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bench: Fix subtle counting issue when rescaling iteration count

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Make sure that the count is a zero modulo the new mask before
scaling, otherwise the next time until a measure triggers
will take only 1/2 as long as accounted for. This caused
the 'min time' to be potentially off by as much as 100%.
This commit is contained in:
Wladimir J. van der Laan 2016-11-22 09:59:50 +01:00
parent e4dbeb9499
commit e0a9cb25b0
1 changed files with 5 additions and 2 deletions
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7
src/bench/bench.cpp
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@ -64,8 +64,11 @@ bool State::KeepRunning()
return true; return true;
} }
if (elapsed*16 < maxElapsed) { if (elapsed*16 < maxElapsed) {
countMask = ((countMask<<1)|1) & ((1LL<<60)-1); uint64_t newCountMask = ((countMask<<1)|1) & ((1LL<<60)-1);
countMaskInv = 1./(countMask+1); if ((count & newCountMask)==0) {
countMask = newCountMask;
countMaskInv = 1./(countMask+1);
}
} }
} }
lastTime = now; lastTime = now;