Différences

Ci-dessous, les différences entre deux révisions de la page.

--- developpement:dotnet:csharp:introduction [2023/10/04 02:10] – [Signaling] sgariepy
+++ developpement:dotnet:csharp:introduction [2023/10/06 05:06] (Version actuelle) – [Reactive] sgariepy
@@ Ligne 1148: / Ligne 1148: @@
+===== Manual Event Reset =====
+<code csharp>
+static ManualResetEvent customEvent = new ManualResetEvent(false);
+// Equivalent: static EventWaitHandle eventWaitHandle = new EventWaitHandle(false, EventResetMode.ManualReset);
+void Main()
+{
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Thread.Sleep(1000);
+    Console.WriteLine("Press a key to release all the threads");
+    Console.Read();
+    customEvent.Set();
+    Thread.Sleep(1000);
+    Console.WriteLine("Press a key again.  Thread won't block even if they call WaitOne");
+    Console.Read();
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Thread.Sleep(1000);
+    Console.WriteLine("Press a key again.  Thread will block if they call WaitOne");
+    Console.Read();
+    customEvent.Reset();
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Task.Factory.StartNew(CallWaitOne);
+    Thread.Sleep(1000);
+    Console.WriteLine("Press a key again calls Set()");
+    Console.Read();
+    customEvent.Set();
+    Console.ReadLine();
+}
+void CallWaitOne()
+{
+    Console.WriteLine("{0} has called WaitOne", Task.CurrentId);
+    customEvent.WaitOne();
+    Console.WriteLine("{0} finally ended", Task.CurrentId);
+}
+</code>
+===== Countdown =====
+<code csharp>
+static CountdownEvent customCountdown = new CountdownEvent(5);
+void Main()
+{
+    Task.Factory.StartNew(DoSomething);
+    Task.Factory.StartNew(DoSomething);
+    Task.Factory.StartNew(DoSomething);
+    Task.Factory.StartNew(DoSomething);
+    Task.Factory.StartNew(DoSomething);
+    customCountdown.Wait();
+    Console.WriteLine("Signal has been called 5 times");
+}
+void DoSomething()
+{
+    Thread.Sleep(250);
+    Console.WriteLine("{0} is calling signal", Task.CurrentId);
+    customCountdown.Signal();
+}
+</code>
+====== Task Parallel Library (TPL) ======
+  * Set of public types and APIs that can be found in two namespaces:
+    * System.Threading
+    * System.Threading.Tasks
+  * Simplifies process of adding parallelism and concurrency to applications
+  * Value is ability to scale degree of concurrency dynamically
+  * Handles partitioning of work
+  * Schedules threads on ThreadPool
+  * Allows for task cancellation
+  * Handles state management
+  * Not all code is suitable for parallelization
+  * Threading of any type has an associated overhead
+  * In some cases, multithreading may be slower than sequential code
+Exemple simple:
+<code csharp>
+void Main()
+{
+    Stopwatch stopwatch = new Stopwatch();
+    stopwatch.Start();
+    for (int i = 0; i < 10; i++)
+    {
+        Console.WriteLine(i);
+    }
+    stopwatch.Stop();
+    Console.WriteLine("Time taken: {0}", stopwatch.ElapsedTicks);
+    stopwatch.Start();
+    Parallel.For(0, 10, i => {
+        Console.WriteLine(i);
+    });
+    stopwatch.Stop();
+    Console.WriteLine("Time taken: {0}", stopwatch.ElapsedTicks);
+}
+</code>
+Le cas en parallèle prend plus de temps dû au overhead.  L'instruction n'étant pas assez complexe pour justifier la parallèlisation.
+<code csharp>
+// Générer des images: https://picsum.photos/3840/2160
+void Main()
+{
+    var path = Directory.GetCurrentDirectory();
+    var files = Directory.GetFiles(path + @"\pictures", "*.jpg");
+    var normalAlteredPath = path + @"\normalAlteredPath";
+    var parallelAlteredPath = path + @"\parallelAlteredPath";
+    Directory.CreateDirectory(normalAlteredPath);
+    Directory.CreateDirectory(parallelAlteredPath);
+    ParallelExecutionMode(files, normalAlteredPath);
+    NormalExecutionMode(files, parallelAlteredPath);
+}
+void NormalExecutionMode(string[] files, string alteredPath)
+{
+    Stopwatch stopwatch = Stopwatch.StartNew();
+    foreach (var currentFile in files)
+    {
+        var file = Path.GetFileName(currentFile);
+        using (var fileBitmap = new Bitmap(currentFile))
+        {
+            fileBitmap.RotateFlip(RotateFlipType.Rotate270FlipX);
+            fileBitmap.Save(Path.Combine(alteredPath, file));
+            Console.WriteLine("Thread {0}", Thread.CurrentThread.ManagedThreadId);
+        }
+    }
+    Console.WriteLine("Normal execution time: {0}", stopwatch.ElapsedMilliseconds);
+    stopwatch.Stop();
+}
+void ParallelExecutionMode(string[] files, string alteredPath)
+{
+    Stopwatch stopwatch = Stopwatch.StartNew();
+    Parallel.ForEach(files, currentFile => {
+        var file = Path.GetFileName(currentFile);
+        using (var fileBitmap = new Bitmap(currentFile))
+        {
+            fileBitmap.RotateFlip(RotateFlipType.Rotate270FlipX);
+            fileBitmap.Save(Path.Combine(alteredPath, file));
+            Console.WriteLine("Thread {0}", Thread.CurrentThread.ManagedThreadId);
+        }
+    });
+    Console.WriteLine("Parallel execution time: {0}", stopwatch.ElapsedMilliseconds);
+    stopwatch.Stop();
+}
+</code>
+<code csharp>
+void Main()
+{
+    var list = Enumerable.Range(0, 100000000).ToArray();
+    CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
+    ParallelOptions parallelOptions = new ParallelOptions();
+    parallelOptions.CancellationToken = cancellationTokenSource.Token;
+    parallelOptions.MaxDegreeOfParallelism = System.Environment.ProcessorCount;
+    Console.WriteLine("Press 'x' to cancel");
+    Task.Factory.StartNew(() =>
+    {
+        if (Console.ReadLine() == "x")
+        {
+            cancellationTokenSource.Cancel();
+        }
+        long total = 0;
+        try
+        {
+            Parallel.For<long>(0, list.Length, parallelOptions, () => 0, (count, parallelLoopState, subtotal) =>
+            {
+                Thread.Sleep(200);
+                parallelOptions.CancellationToken.ThrowIfCancellationRequested();
+                subtotal += list[count];
+                return subtotal;
+            },
+            (x) =>
+            {
+                Interlocked.Add(ref total, x);
+            });
+        }
+        catch (OperationCanceledException ex)
+        {
+            Console.WriteLine("Cancelled " + ex.Message);
+        }
+        finally
+        {
+            cancellationTokenSource.Dispose();
+        }
+        Console.WriteLine("The final sum is {0}", total);
+    });
+}
+</code>
+===== Continuation with state =====
+<code csharp>
+void Main()
+{
+    Task<DateTime> task = Task.Run(() => DoSomething());
+    List<Task<DateTime>> continuationTasks = new List<Task<DateTime>>();
+    for (int i = 0; i < 3; i++)
+    {
+        task = task.ContinueWith((x, y) => DoSomething(), new Person { Id = i });
+        continuationTasks.Add(task);
+    }
+    task.Wait();
+    foreach (var continuation in continuationTasks)
+    {
+        Person person = continuation.AsyncState as Person;
+        Console.WriteLine("Task finished at " + continuation.Result + ". Person id is {0}", person.Id);
+    }
+}
+static DateTime DoSomething()
+{
+    return DateTime.Now;
+}
+internal class Person
+{
+    public int Id { get; set; }
+}
+</code>
+===== TaskCompletionSource =====
+<code csharp>
+void Main()
+{
+    TaskCompletionSource<Product> taskCompletionSource = new TaskCompletionSource<Product>();
+    Task<Product> lazyTask = taskCompletionSource.Task;
+    Task.Factory.StartNew(() => {
+        Thread.Sleep(2000);
+        taskCompletionSource.SetResult(new Product { Id = 1, Name = "Some name" });
+    });
+    Task.Factory.StartNew(() =>
+    {
+        if (Console.ReadLine() == "x")
+        {
+            Product result = lazyTask.Result;
+            Console.WriteLine("Result is {0}", result.Name);
+        }
+    });
+    Thread.Sleep(5000);
+}
+class Product
+{
+    public int Id { get; set; }
+    public string Name { get; set; }
+}
+</code>
+===== PLINQ =====
+Parallel LINQ:
+  * Automates parallelization
+  * Considéré déclaratif plutôt qu'impératif
+  * Opérateurs qui font en sorte que ce n'est pas parallélisé:
+    * Take, Select, SelectMany, Skip, TakeWhile, SkipWhile, ElementAt
+  * Anomalies
+    * Join, GroupBy, GroupJoin, Distinct, Union, Intersect, Except
+  * Force parallelism:
+    * .AsParallel().withExecutionMode(ParallelExecution.ForceParallelism)
+<code csharp>
+void Main()
+{
+    var list = Enumerable.Range(1, 100000);
+    var primeNumbers = list
+                        .AsParallel()
+                        .Where(IsPrime);
+    Console.WriteLine("{0} prime numbers", primeNumbers.Count());
+}
+bool IsPrime(int x)
+{
+    if (x == 1) return false;
+    if (x == 2) return true;
+    if (x % 2 == 0) return false;
+    var boundary = (int)Math.Floor(Math.Sqrt(x));
+    for (int i = 3; i <= boundary; i += 2)
+    {
+        if (x % i == 0)
+        {
+            return false;
+        }
+    }
+    return true;
+}
+</code>
+==== Degree of Parallelism ====
+<code csharp>
+void Main()
+{
+    List<string> websites = new List<string>();
+    websites.Add("apple.com");
+    websites.Add("google.com");
+    websites.Add("microsoft.com");
+    List<PingReply> responses = websites
+                                    .AsParallel()
+                                    .WithDegreeOfParallelism(websites.Count())
+                                    .Select(PingSites)
+                                    .ToList();
+    foreach (var response in responses)
+    {
+        Console.WriteLine(response.Address + " " + response.Status + " " + response.RoundtripTime);
+    }
+    Console.ReadLine();
+}
+private static PingReply PingSites(string websiteName)
+{
+    Ping ping = new Ping();
+    return ping.Send(websiteName);
+}
+</code>
+====== Thread Marshalling ======
+  * [[http://bigballofmud.wordpress.com/2009/03/21/thread-marshalling-part-1-creating-a-thread-in-windows-forms/|Thread Marshalling]]
+  * [[http://www.albahari.com/threading/|Threading (Joseph Albahari)]]
+====== Pattern Matching ======
+<code csharp>
+void Main()
+{
+    var circle = new Circle(5);
+    var circleRadius100 = new Circle(250);
+    var rectangle = new Rectangle(420, 1337);
+    var square = new Rectangle(70, 70);
+    var shapes = new List<Shape> { circle, circleRadius100, rectangle, square };
+    var randomShape = shapes[new Random().Next(shapes.Count)];
+    CSharp6Feature(randomShape);
+    CSharp7Feature(randomShape);
+    CSharp8Feature(randomShape);
+    CSharp9Feature(randomShape);
+}
+private void CSharp6Feature(Shape shape)
+{
+    Console.WriteLine("=== C# 6 Pattern matching features ===");
+    if (shape is Circle) // 'is' operator
+    {
+        var circle = (Circle)shape;
+        Console.WriteLine($"Circle with radius {circle.Radius}");
+    }
+    else
+    {
+        Console.WriteLine($"Shape is something else");
+    }
+}
+private void CSharp7Feature(Shape shape)
+{
+    Console.WriteLine("=== C# 7 Pattern matching features ===");
+    if (shape is Circle circle)  // implicit casting
+    {
+        Console.WriteLine($"Circle with radius {circle.Radius}");
+    }
+    else
+    {
+        Console.WriteLine($"Shape is something else");
+    }
+    // using switch
+    switch (shape)
+    {
+        case Circle c:
+            Console.WriteLine($"Circle with radius {c.Radius}");
+            break;
+        case Rectangle r when r.Height == r.Width:
+            Console.WriteLine($"This is a square");
+            break;
+        default:
+            Console.WriteLine($"Shape is something else");
+            break;
+    }
+}
+private void CSharp8Feature(Shape shape)
+{
+    Console.WriteLine("=== C# 8 Pattern matching features ===");
+    if (shape is Circle { Radius: 10 })
+    {
+        Console.WriteLine($"Circle with radius of 10");
+    }
+    var shapeDetails = shape switch
+    {
+        Circle => "This is a circle", // we can drop the 'cir' is not used
+        Rectangle rec when rec.Height == rec.Width => "This is a square",
+        _ => "Shape is something else"
+    };
+}
+private void CSharp9Feature(Shape shape)
+{
+    Console.WriteLine("=== C# 9 Pattern matching features ===");
+    if (shape is not Rectangle) // 'not' added
+    {
+        Console.WriteLine($"This is not a rectangle");
+    }
+    if (shape is Circle { Radius: > 100 and < 200, Area: >= 1000 })
+    {
+        Console.WriteLine($"Circle with radius greater than 100");
+    }
+    // that can be used like so: if (shape is not null) {...}
+    var shapeDetails = shape switch
+    {
+        Circle => "This is a circle", // we can drop the 'cir' is not used
+        Rectangle rec when rec.Height == rec.Width => "This is a square",
+        { Area: 100 } => "Area is 100",
+        _ => "Shape is something else"
+    };
+    var areaDetails = shape.Area switch
+    {
+        >= 100 and <= 200 => "Area is between 100 and 200",
+        _ => ""
+    };
+}
+public static class Extensions
+{
+    public static bool IsLetter(this char c) =>
+        c is >= 'a' and <= 'z' or >= 'A' and <= 'Z';
+}
+public abstract class Shape
+{
+    public abstract double Area { get; }
+}
+public class Rectangle : Shape, ISquare
+{
+    public Rectangle(int height, int width)
+    {
+        Height = height;
+        Width = width;
+    }
+    public override double Area => Height * Width;
+    public int Height { get; set; }
+    public int Width { get; set; }
+}
+public class Circle : Shape
+{
+    private const double PI = Math.PI;
+    public Circle(int diameter)
+    {
+        Diameter = diameter;
+    }
+    public int Diameter { get; set; }
+    public int Radius => Diameter / 2;
+    public override double Area => PI * Radius * Radius;
+}
+public interface ISquare
+{
+    int Height { get; set; }
+    int Width { get; set; }
+}
+static decimal GetGroupTicketPriceDiscount(int groupSize, DateTime visitDate)
+    => (groupSize, visitDate.DayOfWeek) switch
+    {
+        (<= 0, _) => throw new ArgumentException("Group size must be positive"),
+        (_, DayOfWeek.Saturday or DayOfWeek.Sunday) => 0.0m,
+        (>= 5 and < 10, DayOfWeek.Monday) => 20.0m,
+        (>= 10, DayOfWeek.Monday) => 30.0m,
+        (>= 5 and < 10, _) => 12.0m,
+        (>= 10, _) => 15.0m,
+        _ => 0.0m
+    };
+</code>
@@ Ligne 1194: / Ligne 1742: @@
-====== Thread Marshalling ======
-  * [[http://bigballofmud.wordpress.com/2009/03/21/thread-marshalling-part-1-creating-a-thread-in-windows-forms/|Thread Marshalling]]
-  * [[http://www.albahari.com/threading/|Threading (Joseph Albahari)]]