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

[Xapian]

#782: Improve encode_length() performance
----------------------------+-------------------------
 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
----------------------------+-------------------------

Comment (by olly):

 Curiously I don't see nearly as much of a speed-up on x86 Linux:

 {{{
 2019-05-05 18:04:29
 Running ./benchmark-encode_length
 Run on (8 X 3700 MHz CPU s)
 CPU Caches:
   L1 Data 32K (x4)
   L1 Instruction 32K (x4)
   L2 Unified 256K (x4)
   L3 Unified 6144K (x1)
 ***WARNING*** CPU scaling is enabled, the benchmark real time measurements
 may be noisy and will incur extra overhead.
 ***WARNING*** Library was built as DEBUG. Timings may be affected.
 -----------------------------------------------------------------
 Benchmark                          Time           CPU Iterations
 -----------------------------------------------------------------
 BM_EncodeLength_Original         957 ns        957 ns     725154
 BM_EncodeLength_Optimized        752 ns        752 ns     914252
 }}}

 I had to comment out the `BENCHMARK_MAIN();` as otherwise linking fails
 with multiple definitions of `main`, but otherwise that's the same code
 you show and the same compilation command.

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Ticket URL: <https://trac.xapian.org/ticket/782#comment:2>
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