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931441251e
Specific platforms (e.g. TDM-GCC) can have terrible timer resolution, and our checking code will then loop for an inordinate amount of time. This change will make it so that the calibration gives up after 3 seconds and just uses the already measured values. This leaves one open question, how to signal that the resolution is terrible and benchmarking should not happen? Fixes #1237
73 lines
2.4 KiB
C++
73 lines
2.4 KiB
C++
/*
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* Created by Phil on 05/08/2013.
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* Copyright 2013 Two Blue Cubes Ltd. All rights reserved.
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*
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* Distributed under the Boost Software License, Version 1.0. (See accompanying
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* file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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*/
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#include "catch_timer.h"
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#include <chrono>
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static const uint64_t nanosecondsInSecond = 1000000000;
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namespace Catch {
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auto getCurrentNanosecondsSinceEpoch() -> uint64_t {
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return std::chrono::duration_cast<std::chrono::nanoseconds>( std::chrono::high_resolution_clock::now().time_since_epoch() ).count();
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}
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auto estimateClockResolution() -> uint64_t {
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uint64_t sum = 0;
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static const uint64_t iterations = 1000000;
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auto startTime = getCurrentNanosecondsSinceEpoch();
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for( std::size_t i = 0; i < iterations; ++i ) {
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uint64_t ticks;
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uint64_t baseTicks = getCurrentNanosecondsSinceEpoch();
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do {
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ticks = getCurrentNanosecondsSinceEpoch();
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} while( ticks == baseTicks );
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auto delta = ticks - baseTicks;
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sum += delta;
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// If we have been calibrating for over 3 seconds -- the clock
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// is terrible and we should move on.
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// TBD: How to signal that the measured resolution is probably wrong?
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if (ticks > startTime + 3 * nanosecondsInSecond) {
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return sum / i;
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}
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}
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// We're just taking the mean, here. To do better we could take the std. dev and exclude outliers
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// - and potentially do more iterations if there's a high variance.
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return sum/iterations;
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}
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auto getEstimatedClockResolution() -> uint64_t {
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static auto s_resolution = estimateClockResolution();
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return s_resolution;
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}
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void Timer::start() {
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m_nanoseconds = getCurrentNanosecondsSinceEpoch();
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}
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auto Timer::getElapsedNanoseconds() const -> uint64_t {
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return getCurrentNanosecondsSinceEpoch() - m_nanoseconds;
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}
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auto Timer::getElapsedMicroseconds() const -> uint64_t {
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return getElapsedNanoseconds()/1000;
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}
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auto Timer::getElapsedMilliseconds() const -> unsigned int {
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return static_cast<unsigned int>(getElapsedMicroseconds()/1000);
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}
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auto Timer::getElapsedSeconds() const -> double {
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return getElapsedMicroseconds()/1000000.0;
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}
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} // namespace Catch
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