[Xapian-devel] Optimized VSEncoding

[Hurricane Tong]

Hi,


I optimized the code of VSEncoder,
and encode/decode the whole list, linux.postlist.


Encoding time :  
VSEncoder 103429ms
InterpolativeEncoder 684ms


Decoding time:
VSDecoder 756ms
InterpolativeDecoder 925ms


( compile with -o2, and the Interpolative Encoder/Decoder is just from the Xapian's code, bitstream.cc )


VS algorithm performs better in decoding, at the price of encoding time.


I analyse the VSEncoder, most time is spent on getting the optimal split, I try to do some optimization, but it seems very difficult to make significant progress.


I don't think the position list of a term will be frequently modified, so I think it is acceptable to sacrifice some encoding time for faster decoding.




------------------
Shangtong Zhang,Second Year Undergraduate,
School of Computer Science,
Fudan University, China.
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