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Add support for multithreading in encoder #1248

Merged
merged 2 commits into from
Oct 9, 2020
Merged

Add support for multithreading in encoder #1248

merged 2 commits into from
Oct 9, 2020

Commits on May 20, 2020

  1. Add multithreading support in the T1 (entropy phase) encoder 

    - API wise, opj_codec_set_threads() can be used on the encoding side
- opj_compress has a -threads switch similar to opj_uncompress
    @rouault
    rouault committed May 20, 2020
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  2. Add multithreaded support in the DWT encoder. 

    Update the bench_dwt utility to have a -decode/-encode switch

Measured performance gains for DWT encoder on a
Intel(R) Core(TM) i7-6700HQ CPU @ 2.60GHz (4 cores, hyper threaded)

Encoding time:
$ ./bin/bench_dwt -encode -num_threads 1
time for dwt_encode: total = 8.348 s, wallclock = 8.352 s

$ ./bin/bench_dwt -encode -num_threads 2
time for dwt_encode: total = 9.776 s, wallclock = 4.904 s

$ ./bin/bench_dwt -encode -num_threads 4
time for dwt_encode: total = 13.188 s, wallclock = 3.310 s

$ ./bin/bench_dwt -encode -num_threads 8
time for dwt_encode: total = 30.024 s, wallclock = 4.064 s

Scaling is probably limited by memory access patterns causing
memory access to be the bottleneck.
The slightly worse results with threads==8 than with thread==4
is due to hyperthreading being not appropriate here.
    @rouault
    rouault committed May 20, 2020
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