According to my profiling of Qt Creator, qHash and the SHA-1 calculation
are the hottest spots remaining in QtCore. The current qHash function is
not really vectorizable. We could come up with a different algorithm
that is more SIMD-friendly, but since we have the CRC32 instruction that
can read 32- and 64-bit entities, we're set.
This commit also updates the benchmark for QHash and benchmarks both
the hashing function itself and the QHash class. The updated
benchmarks for the CRC32 on my machine shows that the hashing function
is *always* improved, but the hashing isn't always. In particular, the
current algorithm is better for the "numbers" case, for which the data
sample differs in very few bits. The new code is 33% slower for that
particular case.
On average, the improvement (including the "numbers" case) is:
compared to qHash only QHash
Qt 5.0 function 2.54x 1.06x
Qt 4.x function 4.34x 1.34x
Java function 2.71x 1.11x
Test machine: Sandybridge Core i7-2620M @ 2.66 GHz with turbo disabled
for the benchmarks
Change-Id: Ia80b98c0e20d785816f7a7f6ddf40b4b302c7297
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Change copyrights and license headers from Nokia to Digia
Change-Id: If1cc974286d29fd01ec6c19dd4719a67f4c3f00e
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
It's not faster under _any_ metric than the new algorithm, and it loses a lot of
spread which is a bad thing.
Change-Id: Ic87258f1c887822ffea1cb1517355564fabc3c26
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>
We must do this the same way we do all other hash algorithms for fair
comparison, as otherwise, the call to the PLT unfairly penalises
QHash<QString>'s results, as it's in a different shared object.
Change-Id: I69c891f5a97dcccdfcfbdbf32796f86242a42963
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
As in the past, to avoid rewriting various autotests that contain
line-number information, an extra blank line has been inserted at the
end of the license text to ensure that this commit does not change the
total number of lines in the license header.
Change-Id: I311e001373776812699d6efc045b5f742890c689
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>
main.cpp is easier for my muscle memory to remember than qhash_string as it is
used by a number of other tests.
Change-Id: I044f995d55a4ff1328dde0ae27b6e36a80114c38
Reviewed-by: Richard J. Moore <rich@kde.org>
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>
Thiago Macieira
Sergio Ahumada
Iikka Eklund
Robin Burchell
Jason McDonald
Robin Burchell