Adding upstream version 4:7.4.7.upstream/4%7.4.7upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 373 insertions, 0 deletions

diff --git a/include/comphelper/parallelsort.hxx b/include/comphelper/parallelsort.hxx
new file mode 100644
index 000000000..94d86e0d1
--- /dev/null
+++ b/include/comphelper/parallelsort.hxx
@@ -0,0 +1,373 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef INCLUDED_COMPHELPER_PARALLELSORT_HXX
+#define INCLUDED_COMPHELPER_PARALLELSORT_HXX
+
+#include <comphelper/threadpool.hxx>
+#include <tools/cpuid.hxx>
+
+#include <memory>
+#include <iterator>
+#include <thread>
+#include <algorithm>
+#include <cmath>
+#include <random>
+#include <functional>
+#include <iostream>
+#include <chrono>
+
+namespace comphelper
+{
+const size_t nThreadCountGlobal = std::thread::hardware_concurrency();
+const bool bHyperThreadingActive = cpuid::hasHyperThreading();
+static comphelper::ThreadPool& rTPool(comphelper::ThreadPool::getSharedOptimalPool());
+
+static thread_local std::mt19937 aGenerator{ std::random_device{}() };
+
+#define PARALLELSORT_ENABLEPZ 0
+
+namespace
+{
+class ProfileZone
+{
+public:
+#if PARALLELSORT_ENABLEPZ
+    ProfileZone(const char* pTag)
+        : maTag(pTag)
+        , maStart(std::chrono::steady_clock::now())
+        , mbFinished(false)
+    {
+    }
+
+    ~ProfileZone()
+    {
+        if (!mbFinished)
+            showTimeElapsed();
+    }
+
+    void stop()
+    {
+        showTimeElapsed();
+        mbFinished = true;
+    }
+#else
+    ProfileZone(const char* /*pTag*/)
+        : mbDummy(true)
+    {
+    }
+
+    void stop()
+    {
+        // Avoid loplugin:staticmethods, loplugin:staticaccess errors
+        (void)mbDummy;
+    }
+#endif
+
+private:
+#if PARALLELSORT_ENABLEPZ
+
+    void showTimeElapsed()
+    {
+        auto end = std::chrono::steady_clock::now();
+        size_t elapsed
+            = std::chrono::duration_cast<std::chrono::milliseconds>(end - maStart).count();
+        std::cout << maTag << " : " << elapsed << " ms" << std::endl << std::flush;
+    }
+
+    std::string maTag;
+    std::chrono::steady_clock::time_point maStart;
+    bool mbFinished;
+#else
+    bool mbDummy;
+
+#endif
+};
+
+class ParallelRunner
+{
+    class Executor final : public comphelper::ThreadTask
+    {
+    public:
+        Executor(const std::shared_ptr<comphelper::ThreadTaskTag>& rTag,
+                 std::function<void()> aFunc)
+            : comphelper::ThreadTask(rTag)
+            , maFunc(std::move(aFunc))
+        {
+        }
+
+        virtual void doWork() override { maFunc(); }
+
+    private:
+        const std::function<void()> maFunc;
+    };
+
+public:
+    ParallelRunner() { maTag = comphelper::ThreadPool::createThreadTaskTag(); }
+
+    void enqueue(std::function<void()> aFunc)
+    {
+        rTPool.pushTask(std::make_unique<Executor>(maTag, aFunc));
+    }
+
+    void wait() { rTPool.waitUntilDone(maTag, false); }
+
+private:
+    std::shared_ptr<comphelper::ThreadTaskTag> maTag;
+};
+
+constexpr size_t nMaxTreeArraySize = 64;
+
+size_t lcl_round_down_pow2(size_t nNum)
+{
+    size_t nPow2;
+    for (nPow2 = 1; nPow2 <= nNum; nPow2 <<= 1)
+        ;
+    return std::min((nPow2 >> 1), nMaxTreeArraySize);
+}
+
+template <class RandItr> struct Sampler
+{
+    using ValueType = typename std::iterator_traits<RandItr>::value_type;
+
+    static void sample(RandItr aBegin, RandItr aEnd, ValueType* pSamples, size_t nSamples,
+                       size_t /*nParallelism*/)
+    {
+        ProfileZone aZone("\tsample()");
+        assert(aBegin <= aEnd);
+        size_t nLen = static_cast<std::size_t>(aEnd - aBegin);
+        assert(std::mt19937::max() >= nLen);
+
+        for (size_t nIdx = 0; nIdx < nSamples; ++nIdx)
+        {
+            size_t nSel = aGenerator() % nLen--;
+            using namespace std;
+            swap(*(aBegin + nSel), *(aBegin + nLen));
+            pSamples[nIdx] = *(aBegin + nLen);
+        }
+    }
+};
+
+template <class RandItr, class Compare> class Binner
+{
+    using ValueType = typename std::iterator_traits<RandItr>::value_type;
+
+    const size_t mnTreeArraySize;
+    const size_t mnDividers;
+    constexpr static size_t mnMaxStaticSize = 1024 * 50;
+    uint8_t maLabels[mnMaxStaticSize];
+    ValueType maDividers[nMaxTreeArraySize];
+    std::unique_ptr<uint8_t[]> pLabels;
+    size_t maSepBinEnds[nMaxTreeArraySize * nMaxTreeArraySize];
+    bool mbThreaded;
+
+public:
+    size_t maBinEnds[nMaxTreeArraySize];
+
+    Binner(const ValueType* pSamples, size_t nSamples, size_t nBins, bool bThreaded)
+        : mnTreeArraySize(lcl_round_down_pow2(nBins))
+        , mnDividers(mnTreeArraySize - 1)
+        , mbThreaded(bThreaded)
+    {
+        assert((nSamples % mnTreeArraySize) == 0);
+        assert(mnTreeArraySize <= nMaxTreeArraySize);
+        std::fill(maBinEnds, maBinEnds + mnTreeArraySize, 0);
+        std::fill(maSepBinEnds, maSepBinEnds + mnTreeArraySize * mnTreeArraySize, 0);
+        fillTreeArray(1, pSamples, pSamples + nSamples);
+    }
+
+    void fillTreeArray(size_t nPos, const ValueType* pLow, const ValueType* pHigh)
+    {
+        assert(pLow <= pHigh);
+        const ValueType* pMid = pLow + (pHigh - pLow) / 2;
+        maDividers[nPos] = *pMid;
+
+        if (2 * nPos < mnDividers) // So that 2*nPos < mnTreeArraySize
+        {
+            fillTreeArray(2 * nPos, pLow, pMid);
+            fillTreeArray(2 * nPos + 1, pMid + 1, pHigh);
+        }
+    }
+
+    constexpr inline size_t findBin(const ValueType& rVal, Compare& aComp)
+    {
+        size_t nIdx = 1;
+        while (nIdx <= mnDividers)
+            nIdx = ((nIdx << 1) + aComp(maDividers[nIdx], rVal));
+        return (nIdx - mnTreeArraySize);
+    }
+
+    void label(const RandItr aBegin, const RandItr aEnd, Compare& aComp)
+    {
+        ProfileZone aZoneSetup("\tlabel():setup");
+        size_t nLen = static_cast<std::size_t>(aEnd - aBegin);
+        if (nLen > mnMaxStaticSize)
+            pLabels = std::make_unique<uint8_t[]>(nLen);
+        uint8_t* pLabelsRaw = (nLen > mnMaxStaticSize) ? pLabels.get() : maLabels;
+        aZoneSetup.stop();
+        ProfileZone aZoneFindBins("\tFindBins()");
+        if (mbThreaded)
+        {
+            ParallelRunner aPRunner;
+            const size_t nBins = mnTreeArraySize;
+            for (size_t nTIdx = 0; nTIdx < nBins; ++nTIdx)
+            {
+                aPRunner.enqueue([this, nTIdx, nBins, nLen, aBegin, pLabelsRaw, &aComp] {
+                    ProfileZone aZoneIn("\t\tFindBinsThreaded()");
+                    size_t nBinEndsStartIdx = nTIdx * mnTreeArraySize;
+                    size_t* pBinEnds = maSepBinEnds + nBinEndsStartIdx;
+                    size_t aBinEndsF[nMaxTreeArraySize] = { 0 };
+                    for (size_t nIdx = nTIdx; nIdx < nLen; nIdx += nBins)
+                    {
+                        size_t nBinIdx = findBin(*(aBegin + nIdx), aComp);
+                        pLabelsRaw[nIdx] = static_cast<uint8_t>(nBinIdx);
+                        ++aBinEndsF[nBinIdx];
+                    }
+
+                    for (size_t nIdx = 0; nIdx < mnTreeArraySize; ++nIdx)
+                        pBinEnds[nIdx] = aBinEndsF[nIdx];
+                });
+            }
+
+            aPRunner.wait();
+
+            // Populate maBinEnds from maSepBinEnds
+            for (size_t nTIdx = 0; nTIdx < mnTreeArraySize; ++nTIdx)
+            {
+                for (size_t nSepIdx = 0; nSepIdx < mnTreeArraySize; ++nSepIdx)
+                    maBinEnds[nTIdx] += maSepBinEnds[nSepIdx * mnTreeArraySize + nTIdx];
+            }
+        }
+        else
+        {
+            uint8_t* pLabel = pLabelsRaw;
+            for (RandItr aItr = aBegin; aItr != aEnd; ++aItr)
+            {
+                size_t nBinIdx = findBin(*aItr, aComp);
+                *pLabel++ = nBinIdx;
+                ++maBinEnds[nBinIdx];
+            }
+        }
+
+        aZoneFindBins.stop();
+
+        size_t nSum = 0;
+        // Store each bin's starting position in maBinEnds array for now.
+        for (size_t nIdx = 0; nIdx < mnTreeArraySize; ++nIdx)
+        {
+            size_t nSize = maBinEnds[nIdx];
+            maBinEnds[nIdx] = nSum;
+            nSum += nSize;
+        }
+
+        // Now maBinEnds has end positions of each bin.
+    }
+
+    void bin(const RandItr aBegin, const RandItr aEnd, ValueType* pOut)
+    {
+        ProfileZone aZone("\tbin()");
+        const size_t nLen = static_cast<std::size_t>(aEnd - aBegin);
+        uint8_t* pLabelsRaw = (nLen > mnMaxStaticSize) ? pLabels.get() : maLabels;
+        size_t nIdx;
+        for (nIdx = 0; nIdx < nLen; ++nIdx)
+        {
+            pOut[maBinEnds[pLabelsRaw[nIdx]]++] = *(aBegin + nIdx);
+        }
+    }
+};
+
+template <class RandItr, class Compare = std::less<>>
+void s3sort(const RandItr aBegin, const RandItr aEnd, Compare aComp = Compare(),
+            bool bThreaded = true)
+{
+    static size_t nThreadCount = nThreadCountGlobal;
+
+    constexpr size_t nBaseCaseSize = 1024;
+    const std::size_t nLen = static_cast<std::size_t>(aEnd - aBegin);
+    if (nLen < nBaseCaseSize)
+    {
+        std::sort(aBegin, aEnd, aComp);
+        return;
+    }
+
+    using ValueType = typename std::iterator_traits<RandItr>::value_type;
+    auto pOut = std::make_unique<ValueType[]>(nLen);
+
+    const size_t nBins = lcl_round_down_pow2(nThreadCount);
+    const size_t nOverSamplingFactor = std::max(1.0, std::sqrt(static_cast<double>(nLen) / 64));
+    const size_t nSamples = nOverSamplingFactor * nBins;
+    auto aSamples = std::make_unique<ValueType[]>(nSamples);
+    ProfileZone aZoneSampleAnsSort("SampleAndSort");
+    // Select samples and sort them
+    Sampler<RandItr>::sample(aBegin, aEnd, aSamples.get(), nSamples, nBins);
+    std::sort(aSamples.get(), aSamples.get() + nSamples, aComp);
+    aZoneSampleAnsSort.stop();
+
+    if (!aComp(aSamples[0], aSamples[nSamples - 1]))
+    {
+        // All samples are equal, fallback to standard sort.
+        std::sort(aBegin, aEnd, aComp);
+        return;
+    }
+
+    ProfileZone aZoneBinner("Binner");
+    // Create and populate bins using pOut from input iterators.
+    Binner<RandItr, Compare> aBinner(aSamples.get(), nSamples, nBins, bThreaded);
+    aBinner.label(aBegin, aEnd, aComp);
+    aBinner.bin(aBegin, aEnd, pOut.get());
+    aZoneBinner.stop();
+
+    ProfileZone aZoneSortBins("SortBins");
+    ValueType* pOutRaw = pOut.get();
+    if (bThreaded)
+    {
+        ParallelRunner aPRunner;
+        // Sort the bins separately.
+        for (size_t nBinIdx = 0, nBinStart = 0; nBinIdx < nBins; ++nBinIdx)
+        {
+            size_t nBinEnd = aBinner.maBinEnds[nBinIdx];
+            aPRunner.enqueue([pOutRaw, nBinStart, nBinEnd, &aComp] {
+                std::sort(pOutRaw + nBinStart, pOutRaw + nBinEnd, aComp);
+            });
+
+            nBinStart = nBinEnd;
+        }
+
+        aPRunner.wait();
+    }
+    else
+    {
+        for (size_t nBinIdx = 0, nBinStart = 0; nBinIdx < nBins; ++nBinIdx)
+        {
+            auto nBinEnd = aBinner.maBinEnds[nBinIdx];
+            std::sort(pOutRaw + nBinStart, pOutRaw + nBinEnd, aComp);
+            nBinStart = nBinEnd;
+        }
+    }
+
+    aZoneSortBins.stop();
+
+    // Move the sorted array to the array specified by input iterators.
+    std::move(pOutRaw, pOutRaw + nLen, aBegin);
+}
+
+} // anonymous namespace
+
+template <class RandItr, class Compare = std::less<>>
+void parallelSort(const RandItr aBegin, const RandItr aEnd, Compare aComp = Compare())
+{
+    assert(aBegin <= aEnd);
+    s3sort(aBegin, aEnd, aComp);
+}
+
+} // namespace comphelper
+
+#endif // INCLUDED_COMPHELPER_PARALLELSORT_HXX
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */