4 as the legacy alternative.)įor 7-Zip, I started with 7z format, Ultra compression, LZMA2 (the default) (chosen because of 7-Zip’s limitation on options if I chose LZMA), 1024MB dictionary, word size = 256 bytes, non-solid, 6/8 CPU threads (so that it would not completely dominate the system), delete after compression. (Later, I would find that a 32MB setting seemed to be considered optimal for the dictionary. For WinRAR, I chose RAR5, Best compression method, 1024MB dictionary, no options other than delete after compression. I began by choosing what I thought would be optimal for each. (Of course, that would not work if the user had configured WinRAR not to be available via the context menu.)īoth 7-Zip and WinRAR offered multiple configuration options. In a recent version of WinRAR, I found relevant settings by going into Windows Explorer > select a file > right-click > WinRAR > Add to Archive. This discussion includes references to WinRAR’s settings. (Note also a later post discussing security in 7-Zip, another post offering some WinRAR benchmarks, and a different post reviewing Windows native compression.) In that search, I decided to compare WinRAR 圆4 5.40 against 7-Zip 圆4 16.02.