Use QBENCHMARK_ONCE rather than QBENCHMARK to avoid skewing the results:
when the QBENCHMARK block is repeated multiple times after the setup
code above runs once, only the first setFilterRegularExpression() call
unfilters some rows, while the subsequent calls simply check that there
is nothing to do.
The added benchmark is sensitive to the inefficiency - quadratic rather
than linear time complexity - fixed by
7d92ef63d7. The following two tables
contain the benchmark results on my GNU/Linux system. The numbers denote
milliseconds per iteration.
1. Qt 5.15.2 without the performance fix:
10K 25K 50K 100K 250K 500K
no match 0 1 2 5 14 28
all 0 0 0 1 3 7
first 0 1 2 5 14 28
1000th 2 6 12 25 68 302
middle 3 34 132 518 3300 13665
1000th from end 1 4 9 19 50 103
last 0 1 2 5 14 30
each 10'000th 0 39 211 937 6326 41050
each 100'000th 0 1 2 5 4226 34780
Without the fix the benchmark times out and aborts at 1000K and 2000K
data rows.
2. Qt 5.15.2 with the performance fix:
10K 25K 50K 100K 250K 500K 1000K 2000K
no match 0 1 2 4 12 26 56 136
all 0 0 0 1 3 7 14 28
first 0 1 2 4 12 26 56 136
1000th 0 1 2 4 13 28 62 145
middle 0 1 2 4 13 27 59 142
1000th from end 0 1 2 4 13 28 60 145
last 0 1 2 4 13 27 59 141
each 10'000th 0 1 2 6 22 69 290 1413
each 100'000th 0 1 2 4 13 30 81 261
Change-Id: I419a5521dd0be7676fbb09b34b4069d4a76423b1
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
7c9597ef56