MODIFIED JKQTPDataCache to implement a limited-size cache with least-…

…recently-used delete stategy
jkriege2 · Jan 24, 2024 · 1bf6c43 · 1bf6c43
1 parent 868d6dc
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diff --git a/examples/multithreaded/README.md b/examples/multithreaded/README.md
@@ -97,10 +97,10 @@ This test results in the following numbers (on my AMD Ryzen5 8/16-core laptop):
 <b>VERSION:</b> 5.0.0
 <b>BUILD MODE:</b> Release
 
-<u><b>SERIAL RESULTS:</b></u><br/>runtime, overall = 2336.7ms<br/>single runtimes = (97.3 +/- 158.4) ms<br/>speedup = 1.00x<br/>threads / available = 1 / 16<br/><br/><br/>  
+<u><b>SERIAL RESULTS:</b></u><br/>runtime, overall = 4241.3ms<br/>single runtimes = (176.7 +/- 319.6) ms<br/>speedup = 1.00x<br/>threads / available = 1 / 16<br/><br/><br/>  
 
 <u><b>PARALLEL RESULTS:</b></u><br/>
-runtime, overall = 527.2ms<br/>single runtimes = (166.4 +/- 8.1) ms<br/>speedup = 7.58x<br/>threads / available = 8 / 16<br/>batch runs = 3<br/><br/><b>speedup vs. serial = 4.4x</b>
+runtime, overall = 1025.3ms<br/>single runtimes = (325.0 +/- 15.0) ms<br/>speedup = 7.61x<br/>threads / available = 8 / 16<br/>batch runs = 3<br/><br/><b>speedup vs. serial = 4.1x</b>
 
 [comment]:RESULTS_END
 

diff --git a/lib/jkqtcommon/jkqtpcachingtools.h b/lib/jkqtcommon/jkqtpcachingtools.h
@@ -25,10 +25,24 @@
 #define JKQTPCACHINGTOOLS_H
 
 #include "jkqtcommon/jkqtcommon_imexport.h"
+#include "jkqtcommon/jkqtpmathtools.h"
 #include <QReadWriteLock>
 #include <QReadLocker>
 #include <QWriteLocker>
 #include <functional>
+#include <chrono>
+#include <atomic>
+#include <algorithm>
+#include <unordered_map>
+
+/** \brief tag type to configure JKQTPDataCache for thread-safety
+ *  \ingroup jkqtptools_concurrency
+ */
+struct JKQTPDataCacheThreadSafe {};
+/** \brief tag type to configure JKQTPDataCache for non thread-safety
+ *  \ingroup jkqtptools_concurrency
+ */
+struct JKQTPDataCacheNotThreadSafe {};
 
 /** \brief this class can be used to implement a general cache for values
  *  \ingroup jkqtptools_concurrency
@@ -45,51 +59,132 @@
  *
  *  Internally the cache maps TKey to TData, but the signature of the get()-function and the generator functor actually uses TKeyInSignature,
  *  which may differ from TKey. The only limitation is that TKeyInSignature can be converted/assigned to a TKey
+ *
+ *  The cache has a maximmum size m_maxEntries.
+ *  When you try to add a new object, after which the size would grow beyond this, a fraction 1-m_retainFraction of elements are
+ *  deleted from the cache. The delete strategy is least-recently used (LRU). In order to immplement this, the cache keeps track of
+ *  the last use timestamp of each entry.
+ *
+ *  You can deactivate the cleaning by setting m_maxEntries<0, but the the cache may grow indefinitely and there is possibly undefined behaviour
+ *  when add one too many items!
  */
-template <class TData, class TKey, bool ThreadSafe=true, class TKeyInSignature=TKey>
+template <class TData, class TKey, typename ThreadSafe=JKQTPDataCacheThreadSafe, class TKeyInSignature=TKey>
 struct JKQTPDataCache {
     template <typename FF>
-    inline JKQTPDataCache(FF generateData):
-        m_generateData(std::forward<FF>(generateData))
+    inline JKQTPDataCache(FF generateData, int maxEntries=10000, double retainFraction=0.8):
+        m_maxEntries(maxEntries), m_retainFraction(retainFraction), m_generateData(std::forward<FF>(generateData))
     {
 
     }
+    JKQTPDataCache()=delete;
+    JKQTPDataCache(const JKQTPDataCache&)=delete;
+    JKQTPDataCache& operator=(const JKQTPDataCache&)=delete;
+    JKQTPDataCache(JKQTPDataCache&&)=default;
+    JKQTPDataCache& operator=(JKQTPDataCache&&)=default;
 
     template<class... Args>
     inline TData get_inline(Args... args) {
         return get(TKeyInSignature(args...));
     }
 
-    template <bool TSS=ThreadSafe>
-    inline TData get(const typename std::enable_if<TSS, TKeyInSignature>::type& key) {
+    template <typename TSS=ThreadSafe>
+    inline TData get(const typename std::enable_if<std::is_same<JKQTPDataCacheThreadSafe, TSS>::value, TKeyInSignature>::type& key) {
         const TKey cacheKey=key;
 
         QReadLocker lockR(&m_mutex);
-        if (m_cache.contains(cacheKey)) return m_cache[cacheKey];
+        auto it=m_cache.find(cacheKey);
+        if (m_cache.end()!=it) {
+            m_cacheLastUseTimestamps[cacheKey]->exchange(currenTimestamp());
+            return it->second;
+        }
         lockR.unlock();
 
         QWriteLocker lockW(&m_mutex);
-        if (m_cache.contains(cacheKey)) return m_cache[cacheKey];
-
+        it=m_cache.find(cacheKey);
+        if (m_cache.end()!=it) {
+            m_cacheLastUseTimestamps.at(cacheKey)->exchange(currenTimestamp());
+            return it->second;
+        }
+        if (m_maxEntries>0 && m_cache.size()>=static_cast<size_t>(m_maxEntries)) cleanCache_notThreadSafe();
+        m_cacheLastUseTimestamps.emplace(cacheKey, std::make_shared<std::atomic<int64_t>>(currenTimestamp()));
         const auto newData=m_generateData(key);
-        m_cache[cacheKey]=newData;
+        m_cache.emplace(cacheKey,newData);
         return newData;
     }
 
-    template <bool TSS=ThreadSafe>
-    inline TData get(const typename std::enable_if<!TSS, TKeyInSignature>::type& key) {
+    template <typename TSS=ThreadSafe>
+    inline TData get(const typename std::enable_if<std::is_same<JKQTPDataCacheNotThreadSafe, TSS>::value, TKeyInSignature>::type& key) {
         const TKey cacheKey=key;
 
-        if (m_cache.contains(cacheKey)) return m_cache[cacheKey];
+        auto it=m_cache.find(cacheKey);
+        if (m_cache.end()!=it) {
+            m_cacheLastUseTimestamps[cacheKey]->exchange(currenTimestamp());
+            return it->second;
+        }
+        if (m_maxEntries>0 && m_cache.size()>=static_cast<size_t>(m_maxEntries)) cleanCache_notThreadSafe();
         const auto newData=m_generateData(key);
-        m_cache[cacheKey]=newData;
+        m_cache.emplace(cacheKey,newData);
+        m_cacheLastUseTimestamps.emplace(cacheKey, std::make_shared<std::atomic<int64_t>>(currenTimestamp()));
         return newData;
     }
+
+    template <typename TSS=ThreadSafe>
+    inline bool contains(const typename std::enable_if<std::is_same<JKQTPDataCacheThreadSafe, TSS>::value, TKeyInSignature>::type& key) const {
+        const TKey cacheKey=key;
+
+        QReadLocker lockR(&m_mutex);
+        return m_cache.find(cacheKey)!=m_cache.end();
+    }
+
+    template <typename TSS=ThreadSafe>
+    inline bool contains(const typename std::enable_if<std::is_same<JKQTPDataCacheNotThreadSafe, TSS>::value, TKeyInSignature>::type& key) const {
+        const TKey cacheKey=key;
+        return m_cache.find(cacheKey)!=m_cache.end();
+    }
+
+
+    inline int size() const {
+        return size_impl<ThreadSafe>();
+    }
+
 private:
-    QHash<TKey, TData> m_cache;
-    mutable typename std::enable_if<ThreadSafe, QReadWriteLock>::type m_mutex;
+    template <typename TSS>
+    inline typename std::enable_if<std::is_same<JKQTPDataCacheThreadSafe, TSS>::value, int>::type size_impl() const {
+        QReadLocker lockR(&m_mutex);
+        return m_cache.size();
+    }
+
+    template <typename TSS>
+    inline typename std::enable_if<std::is_same<JKQTPDataCacheNotThreadSafe, TSS>::value, int>::type size_impl() const {
+        return m_cache.size();
+    }
+
+    /** \brief generate a timestamp */
+    static inline int64_t currenTimestamp() {
+        static auto firstTime=std::chrono::steady_clock::now();
+        return std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::steady_clock::now()-firstTime).count();
+    }
+    /** \brief clean the cache, so at m_retainFraction*m_maxEntries entries remain. */
+    inline void cleanCache_notThreadSafe() {
+        if (m_maxEntries<0 || m_cache.size()<static_cast<size_t>(m_maxEntries)) return;
+        const int deleteItems=jkqtp_boundedRoundTo<int>(1, (1.0-m_retainFraction)*static_cast<double>(m_cache.size()), m_cache.size());
+        QList<QPair<TKey,int64_t> > allItems;
+        allItems.reserve(m_cacheLastUseTimestamps.size());
+        for (auto it=m_cacheLastUseTimestamps.begin(); it!=m_cacheLastUseTimestamps.end(); ++it) {
+            allItems.emplaceBack(it->first, it->second->load());
+        }
+        std::sort(allItems.begin(), allItems.end(), [](const QPair<TKey,int64_t>&a, const QPair<TKey,int64_t>&b) {return a.second>b.second;});
+        for (int i=0; i<deleteItems; i++) {
+            m_cache.erase(allItems[i].first);
+            m_cacheLastUseTimestamps.erase(allItems[i].first);
+        }
+    }
+    const int m_maxEntries;
+    const double m_retainFraction;
+    std::unordered_map<TKey, TData> m_cache;
+    std::unordered_map<TKey, std::shared_ptr<std::atomic<int64_t>>> m_cacheLastUseTimestamps;
+    mutable QReadWriteLock m_mutex;
     const std::function<TData(TKeyInSignature)> m_generateData;
-    Q_DISABLE_COPY(JKQTPDataCache)
 };
 
 #endif // JKQTPCACHINGTOOLS_H
diff --git a/lib/jkqtmathtext/jkqtmathtexttools.cpp b/lib/jkqtmathtext/jkqtmathtexttools.cpp
@@ -32,6 +32,7 @@
 #include <QFont>
 #include <QReadWriteLock>
 #include <mutex>
+#include <functional>
 
 
 void initJKQTMathTextResources()
@@ -884,6 +885,9 @@ QPainterPath JKQTMathTextMakeHBracePath(double x, double ybrace, double width, d
 namespace {
 
     struct JKQTMathTextCacheKeyBase {
+        JKQTMathTextCacheKeyBase():
+            f(), ldpiX(0), ldpiY(0), pdpiX(0), pdpiY(0)
+        {}
         inline explicit JKQTMathTextCacheKeyBase(const QFont& f_, QPaintDevice *pd):
             f(f_)
         {
@@ -904,7 +908,12 @@ namespace {
 
         inline bool operator==(const JKQTMathTextCacheKeyBase& other) const{
             return ldpiX==other.ldpiX &&  ldpiY==other.ldpiY && pdpiX==other.pdpiX &&  pdpiY==other.pdpiY && f==other.f;
-
+        };
+        inline bool operator<(const JKQTMathTextCacheKeyBase& other) const{
+            return ldpiX<other.ldpiX &&  ldpiY<other.ldpiY && pdpiX<other.pdpiX &&  pdpiY<other.pdpiY && f<other.f;
+        };
+        inline bool operator!=(const JKQTMathTextCacheKeyBase& other) const{
+            return !operator==(other);
         };
     };
 
@@ -931,6 +940,9 @@ namespace {
 
     template <class TText=QString>
     struct JKQTMathTextTBRDataH: public JKQTMathTextCacheKeyBase {
+        JKQTMathTextTBRDataH():
+            JKQTMathTextCacheKeyBase(), text("")
+        {}
         inline explicit JKQTMathTextTBRDataH(const QFont& f_, const TText& text_, QPaintDevice *pd):
             JKQTMathTextCacheKeyBase(f_, pd), text(text_)
         {
@@ -940,7 +952,12 @@ namespace {
 
         inline bool operator==(const JKQTMathTextTBRDataH& other) const{
             return JKQTMathTextCacheKeyBase::operator==(other) && text==other.text;
-
+        };
+        inline bool operator!=(const JKQTMathTextTBRDataH& other) const{
+            return JKQTMathTextCacheKeyBase::operator!=(other) && text!=other.text;
+        };
+        inline bool operator<(const JKQTMathTextTBRDataH& other) const{
+            return JKQTMathTextCacheKeyBase::operator<(other) && text<other.text;
         };
     };
 
@@ -967,13 +984,41 @@ namespace {
 
 }
 
+template<>
+struct std::hash<JKQTMathTextCacheKeyBase>
+{
+    std::size_t operator()(const JKQTMathTextCacheKeyBase& data) const noexcept
+    {
+        return qHash(data.f)+std::hash<int>()(data.ldpiX)+std::hash<int>()(data.ldpiY)+std::hash<int>()(data.pdpiX)+std::hash<int>()(data.pdpiY);
+    }
+};
+
+
+
+template<>
+struct std::hash<JKQTMathTextTBRDataH<QString>>
+{
+    std::size_t operator()(const JKQTMathTextTBRDataH<QString>& data) const noexcept
+    {
+        return qHash(data.f)+qHash(data.text)+std::hash<int>()(data.ldpiX)+std::hash<int>()(data.ldpiY)+std::hash<int>()(data.pdpiX)+std::hash<int>()(data.pdpiY);
+    }
+};
+
+template<>
+struct std::hash<JKQTMathTextTBRDataH<QChar>>
+{
+    std::size_t operator()(const JKQTMathTextTBRDataH<QChar>& data) const noexcept
+    {
+        return qHash(data.f)+qHash(data.text)+std::hash<int>()(data.ldpiX)+std::hash<int>()(data.ldpiY)+std::hash<int>()(data.pdpiX)+std::hash<int>()(data.pdpiY);
+    }
+};
 
 
 
 QRectF JKQTMathTextGetTightBoundingRect(const QFont &f, const QString &text, QPaintDevice *pd)
 {
     //thread_local JKQTPDataCache<QRectF,JKQTMathTextTBRDataH,false,JKQTMathTextTBRDataHExt> cache(
-    static JKQTPDataCache<QRectF,JKQTMathTextTBRDataH<QString>,true,JKQTMathTextTBRDataHExt<QString>> cache(
+    static JKQTPDataCache<QRectF,JKQTMathTextTBRDataH<QString>,JKQTPDataCacheThreadSafe,JKQTMathTextTBRDataHExt<QString>> cache(
                     [](const JKQTMathTextTBRDataHExt<QString>& key) {
                         const QFontMetricsF fm(key.f, key.pd);
                         return fm.tightBoundingRect(key.text);
@@ -986,7 +1031,7 @@ QRectF JKQTMathTextGetTightBoundingRect(const QFont &f, const QString &text, QPa
 QRectF JKQTMathTextGetBoundingRect(const QFont &f, const QString &text, QPaintDevice *pd)
 {
     //thread_local JKQTPDataCache<QRectF,JKQTMathTextTBRDataH,false,JKQTMathTextTBRDataHExt> cache(
-    static JKQTPDataCache<QRectF,JKQTMathTextTBRDataH<QString>,true,JKQTMathTextTBRDataHExt<QString>> cache(
+    static JKQTPDataCache<QRectF,JKQTMathTextTBRDataH<QString>,JKQTPDataCacheThreadSafe,JKQTMathTextTBRDataHExt<QString>> cache(
         [](const JKQTMathTextTBRDataHExt<QString>& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.boundingRect(key.text);
@@ -999,7 +1044,7 @@ QRectF JKQTMathTextGetBoundingRect(const QFont &f, const QString &text, QPaintDe
 qreal JKQTMathTextGetHorAdvance(const QFont &f, const QString &text, QPaintDevice *pd)
 {
     //thread_local JKQTPDataCache<double,JKQTMathTextTBRDataH,false,JKQTMathTextTBRDataHExt> cache(
-    static JKQTPDataCache<qreal,JKQTMathTextTBRDataH<QString>,true,JKQTMathTextTBRDataHExt<QString>> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextTBRDataH<QString>,JKQTPDataCacheThreadSafe,JKQTMathTextTBRDataHExt<QString>> cache(
         [](const JKQTMathTextTBRDataHExt<QString>& key) {
             const QFontMetricsF fm(key.f, key.pd);
 #if (QT_VERSION>=QT_VERSION_CHECK(5, 15, 0))
@@ -1016,7 +1061,7 @@ qreal JKQTMathTextGetHorAdvance(const QFont &f, const QString &text, QPaintDevic
 qreal JKQTMathTextGetRightBearing(const QFont &f, const QChar &text, QPaintDevice *pd)
 {
     //thread_local JKQTPDataCache<double,JKQTMathTextTBRDataH,false,JKQTMathTextTBRDataHExt> cache(
-    static JKQTPDataCache<qreal,JKQTMathTextTBRDataH<QChar>,true,JKQTMathTextTBRDataHExt<QChar>> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextTBRDataH<QChar>,JKQTPDataCacheThreadSafe,JKQTMathTextTBRDataHExt<QChar>> cache(
         [](const JKQTMathTextTBRDataHExt<QChar>& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.rightBearing(key.text);
@@ -1028,7 +1073,7 @@ qreal JKQTMathTextGetRightBearing(const QFont &f, const QChar &text, QPaintDevic
 qreal JKQTMathTextGetLeftBearing(const QFont &f, const QChar &text, QPaintDevice *pd)
 {
     //thread_local JKQTPDataCache<double,JKQTMathTextTBRDataH,false,JKQTMathTextTBRDataHExt> cache(
-    static JKQTPDataCache<qreal,JKQTMathTextTBRDataH<QChar>,true,JKQTMathTextTBRDataHExt<QChar>> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextTBRDataH<QChar>,JKQTPDataCacheThreadSafe,JKQTMathTextTBRDataHExt<QChar>> cache(
         [](const JKQTMathTextTBRDataHExt<QChar>& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.leftBearing(key.text);
@@ -1040,7 +1085,7 @@ qreal JKQTMathTextGetLeftBearing(const QFont &f, const QChar &text, QPaintDevice
 
 qreal JKQTMathTextGetFontAscent(const QFont &f, QPaintDevice *pd)
 {
-    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,true,JKQTMathTextCacheKeyBaseExt> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,JKQTPDataCacheThreadSafe,JKQTMathTextCacheKeyBaseExt> cache(
         [](const JKQTMathTextCacheKeyBaseExt& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.ascent();
@@ -1051,7 +1096,7 @@ qreal JKQTMathTextGetFontAscent(const QFont &f, QPaintDevice *pd)
 
 qreal JKQTMathTextGetFontDescent(const QFont &f, QPaintDevice *pd)
 {
-    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,true,JKQTMathTextCacheKeyBaseExt> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,JKQTPDataCacheThreadSafe,JKQTMathTextCacheKeyBaseExt> cache(
         [](const JKQTMathTextCacheKeyBaseExt& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.descent();
@@ -1062,7 +1107,7 @@ qreal JKQTMathTextGetFontDescent(const QFont &f, QPaintDevice *pd)
 
 qreal JKQTMathTextGetFontHeight(const QFont &f, QPaintDevice *pd)
 {
-    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,true,JKQTMathTextCacheKeyBaseExt> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,JKQTPDataCacheThreadSafe,JKQTMathTextCacheKeyBaseExt> cache(
         [](const JKQTMathTextCacheKeyBaseExt& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.height();
@@ -1073,7 +1118,7 @@ qreal JKQTMathTextGetFontHeight(const QFont &f, QPaintDevice *pd)
 
 qreal JKQTMathTextGetFontLineWidth(const QFont &f, QPaintDevice *pd)
 {
-    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,true,JKQTMathTextCacheKeyBaseExt> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,JKQTPDataCacheThreadSafe,JKQTMathTextCacheKeyBaseExt> cache(
         [](const JKQTMathTextCacheKeyBaseExt& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.lineWidth();
@@ -1084,7 +1129,7 @@ qreal JKQTMathTextGetFontLineWidth(const QFont &f, QPaintDevice *pd)
 
 qreal JKQTMathTextGetFontLeading(const QFont &f, QPaintDevice *pd)
 {
-    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,true,JKQTMathTextCacheKeyBaseExt> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,JKQTPDataCacheThreadSafe,JKQTMathTextCacheKeyBaseExt> cache(
         [](const JKQTMathTextCacheKeyBaseExt& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.leading();
@@ -1095,7 +1140,7 @@ qreal JKQTMathTextGetFontLeading(const QFont &f, QPaintDevice *pd)
 
 qreal JKQTMathTextGetFontLineSpacing(const QFont &f, QPaintDevice *pd)
 {
-    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,true,JKQTMathTextCacheKeyBaseExt> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,JKQTPDataCacheThreadSafe,JKQTMathTextCacheKeyBaseExt> cache(
         [](const JKQTMathTextCacheKeyBaseExt& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.lineSpacing();
@@ -1106,7 +1151,7 @@ qreal JKQTMathTextGetFontLineSpacing(const QFont &f, QPaintDevice *pd)
 
 qreal JKQTMathTextGetFontStrikoutPos(const QFont &f, QPaintDevice *pd)
 {
-    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,true,JKQTMathTextCacheKeyBaseExt> cache(
+    static JKQTPDataCache<qreal,JKQTMathTextCacheKeyBase,JKQTPDataCacheThreadSafe,JKQTMathTextCacheKeyBaseExt> cache(
         [](const JKQTMathTextCacheKeyBaseExt& key) {
             const QFontMetricsF fm(key.f, key.pd);
             return fm.strikeOutPos();

diff --git a/screenshots/multithreaded.png b/screenshots/multithreaded.png
diff --git a/screenshots/multithreaded_small.png b/screenshots/multithreaded_small.png