task2/include/quicksort_mt.h

@@ -19,24 +19,28 @@ public:
 
 private:
     auto parition(std::span<T> &data) -> std::pair<std::span<T>, std::span<T>> {
-        auto pivot = data.begin();
-        std::advance(pivot, std::distance(data.begin(), data.end()) / 2);
 
-        auto lefti = data.begin();
-        auto righti = data.end() - 1;
+        std::vector<T> buf(data);
+
+        auto pivot = buf.begin();
+        std::advance(pivot, std::distance(buf.begin(), buf.end()) / 2);
+
+        auto lefti = buf.begin();
+        auto righti = buf.end();
 
         while (1) {
-            for (; cmp((*lefti), (*pivot)); lefti++);
-            for (; !cmp((*righti), (*pivot)); righti--);
+            for (; cmp(*lefti, *pivot); lefti++);
+            for (; !cmp(*righti, *pivot); righti--);
 
             if (lefti >= righti) {
                 break;
             }
 
-            std::swap(*lefti, *righti);
+            std::swap(lefti, righti);
         }
 
-        return {std::span<T>(data.begin(), pivot - 1), std::span<T>(pivot + 1, data.end())};
+        std::move(buf.begin(), buf.end(), data.begin());
+        return {std::span<T>(data.begin(), lefti), std::span<T>(lefti, data.end())};
     }
 
 
@@ -50,9 +54,13 @@ private:
             }
         }
 
-        auto res = parition(data);
-        auto &left = res.first;
-        auto &right = res.second;
+        // Determine mid of data
+        auto mid = data.begin();
+        std::advance(mid, std::distance(data.begin(), data.end()) / 2);
+
+        // Generate left and right view on data (no copies are made here)
+        std::span<T> left(data.begin(), mid);
+        std::span<T> right(mid, data.end());
 
         if (depth < mdepth) {
             std::thread left_thread([&]() { qsort(left, depth + 1, mdepth); });

task3/CMakeLists.txt

@@ -1,9 +1,10 @@
+
 find_package(Qt6 COMPONENTS Core REQUIRED)
 
-add_executable(task3-chpt3ex12-rd)
+add_executable(task3-chpt3ex12)
 
-target_sources(task3-chpt3ex12-rd PRIVATE
-        main-rd.cpp)
+target_sources(task3-chpt3ex12 PRIVATE
+        main.cpp)
 
-target_link_libraries(task3-chpt3ex12-rd PRIVATE
+target_link_libraries(task3-chpt3ex12 PRIVATE
         Qt6::Core)

task3/main-rd.cpp

@@ -1,109 +0,0 @@
-#include <iostream>
-#include <QSemaphore>
-#include <QThread>
-#include <QCoreApplication>
-
-/*
- * Barlas Chpt 3 Ex 12:
-    Create three threads, each printing out the letters A, B, and C.
-    The printing must adhere to these rules:
-        • The total number of Bs and Cs that have been output at any
-          point in the output string cannot exceed the total number
-          of As that have been output at that point.
-        • After a C has been output, another C cannot be output until
-          one or more Bs have been output.
-    Use semaphores to solve the problem.
-*/
-
-struct IPrintable {
-    ~IPrintable() = default;
-
-    virtual auto print() const -> void = 0;
-};
-
-class PrintA : public IPrintable {
-private:
-    QSemaphore &lockBC_;
-public:
-    explicit PrintA(QSemaphore &lockBc) : lockBC_(lockBc) {}
-
-    auto print() const -> void override {
-        this->lockBC_.release(1);
-        std::cout << "A";
-    }
-};
-
-class PrintB : public IPrintable {
-private:
-    QSemaphore &lockBC_;
-    QSemaphore &lockC_;
-public:
-    explicit PrintB(QSemaphore &lockBc, QSemaphore &lockC) : lockBC_(lockBc), lockC_(lockC) {}
-
-    auto print() const -> void override {
-        if (this->lockBC_.tryAcquire(1)) {
-            if (this->lockC_.available() == 0) {
-                this->lockC_.release(1);
-            }
-            std::cout << "B";
-        }
-    }
-};
-
-class PrintC : public IPrintable {
-private:
-    QSemaphore &lockBC_;
-    QSemaphore &lockC_;
-public:
-    explicit PrintC(QSemaphore &lockBc, QSemaphore &lockC) : lockBC_(lockBc), lockC_(lockC) {}
-
-    auto print() const -> void override {
-        if (this->lockBC_.tryAcquire(1)) {
-            if (this->lockC_.tryAcquire(1)) {
-                std::cout << "C";
-            } else {
-                this->lockBC_.release(1);
-            }
-        }
-    }
-};
-
-
-template<typename T, typename ...Argts>
-class Worker : public QThread {
-private:
-    std::unique_ptr<IPrintable> printer_;
-public:
-    Worker(QString tname, Argts &... args) : printer_(std::make_unique<T>(args...)) {};
-
-protected:
-    void run() {
-        while (true) {
-            printer_->print();
-            std::cout.flush();
-            sleep(1);
-        }
-    }
-};
-
-
-int main(int argc, char *argv[]) {
-    //QCoreApplication app(argc, argv);
-
-    QSemaphore lockC(1);
-    QSemaphore lockBC(0);
-
-    Worker<PrintA, QSemaphore> t1("Thread 1", lockBC);
-    Worker<PrintB, QSemaphore, QSemaphore> t2("Thread 1", lockBC, lockC);
-    Worker<PrintC, QSemaphore, QSemaphore> t3("Thread 1", lockBC, lockC);
-
-    t1.start();
-    t2.start();
-    t3.start();
-
-    t1.wait();
-    t2.wait();
-    t3.wait();
-    //return app.exec();
-    return 0;
-}

task3/main.cpp

@@ -0,0 +1,83 @@
+#include <iostream>
+#include <QSemaphore>
+#include <QThread>
+#include <QCoreApplication>
+
+/*
+ * Barlas Chpt 3 Ex 12:
+    Create three threads, each printing out the letters A, B, and C.
+    The printing must adhere to these rules:
+        • The total number of Bs and Cs that have been output at any
+          point in the output string cannot exceed the total number
+          of As that have been output at that point.
+        • After a C has been output, another C cannot be output until
+          one or more Bs have been output.
+    Use semaphores to solve the problem.
+*/
+
+class Printer {
+private:
+    QSemaphore &lockBC_;
+    QSemaphore &lockC_;
+
+    QString name_;
+
+public:
+    explicit Printer(QSemaphore &lockBC, QSemaphore &lockC, QString name) : lockBC_(lockBC), lockC_(lockC),
+                                                                            name_(name) {};
+
+    void printA() {
+        this->lockBC_.release(1);
+        std::cout << name_.toStdString() << " A\n";
+    }
+
+    void printB() {
+        if (this->lockBC_.tryAcquire(1, 10000)) {
+            if (this->lockC_.available() == 0) {
+                this->lockC_.release(1);
+            }
+            std::cout << name_.toStdString() << " B\n";
+        }
+    }
+
+    void printC() {
+        if (this->lockBC_.tryAcquire(1, 10000)) {
+            if (this->lockC_.tryAcquire(1, 10000)) {
+                std::cout << name_.toStdString() << " C\n";
+            } else {
+                this->lockBC_.release(1);
+            }
+        }
+    }
+};
+
+class Worker : public QThread {
+private:
+    Printer printer_;
+
+public:
+    Worker(QSemaphore &lockBC, QSemaphore &lockC, QString tname) : printer_(lockBC, lockC, tname) {};
+
+protected:
+    void run() {
+        printer_.printA();
+        printer_.printB();
+        printer_.printC();
+    }
+};
+
+
+int main(int argc, char *argv[]) {
+    QCoreApplication app(argc, argv);
+    QSemaphore lockC(1);
+    QSemaphore lockBC(0);
+
+    int N = 3;
+    Worker *workers[N];
+    for (int i = 0; i < N; i++) {
+        workers[i] = new Worker(lockBC, lockC, QString("Thread %1").arg(i));
+        workers[i]->start();
+    }
+
+    return app.exec();
+}