357 lines
8.7 KiB
C++
357 lines
8.7 KiB
C++
/*-------------------------------------------------------------------------
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* drawElements C++ Base Library
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* -----------------------------
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*
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* Copyright 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*//*!
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* \file
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* \brief Cross-thread barrier.
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*//*--------------------------------------------------------------------*/
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#include "deSpinBarrier.hpp"
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#include "deThread.hpp"
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#include "deRandom.hpp"
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#include "deInt32.h"
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#include <vector>
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namespace de
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{
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SpinBarrier::SpinBarrier (deInt32 numThreads)
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: m_numCores (deGetNumAvailableLogicalCores())
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, m_numThreads (numThreads)
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, m_numEntered (0)
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, m_numLeaving (0)
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, m_numRemoved (0)
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{
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DE_ASSERT(numThreads > 0);
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}
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SpinBarrier::~SpinBarrier (void)
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{
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DE_ASSERT(m_numEntered == 0 && m_numLeaving == 0);
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}
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void SpinBarrier::reset (deUint32 numThreads)
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{
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// If last threads were removed, m_numEntered > 0 && m_numRemoved > 0
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DE_ASSERT(m_numLeaving == 0);
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DE_ASSERT(numThreads > 0);
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m_numThreads = numThreads;
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m_numEntered = 0;
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m_numLeaving = 0;
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m_numRemoved = 0;
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}
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inline SpinBarrier::WaitMode getWaitMode (SpinBarrier::WaitMode requested, deUint32 numCores, deInt32 numThreads)
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{
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if (requested == SpinBarrier::WAIT_MODE_AUTO)
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return ((deUint32)numThreads <= numCores) ? SpinBarrier::WAIT_MODE_BUSY : SpinBarrier::WAIT_MODE_YIELD;
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else
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return requested;
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}
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inline void wait (SpinBarrier::WaitMode mode)
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{
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DE_ASSERT(mode == SpinBarrier::WAIT_MODE_YIELD || mode == SpinBarrier::WAIT_MODE_BUSY);
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if (mode == SpinBarrier::WAIT_MODE_YIELD)
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deYield();
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}
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void SpinBarrier::sync (WaitMode requestedMode)
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{
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const deInt32 cachedNumThreads = m_numThreads;
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const WaitMode waitMode = getWaitMode(requestedMode, m_numCores, cachedNumThreads);
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deMemoryReadWriteFence();
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// m_numEntered must not be touched until all threads have had
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// a chance to observe it being 0.
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if (m_numLeaving > 0)
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{
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for (;;)
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{
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if (m_numLeaving == 0)
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break;
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wait(waitMode);
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}
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}
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// If m_numRemoved > 0, m_numThreads will decrease. If m_numThreads is decreased
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// just after atomicOp and before comparison, the branch could be taken by multiple
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// threads. Since m_numThreads only changes if all threads are inside the spinbarrier,
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// cached value at snapshotted at the beginning of the function will be equal for
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// all threads.
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if (deAtomicIncrement32(&m_numEntered) == cachedNumThreads)
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{
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// Release all waiting threads. Since this thread has not been removed, m_numLeaving will
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// be >= 1 until m_numLeaving is decremented at the end of this function.
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m_numThreads = m_numThreads - m_numRemoved;
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m_numLeaving = m_numThreads;
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m_numRemoved = 0;
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deMemoryReadWriteFence();
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m_numEntered = 0;
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}
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else
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{
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for (;;)
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{
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if (m_numEntered == 0)
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break;
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wait(waitMode);
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}
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}
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deAtomicDecrement32(&m_numLeaving);
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deMemoryReadWriteFence();
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}
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void SpinBarrier::removeThread (WaitMode requestedMode)
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{
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const deInt32 cachedNumThreads = m_numThreads;
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const WaitMode waitMode = getWaitMode(requestedMode, m_numCores, cachedNumThreads);
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// Wait for other threads exiting previous barrier
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if (m_numLeaving > 0)
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{
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for (;;)
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{
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if (m_numLeaving == 0)
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break;
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wait(waitMode);
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}
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}
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// Ask for last thread entering barrier to adjust thread count
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deAtomicIncrement32(&m_numRemoved);
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// See sync() - use cached value
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if (deAtomicIncrement32(&m_numEntered) == cachedNumThreads)
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{
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// Release all waiting threads.
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m_numThreads = m_numThreads - m_numRemoved;
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m_numLeaving = m_numThreads;
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m_numRemoved = 0;
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deMemoryReadWriteFence();
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m_numEntered = 0;
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}
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}
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namespace
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{
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void singleThreadTest (SpinBarrier::WaitMode mode)
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{
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SpinBarrier barrier(1);
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barrier.sync(mode);
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barrier.sync(mode);
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barrier.sync(mode);
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}
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class TestThread : public de::Thread
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{
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public:
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TestThread (SpinBarrier& barrier, volatile deInt32* sharedVar, int numThreads, int threadNdx)
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: m_barrier (barrier)
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, m_sharedVar (sharedVar)
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, m_numThreads (numThreads)
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, m_threadNdx (threadNdx)
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, m_busyOk ((deUint32)m_numThreads <= deGetNumAvailableLogicalCores())
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{
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}
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void run (void)
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{
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const int numIters = 10000;
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de::Random rnd (deInt32Hash(m_numThreads) ^ deInt32Hash(m_threadNdx));
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for (int iterNdx = 0; iterNdx < numIters; iterNdx++)
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{
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// Phase 1: count up
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deAtomicIncrement32(m_sharedVar);
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// Verify
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m_barrier.sync(getWaitMode(rnd));
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DE_TEST_ASSERT(*m_sharedVar == m_numThreads);
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m_barrier.sync(getWaitMode(rnd));
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// Phase 2: count down
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deAtomicDecrement32(m_sharedVar);
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// Verify
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m_barrier.sync(getWaitMode(rnd));
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DE_TEST_ASSERT(*m_sharedVar == 0);
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m_barrier.sync(getWaitMode(rnd));
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}
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}
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private:
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SpinBarrier& m_barrier;
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volatile deInt32* const m_sharedVar;
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const int m_numThreads;
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const int m_threadNdx;
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const bool m_busyOk;
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SpinBarrier::WaitMode getWaitMode (de::Random& rnd)
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{
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static const SpinBarrier::WaitMode s_allModes[] =
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{
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SpinBarrier::WAIT_MODE_YIELD,
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SpinBarrier::WAIT_MODE_AUTO,
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SpinBarrier::WAIT_MODE_BUSY,
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};
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const int numModes = DE_LENGTH_OF_ARRAY(s_allModes) - (m_busyOk ? 0 : 1);
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return rnd.choose<SpinBarrier::WaitMode>(DE_ARRAY_BEGIN(s_allModes), DE_ARRAY_BEGIN(s_allModes) + numModes);
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}
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};
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void multiThreadTest (int numThreads)
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{
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SpinBarrier barrier (numThreads);
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volatile deInt32 sharedVar = 0;
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std::vector<TestThread*> threads (numThreads, static_cast<TestThread*>(DE_NULL));
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for (int ndx = 0; ndx < numThreads; ndx++)
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{
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threads[ndx] = new TestThread(barrier, &sharedVar, numThreads, ndx);
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DE_TEST_ASSERT(threads[ndx]);
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threads[ndx]->start();
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}
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for (int ndx = 0; ndx < numThreads; ndx++)
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{
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threads[ndx]->join();
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delete threads[ndx];
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}
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DE_TEST_ASSERT(sharedVar == 0);
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}
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void singleThreadRemoveTest (SpinBarrier::WaitMode mode)
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{
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SpinBarrier barrier(3);
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barrier.removeThread(mode);
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barrier.removeThread(mode);
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barrier.sync(mode);
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barrier.removeThread(mode);
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barrier.reset(1);
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barrier.sync(mode);
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barrier.reset(2);
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barrier.removeThread(mode);
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barrier.sync(mode);
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}
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class TestExitThread : public de::Thread
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{
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public:
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TestExitThread (SpinBarrier& barrier, int numThreads, int threadNdx, SpinBarrier::WaitMode waitMode)
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: m_barrier (barrier)
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, m_numThreads (numThreads)
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, m_threadNdx (threadNdx)
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, m_waitMode (waitMode)
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{
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}
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void run (void)
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{
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const int numIters = 10000;
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de::Random rnd (deInt32Hash(m_numThreads) ^ deInt32Hash(m_threadNdx) ^ deInt32Hash((deInt32)m_waitMode));
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const int invExitProb = 1000;
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for (int iterNdx = 0; iterNdx < numIters; iterNdx++)
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{
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if (rnd.getInt(0, invExitProb) == 0)
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{
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m_barrier.removeThread(m_waitMode);
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break;
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}
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else
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m_barrier.sync(m_waitMode);
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}
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}
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private:
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SpinBarrier& m_barrier;
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const int m_numThreads;
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const int m_threadNdx;
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const SpinBarrier::WaitMode m_waitMode;
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};
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void multiThreadRemoveTest (int numThreads, SpinBarrier::WaitMode waitMode)
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{
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SpinBarrier barrier (numThreads);
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std::vector<TestExitThread*> threads (numThreads, static_cast<TestExitThread*>(DE_NULL));
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for (int ndx = 0; ndx < numThreads; ndx++)
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{
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threads[ndx] = new TestExitThread(barrier, numThreads, ndx, waitMode);
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DE_TEST_ASSERT(threads[ndx]);
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threads[ndx]->start();
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}
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for (int ndx = 0; ndx < numThreads; ndx++)
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{
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threads[ndx]->join();
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delete threads[ndx];
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}
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}
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} // anonymous
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void SpinBarrier_selfTest (void)
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{
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singleThreadTest(SpinBarrier::WAIT_MODE_YIELD);
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singleThreadTest(SpinBarrier::WAIT_MODE_BUSY);
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singleThreadTest(SpinBarrier::WAIT_MODE_AUTO);
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multiThreadTest(1);
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multiThreadTest(2);
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multiThreadTest(4);
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multiThreadTest(8);
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multiThreadTest(16);
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singleThreadRemoveTest(SpinBarrier::WAIT_MODE_YIELD);
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singleThreadRemoveTest(SpinBarrier::WAIT_MODE_BUSY);
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singleThreadRemoveTest(SpinBarrier::WAIT_MODE_AUTO);
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multiThreadRemoveTest(1, SpinBarrier::WAIT_MODE_BUSY);
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multiThreadRemoveTest(2, SpinBarrier::WAIT_MODE_AUTO);
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multiThreadRemoveTest(4, SpinBarrier::WAIT_MODE_AUTO);
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multiThreadRemoveTest(8, SpinBarrier::WAIT_MODE_AUTO);
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multiThreadRemoveTest(16, SpinBarrier::WAIT_MODE_AUTO);
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multiThreadRemoveTest(1, SpinBarrier::WAIT_MODE_YIELD);
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multiThreadRemoveTest(2, SpinBarrier::WAIT_MODE_YIELD);
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multiThreadRemoveTest(4, SpinBarrier::WAIT_MODE_YIELD);
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multiThreadRemoveTest(8, SpinBarrier::WAIT_MODE_YIELD);
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multiThreadRemoveTest(16, SpinBarrier::WAIT_MODE_YIELD);
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}
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} // de
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