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| author | Giorgio Vazzana <mywing81@gmail.com> | 2013-05-18 13:53:52 +0200 |
|---|---|---|
| committer | Michael Niedermayer <michaelni@gmx.at> | 2013-05-20 04:27:34 +0200 |
| commit | d0a34aeedff187873e1b42e0902d9dfbba08a1f4 (patch) | |
| tree | ff7decbc6941a6e51dc4f7f99e6f00b82b703f1a | |
| parent | b7be8ea92a4b23de5d622097ba451c4b266e6563 (diff) | |
| download | ffmpeg-d0a34aeedff187873e1b42e0902d9dfbba08a1f4.tar.gz | |
md5: optimize second round by using 4-operation form of G()
4-operation form is preferred over 3-operation because it breaks a long
dependency chain, thus allowing a superscalar processor to execute more
operations in parallel.
The idea was taken from: http://www.zorinaq.com/papers/md5-amd64.html
AMD Athlon(tm) II X3 450 Processor, x86_64
$ for i in $(seq 1 4); do ./avutil_md5_test2; done
size: 1048576 runs: 1024 time: 5.821 +- 0.019
size: 1048576 runs: 1024 time: 5.822 +- 0.019
size: 1048576 runs: 1024 time: 5.841 +- 0.018
size: 1048576 runs: 1024 time: 5.821 +- 0.018
$ for i in $(seq 1 4); do ./avutil_md5_test2; done
size: 1048576 runs: 1024 time: 5.646 +- 0.019
size: 1048576 runs: 1024 time: 5.646 +- 0.018
size: 1048576 runs: 1024 time: 5.642 +- 0.019
size: 1048576 runs: 1024 time: 5.641 +- 0.019
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
| -rw-r--r-- | libavutil/md5.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/libavutil/md5.c b/libavutil/md5.c index 7375ce55a5..e3c4981217 100644 --- a/libavutil/md5.c +++ b/libavutil/md5.c @@ -84,7 +84,7 @@ static const uint32_t T[64] = { // T[i]= fabs(sin(i+1)<<32) \ if (i < 32) { \ if (i < 16) a += (d ^ (b & (c ^ d))) + X[ i & 15]; \ - else a += (c ^ (d & (c ^ b))) + X[(1 + 5*i) & 15]; \ + else a += ((d & b) | (~d & c))+ X[(1 + 5*i) & 15]; \ } else { \ if (i < 48) a += (b ^ c ^ d) + X[(5 + 3*i) & 15]; \ else a += (c ^ (b | ~d)) + X[( 7*i) & 15]; \ |