From 4b7bf34724fb1a8c0a135ae3127548e495c0ad2c Mon Sep 17 00:00:00 2001
From: Gems <12239620+gems-xu@user.noreply.gitee.com>
Date: Wed, 10 May 2023 00:31:48 +0000
Subject: [PATCH] Add concurrency program

Signed-off-by: Gems <12239620+gems-xu@user.noreply.gitee.com>
---
 basic_content/concurrency/README.md |  9 ++++
 basic_content/concurrency/main.cpp  | 51 ++++++++++++++++++++++
 basic_content/concurrency/sort.cpp  | 66 +++++++++++++++++++++++++++++
 3 files changed, 126 insertions(+)
 create mode 100644 basic_content/concurrency/README.md
 create mode 100644 basic_content/concurrency/main.cpp
 create mode 100644 basic_content/concurrency/sort.cpp

diff --git a/basic_content/concurrency/README.md b/basic_content/concurrency/README.md
new file mode 100644
index 0000000..ac3acc5
--- /dev/null
+++ b/basic_content/concurrency/README.md
@@ -0,0 +1,9 @@
+## C++ concurrency program
+
+1. Multithreaded sorting
+2. Thread-safe data structures
+    - Thread-safe queue
+    - Thread-safe stack
+    - ...
+3. Hierarchical mutex
+4. To be added...
\ No newline at end of file
diff --git a/basic_content/concurrency/main.cpp b/basic_content/concurrency/main.cpp
new file mode 100644
index 0000000..2d95b0d
--- /dev/null
+++ b/basic_content/concurrency/main.cpp
@@ -0,0 +1,51 @@
+#include <iostream>
+#include <future>
+#include <cassert>
+#include <random>
+#include <algorithm>
+#include "sort.cpp"
+
+double sqrt_root(double x){
+    if(x < 0){
+        throw std::out_of_range("x < 0");
+    }
+    return sqrt(x);
+}
+
+int main(){
+//    double y = sqrt_root(-1);
+    std::future<double> f = std::async(sqrt_root, -1);
+//    double y = f.get();
+
+    std::promise<int> p;
+    std::future f2(p.get_future());  // std::future<int>
+    assert(f2.valid());
+    std::shared_future sf(std::move(f2));
+    assert(!f2.valid());
+    assert(sf.valid());
+
+    /*** sort test ***/
+    std::default_random_engine e;
+    std::list<int> l, l2, l3;
+    for(int i = 0; i < 8e4; ++i){
+        l.emplace_back(e() % 10000);
+    }
+    l2 = l3 = l;
+    clock_t start = clock();
+    std::thread t(seq_q_sort<int>, std::move(l));
+    t.join();
+//    auto ans = seq_q_sort(std::move(l));
+    std::cout << clock() - start << std::endl;
+
+    start = clock();
+    auto ans2 = parallel_q_sort(std::move(l2));
+    std::cout << clock() - start << std::endl;
+
+    start = clock();
+    l3.sort([](const auto& num1, const auto& num2){
+        return num1 < num2;
+    });
+    std::cout << clock() - start << std::endl;
+
+    return 0;
+}
\ No newline at end of file
diff --git a/basic_content/concurrency/sort.cpp b/basic_content/concurrency/sort.cpp
new file mode 100644
index 0000000..9800609
--- /dev/null
+++ b/basic_content/concurrency/sort.cpp
@@ -0,0 +1,66 @@
+//
+// Created by gmes on 2022/5/30.
+//
+
+#include <list>
+
+template<typename T>
+std::list<T> seq_q_sort(std::list<T> input){
+    if(input.empty()){
+        return input;
+    }
+    std::list<T> ans;
+    ans.splice(ans.begin(), input, input.begin());
+    const T& pivot = *ans.begin();
+
+    auto divide_point = std::partition(input.begin(), input.end(), [&](const T& t){
+        return t < pivot;
+    });
+
+    std::list<T> lower_part;
+    lower_part.splice(lower_part.end(), input, input.begin(), divide_point);
+
+    auto new_lower(seq_q_sort(std::move(lower_part)));
+    auto new_higher(seq_q_sort(std::move(input)));
+
+    ans.splice(ans.end(), new_higher);
+    ans.splice(ans.begin(), new_lower);
+    return ans;
+}
+
+template<typename T>
+std::list<T> parallel_q_sort(std::list<T> input){
+    if(input.empty()){
+        return input;
+    }
+    std::list<T> ans;
+    ans.splice(ans.begin(), input, input.begin());
+    const T& pivot = *ans.begin();
+
+    auto divide_point = std::partition(input.begin(), input.end(), [&](const T& t){
+        return t < pivot;
+    });
+
+    std::list<T> lower_part;
+    lower_part.splice(lower_part.end(), input, input.begin(), divide_point);
+
+//    auto new_lower(seq_q_sort(std::move(lower_part)));
+    std::future<std::list<T>> new_lower(  // list前半部分操作由另一线程执行
+            std::async(&parallel_q_sort<T>, std::move(lower_part)));
+    auto new_higher(seq_q_sort(std::move(input)));
+
+    ans.splice(ans.end(), new_higher);
+    ans.splice(ans.begin(), new_lower.get());
+    return ans;
+}
+
+// spawn_task()
+template<typename F, typename A>
+std::future<typename std::result_of<F(A&&)>::type> spawn_task(F&& f, A&& a){
+    typedef typename std::result_of<F(A&&)>::type ans_type;
+    std::packaged_task<ans_type (A&&)> task(std::forward<F>(f));
+    std::future<ans_type> ans(task.get_future());
+    std::thread t(std::move(task), std::forward<A>(a));
+    t.detach();
+    return ans;
+}
\ No newline at end of file
-- 
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