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Remove dead code from PredictNumItersNeeded (#1206)

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* Remove `min` with dead path.

When `isSignificant` is false, the smallest value `multiplier` can
approach is 14. Thus, min(10, multiplier) will always return 10.

Addresses part one of #1205.

* Remove always false condition.

   1. `multiplier <= 1.0` implies `i.seconds >= min_time * 1.4`
   2. By (1), `isSignficant` is true because `i.seconds > min_time * 1.4` implies `i.seconds > min_time` implies that `i.seconds / minTime > 1 > 0.1`. Thus, the ternary maintains the same multiplier value.
   3. `ShouldReportResults` is always called before `PredictNumItersNeeded`, if `i.seconds >= min_time` then the loop is broken and `PredictNumItersNeeded` is never called.
   4. 1 and 3 together imply that `multiplier <= 1.0` is never true.

Addresses part 2 of #1205.
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Braedy 2021-07-29 01:59:46 -06:00 committed by GitHub
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src/benchmark_runner.cc
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@ -239,8 +239,7 @@ IterationCount BenchmarkRunner::PredictNumItersNeeded(
// NOTE: When the last run was at least 10% of the min time the max
// expansion should be 14x.
bool is_significant = (i.seconds / min_time) > 0.1;
multiplier = is_significant ? multiplier : std::min(10.0, multiplier);
if (multiplier <= 1.0) multiplier = 2.0;
multiplier = is_significant ? multiplier : 10.0;
// So what seems to be the sufficiently-large iteration count? Round up.
const IterationCount max_next_iters = static_cast<IterationCount>(