Bulat_Ziganshin
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небольшие пояснения о новой версии SREP:
-m1 works like 1.0. there are some internal changes because i used common codebase with -m2, and seems it resulted in decreased speed of 32-bit version and increased speed of 64-bit one, compared to 1.0
-m2 is a new approach. while -m1 stores SHA1 hash for every 512-byte block and detect matches by comparing SHA1 hash of current block with stored ones, -m2 doesn't store SHA1 (thus much less memory usage) but rereads old parts of file and performs direct data comparison. so, peculiarities of -m2 are:
* less memory (2-3% for -m2 vs 6-7% for -m1)
* OS disk cache is intensively used
* 100% reliable match checking
* file to compress cannot be read from stdin
* less CPU time used, but much more OS calls and disk operations
overall, i recommend you to use 64-bit version in default -m2 mode and don't mind about all those differences. compression ratio should be almost the same
small test of my own (compressing cached file):
SREP 1.0
D:\testing>srep dll700.dll nul
42 mb used for hash
Compression ratio: 690514620 -> 390647716: 56.57%. Cpu 32.427 mb/sec, real 33.322 mb/sec
D:\testing>srep64 dll700.dll nul
42 mb used for hash
Compression ratio: 690514620 -> 390647716: 56.57%. Cpu 40.203 mb/sec, real 39.570 mb/sec
SREP 1.5
D:\testing>C:\!\FreeArchiver\Compression\SREP\srep32i.exe -m1 dll700.dll nul
39 mb used for hash
Compression ratio: 690514620 -> 390644072: 56.57%. Cpu 32.788 mb/sec, real 34.288 mb/sec
D:\testing>C:\!\FreeArchiver\Compression\SREP\srep64i.exe -m1 dll700.dll nul
39 mb used for hash
Compression ratio: 690514620 -> 390644072: 56.57%. Cpu 40.021 mb/sec, real 41.242 mb/sec
D:\testing>C:\!\FreeArchiver\Compression\SREP\srep32i.exe dll700.dll nul
14 mb used for hash
Compression ratio: 690514620 -> 390644072: 56.57%. Cpu 43.438 mb/sec, real 44.389 mb/sec
D:\testing>C:\!\FreeArchiver\Compression\SREP\srep64i.exe dll700.dll nul
14 mb used for hash
Compression ratio: 690514620 -> 390644072: 56.57%. Cpu 58.705 mb/sec, real 56.447 mb/sec |
(шутка) Пока весь механизм работы с профилями в разработке.