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Make realization if the thread-safe priority queue #10
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<Project Sdk="Microsoft.NET.Sdk"> | ||
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<PropertyGroup> | ||
<TargetFramework>net6.0</TargetFramework> | ||
<Nullable>enable</Nullable> | ||
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<IsPackable>false</IsPackable> | ||
</PropertyGroup> | ||
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<ItemGroup> | ||
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" /> | ||
<PackageReference Include="NUnit" Version="3.13.2" /> | ||
<PackageReference Include="NUnit3TestAdapter" Version="4.0.0" /> | ||
<PackageReference Include="coverlet.collector" Version="3.1.0" /> | ||
</ItemGroup> | ||
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<ItemGroup> | ||
<ProjectReference Include="..\MyPriorityQueue\MyPriorityQueue.csproj" /> | ||
</ItemGroup> | ||
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</Project> |
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namespace MyPriorityQueue.Tests; | ||
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using MyPriorityQueue; | ||
using NUnit.Framework; | ||
using System.Collections.Generic; | ||
using System.Threading; | ||
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public class Tests | ||
{ | ||
[Test] | ||
public void EnqueueSizeAndDequeueFromOneThread() | ||
{ | ||
var priorityQueue = new PriorityQueue<int>(); | ||
priorityQueue.Enqueue(1231, -1); | ||
priorityQueue.Enqueue(1231, 1); | ||
Assert.AreEqual(2, priorityQueue.Size); | ||
priorityQueue.Enqueue(1, 23); | ||
Assert.AreEqual(3, priorityQueue.Size); | ||
Assert.AreEqual(1, priorityQueue.Dequeue()); | ||
Assert.AreEqual(2, priorityQueue.Size); | ||
priorityQueue.Enqueue(12, 1); | ||
Assert.AreEqual(3, priorityQueue.Size); | ||
Assert.AreEqual(1231, priorityQueue.Dequeue()); | ||
Assert.AreEqual(2, priorityQueue.Size); | ||
Assert.AreEqual(12, priorityQueue.Dequeue()); | ||
Assert.AreEqual(1, priorityQueue.Size); | ||
Assert.AreEqual(1231, priorityQueue.Dequeue()); | ||
Assert.AreEqual(0, priorityQueue.Size); | ||
} | ||
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[Test] | ||
public void EnqueueFromDifferentThreads() | ||
{ | ||
var priorityQueue = new PriorityQueue<int>(); | ||
var threads = new Thread[3]; | ||
for (int i = 0; i < threads.Length; ++i) | ||
{ | ||
var localI = i; | ||
threads[i] = new Thread(() => | ||
{ | ||
priorityQueue.Enqueue(localI, 1); | ||
}); | ||
} | ||
foreach (var thread in threads) | ||
{ | ||
thread.Start(); | ||
} | ||
foreach (var thread in threads) | ||
{ | ||
thread.Join(); | ||
} | ||
Assert.AreEqual(3, priorityQueue.Size); | ||
} | ||
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[Test] | ||
public void DequeueFromDifferentThreadsAndSavingFIFO() | ||
{ | ||
var priorityQueue = new PriorityQueue<string>(); | ||
priorityQueue.Enqueue("true", 1); | ||
priorityQueue.Enqueue("false", 1); | ||
priorityQueue.Enqueue("abobus", 1); | ||
var values = new string[3]; | ||
var threads = new Thread[3]; | ||
for (int i = 0; i < threads.Length; ++i) | ||
{ | ||
var localI = i; | ||
threads[i] = new Thread(() => | ||
{ | ||
values[localI] = priorityQueue.Dequeue(); | ||
}); | ||
} | ||
foreach (var thread in threads) | ||
{ | ||
thread.Start(); | ||
} | ||
foreach (var thread in threads) | ||
{ | ||
thread.Join(); | ||
} | ||
var correctValues = new string[3]; | ||
correctValues[0] = "true"; | ||
correctValues[1] = "false"; | ||
correctValues[2] = "abobus"; | ||
Assert.AreEqual(correctValues, values); | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Это не должно проходить :) Dequeue делается в разных потоках, и кто из них будет первым, тот и запишет в свою ячейку взятое из очереди значение. То есть даже если очередь возвращает всё как надо, values могут быть перемешанными |
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Assert.AreEqual(0, priorityQueue.Size); | ||
} | ||
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[Test] | ||
public void EnqueueAndDequeueFromDifferentThreadsWithoutExceptions() | ||
{ | ||
var priorityQueue = new PriorityQueue<string>(); | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Вынесли бы создание очереди в SetUp |
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var threads = new Thread[2]; | ||
threads[0] = new Thread(() => | ||
{ | ||
priorityQueue.Dequeue(); | ||
}); | ||
threads[1] = new Thread(() => | ||
{ | ||
priorityQueue.Enqueue("ololo", 131); | ||
}); | ||
foreach (var thread in threads) | ||
{ | ||
thread.Start(); | ||
} | ||
foreach (var thread in threads) | ||
{ | ||
thread.Join(); | ||
} | ||
Assert.AreEqual(0, priorityQueue.Size); | ||
} | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Всего два потока, всего один раз... |
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} |
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namespace MyPriorityQueue; | ||
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/// <summary> | ||
/// Interface of thread-safe priority queue | ||
/// </summary> | ||
/// <typeparam name="TValue">Type of value</typeparam> | ||
public interface IPriorityQueue<TValue> | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Интерфейс не просили, хотя сделать его — вряд ли ошибка :) |
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{ | ||
/// <summary> | ||
/// Add value ant its priority to the priority queue | ||
/// </summary> | ||
/// <param name="value">Given value</param> | ||
/// <param name="priority">Given priority</param> | ||
void Enqueue(TValue value, int priority); | ||
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/// <summary> | ||
/// Removes and returns the first founded value with the highest priority from the priority queue | ||
/// </summary> | ||
/// <returns>Value with the highest priority</returns> | ||
TValue Dequeue(); | ||
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/// <summary> | ||
/// Returns the quantity of elements | ||
/// </summary> | ||
int Size { get; } | ||
} |
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<Project Sdk="Microsoft.NET.Sdk"> | ||
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<PropertyGroup> | ||
<OutputType>Exe</OutputType> | ||
<TargetFramework>net6.0</TargetFramework> | ||
<ImplicitUsings>enable</ImplicitUsings> | ||
<Nullable>enable</Nullable> | ||
</PropertyGroup> | ||
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</Project> |
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| ||
Microsoft Visual Studio Solution File, Format Version 12.00 | ||
# Visual Studio Version 17 | ||
VisualStudioVersion = 17.1.32210.238 | ||
MinimumVisualStudioVersion = 10.0.40219.1 | ||
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MyPriorityQueue", "MyPriorityQueue.csproj", "{B1F6ADA8-0C8E-4016-912A-B0193040CA8D}" | ||
EndProject | ||
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MyPriorityQueue.Tests", "..\MyPriorityQueue.Tests\MyPriorityQueue.Tests.csproj", "{EA3D469B-6AD6-451A-9F64-D2479A4702A9}" | ||
EndProject | ||
Global | ||
GlobalSection(SolutionConfigurationPlatforms) = preSolution | ||
Debug|Any CPU = Debug|Any CPU | ||
Release|Any CPU = Release|Any CPU | ||
EndGlobalSection | ||
GlobalSection(ProjectConfigurationPlatforms) = postSolution | ||
{B1F6ADA8-0C8E-4016-912A-B0193040CA8D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU | ||
{B1F6ADA8-0C8E-4016-912A-B0193040CA8D}.Debug|Any CPU.Build.0 = Debug|Any CPU | ||
{B1F6ADA8-0C8E-4016-912A-B0193040CA8D}.Release|Any CPU.ActiveCfg = Release|Any CPU | ||
{B1F6ADA8-0C8E-4016-912A-B0193040CA8D}.Release|Any CPU.Build.0 = Release|Any CPU | ||
{EA3D469B-6AD6-451A-9F64-D2479A4702A9}.Debug|Any CPU.ActiveCfg = Debug|Any CPU | ||
{EA3D469B-6AD6-451A-9F64-D2479A4702A9}.Debug|Any CPU.Build.0 = Debug|Any CPU | ||
{EA3D469B-6AD6-451A-9F64-D2479A4702A9}.Release|Any CPU.ActiveCfg = Release|Any CPU | ||
{EA3D469B-6AD6-451A-9F64-D2479A4702A9}.Release|Any CPU.Build.0 = Release|Any CPU | ||
EndGlobalSection | ||
GlobalSection(SolutionProperties) = preSolution | ||
HideSolutionNode = FALSE | ||
EndGlobalSection | ||
GlobalSection(ExtensibilityGlobals) = postSolution | ||
SolutionGuid = {42B04315-5D4D-4FA7-9A03-E4C34222BD0B} | ||
EndGlobalSection | ||
EndGlobal |
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namespace MyPriorityQueue; | ||
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using System.Collections.Generic; | ||
using System.Linq; | ||
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/// <summary> | ||
/// Realisation of thread-safe priority queue interface | ||
/// </summary> | ||
/// <typeparam name="TValue">Type of value</typeparam> | ||
public class PriorityQueue<TValue> : IPriorityQueue<TValue> | ||
{ | ||
private readonly SortedList<int, Queue<TValue>> elementsByPriority = new(); | ||
private int counter = 0; | ||
private readonly object locker = new(); | ||
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public void Enqueue(TValue value, int priority) | ||
{ | ||
lock (locker) | ||
{ | ||
if (!elementsByPriority.ContainsKey(priority)) | ||
{ | ||
elementsByPriority[priority] = new Queue<TValue>(); | ||
} | ||
elementsByPriority[priority].Enqueue(value); | ||
counter++; | ||
Monitor.PulseAll(locker); | ||
} | ||
} | ||
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public TValue Dequeue() | ||
{ | ||
lock (locker) | ||
{ | ||
while (counter == 0) | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Кажется, counter должен быть volatile-полем, потому что этот поток может ещё не увидеть изменений из 25-й строки и снова встанет на Wait, будет дедлок. В .NET memory model вроде есть что-то про то, что взятие/освобождение замка влечёт синхронизацию памяти, так что на практике, скорее всего, всё будет хорошо, но мне кажется, лучше избегать таких проблем явно |
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{ | ||
Monitor.Wait(locker); | ||
} | ||
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var maxPriority = elementsByPriority.Keys.Last(); | ||
var element = elementsByPriority[maxPriority].Dequeue(); | ||
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if (elementsByPriority[maxPriority].Count == 0) | ||
{ | ||
elementsByPriority.Remove(maxPriority); | ||
} | ||
counter--; | ||
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return element; | ||
} | ||
} | ||
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public int Size => counter; | ||
} |
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namespace MyPriorityQueue; | ||
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public static class Program | ||
{ | ||
public static void Main(string[] args) | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Это не нужно. Как метод Main в современном .NET, так и точка входа в проекте, который по сути является библиотекой |
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{ | ||
} | ||
} |
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
new Thread в современном .NET не нужен, есть пул потоков и Task.Run (или более высокоуровневые вещи, типа Parallel.ForEach)