ConorStokes
commented
8 years ago Thanks for the thorough analysis! gcc does seem to have a problem generating tight code for LZSSE, although I'm surprised Intel is that far ahead! I'll have to have a more thorough look at the assembly you generated on the weekend to see what is causing the slowdown (although I suspect you are right and the Intel code is doing a much better job with the registers).
I'd say that the slow result with the small file alice29 could be due to timer resolution or it could be due to some fixed overhead/system overhead. One thing I've found is that if the OS hasn't allocated the memory pages for the buffer yet (just mapped them), then the initial page fault to allocate memory can be quite a large amount of overhead on those small files.
Sanmayce
Hi Conor, many thanks for the undreamt performance of your LZSSE2, simply the FASTEST decompressor!
Not an issue but feedback, wish this site had [Feedback] section as well. My wish was to have LZSSE2 in form of console tool as well, so I attempted to do so, but not as it had to be, your etude - your tool, that's the right combination, however I wanted level 17 in my textual comparisons so I just embedded LZSSE2 into my fastest (old, 1MB sliding window) Nakamichi, the result:
LZSSE2 excels at:
Overall, significantly better everywhere, LZSSE2 is superior to Tengu, hands down. In my benchmarks with Hamid's TurboBench from (Feb 21), LZSSE2 level 16 decompresses 2x faster than Nakamichi 'Goldenboy'! However with Haswell and above I expect 3x, even 4x. For more tests (console dumps), you may see my compression logs/notes (far from finished) at: www.sanmayce.com/Downloads/The-Last-Stand_booklet.pdf
Also, in the www.sanmayce.com/Downloads/TEXTUAL_MADNESS.zip package I made one .bat file running 12 compressors for a given file, thus giving quick look where one is ranked:
Performers:
Level17 gives excellent tightness and incredible decompression speed (i5-2430M @3GHz, DDR3 @666MHz):
The SSE4.1 and AVX .cod files are included (Assembly, that is), do you see register utilization/distribution as you intended? In AVX code I see 4466 lines for LZSSE2_Decompress procedure, while the SSE4.1 amounts to 4819, how does this translate into speed, say, on Haswell? On i5-2430M @3GHz, DDR3 @666MHz I see no speed difference, at all:
And to mix Level 17 with the TurboBench' results:
Very strange, decompression speed differs a lot between Hamid's bench and mine, my trials are 64, with 'dickens' Intel 15.0 is 2x faster than GCC 5.3.0, or I am wrong?! Also, no clue, why with 'alice29' my bench gives the miserable 53 MB/s whereas TurboBench reports 1810.58MB/s?! That's why told you that my knowledge is inferior, I failed to offer reliable bench. Maybe, I will change clock() with:
I still don't understand, even partially, the decompression code, yet, at first glance the code generated by Intel 15.0 is tight and makes full use of registers, no?!
Cannot say keep up the fantastic work since you made good already.
Best, Sanmayce