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//
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//
#include "standardpch.h"
#include "cycletimer.h"
CycleTimer::CycleTimer()
{
start = 0;
stop = 0;
overhead = QueryOverhead();
}
CycleTimer::~CycleTimer()
{
}
void CycleTimer::Start()
{
BOOL retVal = QueryThreadCycleTime(GetCurrentThread(), &start);
if (retVal == FALSE)
{
LogError("CycleTimer::Start unable to QPC. error was 0x%08x", ::GetLastError());
::__debugbreak();
}
}
void CycleTimer::Stop()
{
BOOL retVal = QueryThreadCycleTime(GetCurrentThread(), &stop);
if (retVal == FALSE)
{
LogError("CycleTimer::Stop unable to QPC. error was 0x%08x", ::GetLastError());
::__debugbreak();
}
}
unsigned __int64 CycleTimer::GetCycles()
{
return stop - start - overhead;
}
unsigned __int64 CycleTimer::QueryOverhead()
{
unsigned __int64 tot = 0;
unsigned __int64 startCycles;
unsigned __int64 endCycles;
const int N = 1000;
for (int i = 0; i < N; i++)
{
QueryThreadCycleTime(GetCurrentThread(), &startCycles);
QueryThreadCycleTime(GetCurrentThread(), &endCycles);
tot += (endCycles - startCycles);
}
return tot / N;
}
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