[Xapian-tickets] [Xapian] #782: Improve encode_length() performance

[Xapian]

#782: Improve encode_length() performance
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 Reporter:  Kronuz          |             Owner:  olly
     Type:  enhancement     |            Status:  new
 Priority:  normal          |         Milestone:
Component:  Backend-Remote  |           Version:
 Severity:  minor           |        Resolution:
 Keywords:                  |        Blocked By:
 Blocking:                  |  Operating System:  All
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Comment (by olly):

 I realised I had stupidly cut-and-pasted the loop above verbatim into both
 versions.  With the appropriate function called in each case I'm seeing
 ~1400ns vs ~1200ns for the `s +=` version.  Not sure why fixing one
 version changes the timings for the unchanged one substantially though.
 Maybe I should heed those `***WARNING***` messages.

 > Maybe not as dramatic, but still faster. And "optimized" code is clean,
 imvho, nothing eccentric or esoteric; and generated instructions (at least
 for x86_64) promote processor pipelining and easy branch prediction.

 I'm not arguing against optimising this - just trying to make sure we're
 optimising based on valid data.

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Ticket URL: <https://trac.xapian.org/ticket/782#comment:6>
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