Hands-On Parallel Programming with C# 8 and .NET Core 3: Build solid enterprise software using task parallelism and multithreading

Cover....1

Title Page....2

Copyright and Credits....3

Dedication....4

About Packt....5

Contributors....6

Table of Contents....8

Preface....16

Section 1: Fundamentals of Threading, Multitasking, and Asynchrony....21

Chapter 1: Introduction to Parallel Programming....22

Technical requirements....23

Preparing for multi-core computing....23

Processes....23

Some more information about the OS....24

Multitasking....24

Hyper-threading....24

Flynn's taxonomy....26

Threads....27

Types of threads....27

Apartment state....27

Multithreading....30

Thread class....32

Advantages and disadvantages of threads....36

The ThreadPool class....36

Advantages, disadvantages, and when to avoid using ThreadPool....39

BackgroundWorker....40

Advantages and disadvantages of using BackgroundWorker....44

Multithreading versus multitasking....44

Scenarios where parallel programming can come in handy....45

Advantages and disadvantages of parallel programming ....45

Summary....46

Questions....47

Chapter 2: Task Parallelism....48

Technical requirements....49

Tasks....49

Creating and starting a task....50

The System.Threading.Tasks.Task class....50

Using lambda expressions syntax....51

Using the Action delegate....51

Using delegate....51

The System.Threading.Tasks.Task.Factory.StartNew method....52

Using lambda expressions syntax....52

Using the Action delegate....52

Using delegate....52

The System.Threading.Tasks.Task.Run method....53

Using lambda expressions syntax....53

Using the Action delegate....53

Using delegate....53

The System.Threading.Tasks.Task.Delay method....54

The System.Threading.Tasks.Task.Yield method....55

The System.Threading.Tasks.Task.FromResult method....58

The System.Threading.Tasks.Task.FromException and System.Threading.Tasks.Task.FromException methods....59

The System.Threading.Tasks.Task.FromCanceled and System.Threading.Tasks.Task.FromCanceled methods....59

Getting results from finished tasks....60

How to cancel tasks....61

Creating a token....62

Creating a task using tokens....62

Polling the status of the token via the IsCancellationRequested property ....62

Registering for a request cancellation using the Callback delegate....63

How to wait on running tasks....65

Task.Wait....66

Task.WaitAll....67

Task.WaitAny....67

Task.WhenAll....68

Task.WhenAny....68

Handling task exceptions....69

Handling exception from single tasks....69

Handling exceptions from multiple tasks....70

Handling task exceptions with a callback function....71

Converting APM patterns into tasks....72

Converting EAPs into tasks....74

More on tasks....76

Continuation tasks....76

Continuing tasks using the Task.ContinueWith method....76

Continuing tasks using Task.Factory.ContinueWhenAll and Task.Factory.ContinueWhenAll....78

Continuing tasks using Task.Factory.ContinueWhenAny and Task.Factory.ContinueWhenAny....78

Parent and child tasks....79

Creating a detached task....79

Creating an attached task....80

Work-stealing queues....81

Summary....84

Chapter 3: Implementing Data Parallelism....85

Technical requirements....85

Moving from sequential loops to parallel loops....86

Using the Parallel.Invoke method....87

Using the Parallel.For method....89

Using the Parallel.ForEach method....90

Understanding the degree of parallelism....91

Creating a custom partitioning strategy....93

Range partitioning....94

Chunk partitioning....94

Canceling loops....95

Using the Parallel.Break method....96

Using ParallelLoopState.Stop....98

Using CancellationToken to cancel loops....98

Understanding thread storage in parallel loops....100

Thread local variable....101

Partition local variable....102

Summary....103

Questions....104

Chapter 4: Using PLINQ....105

Technical requirements....105

LINQ providers in .NET....106

Writing PLINQ queries....107

Introducing the ParallelEnumerable class....107

Our first PLINQ query....108

Preserving order in PLINQ while doing parallel executions....109

Sequential execution using the AsUnOrdered() method....110

Merge options in PLINQ....111

Using the NotBuffered merge option....111

Using the AutoBuffered merge option....112

Using the FullyBuffered merge option....113

Throwing and handling exceptions with PLINQ....115

Combining parallel and sequential LINQ queries....118

Canceling PLINQ queries....119

Disadvantages of parallel programming with PLINQ....120

Understanding the factors that affect the performance of PLINQ (speedups)....121

Degree of parallelism....121

Merge option....121

Partitioning type....121

Deciding when to stay sequential with PLINQ....122

Order of operation....122

ForAll versus calling ToArray() or ToList()....123

Forcing parallelism....123

Generating sequences....123

Summary....124

Questions....124

Section 2: Data Structures that Support Parallelism in .NET Core....126

Chapter 5: Synchronization Primitives....127

Technical requirements....128

What are synchronization primitives?....128

Interlocked operations ....129

Memory barriers in .NET....130

What is reordering? ....131

Types of memory barriers....132

Avoiding code reordering using constructs....133

Introduction to locking primitives....134

How locking works....134

Thread state....135

Blocking versus spinning....136

Lock, mutex, and semaphore....137

Lock....137

Mutex....140

Semaphore....142

Local semaphore....143

Global semaphore....144

ReaderWriterLock....144

Introduction to signaling primitives....144

Thread.Join....145

EventWaitHandle....146

AutoResetEvent....146

ManualResetEvent....147

WaitHandles....150

Lightweight synchronization primitives....153

Slim locks....153

ReaderWriterLockSlim....154

SemaphoreSlim....156

ManualResetEventSlim....156

Barrier and countdown events....157

A case study using Barrier and CountDownEvent....157

SpinWait....160

SpinLock....161

Summary....162

Questions....163

Chapter 6: Using Concurrent Collections....164

Technical requirements....164

An introduction to concurrent collections....165

Introducing IProducerConsumerCollection....165

Using ConcurrentQueue....166

Using queues to solve a producer-consumer problem....167

Solving problems using concurrent queues....168

Performance consideration – Queue versus ConcurrentQueue....169

Using ConcurrentStack....170

Creating a concurrent stack....170

Using ConcurrentBag....171

Using BlockingCollection....173

Creating BlockingCollection....173

A multiple producer-consumer scenario....175

Using ConcurrentDictionary....176

Summary....178

Questions....179

Chapter 7: Improving Performance with Lazy Initialization....180

Technical requirements....180

Introducing lazy initialization concepts....181

Introducing System.Lazy....184

Construction logic encapsulated inside a constructor....184

Construction logic passed as a delegate to Lazy....186

Handling exceptions with the lazy initialization pattern....187

No exceptions occur during initialization....187

Random exception while initialization with exception caching....187

Not caching exceptions....190

Lazy initialization with thread-local storage....191

Reducing the overhead with lazy initializations....193

Summary....196

Questions....197

Section 3: Asynchronous Programming Using C#....198

Chapter 8: Introduction to Asynchronous Programming....199

Technical requirements....199

Types of program execution....200

Understanding synchronous program execution....200

Understanding asynchronous program execution....202

When to use asynchronous programming....203

Writing asynchronous code....203

Using the BeginInvoke method of the Delegate class....204

Using the Task class....205

Using the IAsyncResult interface....206

When not to use asynchronous programming....208

In a single database without connection pooling....208

When it is important that the code is easy to read and maintain....208

For simple and short-running operations....208

For applications with lots of shared resources....209

Problems you can solve using asynchronous code....209

Summary....210

Questions....211

Chapter 9: Async, Await, and Task-Based Asynchronous Programming Basics....212

Technical requirements....213

Introducing async and await....213

The return type of async methods....217

Async delegates and lambda expressions....218

Task-based asynchronous patterns....219

The compiler method, using the async keyword....219

Implementing the TAP manually....219

Exception handling with async code....220

A method that returns Task and throws an exception....220

An async method from outside a try-catch block without the await keyword....221

An async method from inside the try-catch block without the await keyword....223

Calling an async method with the await keyword from outside the try-catch block....225

Methods returning void....226

Async with PLINQ....227

Measuring the performance of async code....228

Guidelines for using async code....231

Avoid using async void....231

Async chain all the way....231

Using ConfigureAwait wherever possible....232

Summary....233

Questions....233

Section 4: Debugging, Diagnostics, and Unit Testing for Async Code....235

Chapter 10: Debugging Tasks Using Visual Studio....236

Technical requirements....237

Debugging with VS 2019 ....237

How to debug threads....237

Using Parallel Stacks windows....241

Debugging using Parallel Stacks windows....241

Threads view....242

Tasks view....243

Debugging using the Parallel Watch window....244

Using Concurrency Visualizer....246

Utilization view....247

Threads view....248

Cores view....249

Summary....249

Questions....250

Further reading ....250

Chapter 11: Writing Unit Test Cases for Parallel and Asynchronous Code....251

Technical requirements....252

Unit testing with .NET Core....252

Understanding the problems with writing unit test cases for async code....254

Writing unit test cases for parallel and async code....257

Checking for a successful result....257

Checking for an exception result when the divisor is 0....258

Mocking the setup for async code using Moq....258

Testing tools....261

Summary....262

Questions ....262

Further reading....263

Section 5: Parallel Programming Feature Additions to .NET Core....264

Chapter 12: IIS and Kestrel in ASP.NET Core....265

Technical requirements....265

IIS threading model and internals....266

Starvation Avoidance....267

Hill Climbing....267

Kestrel threading model and internals....268

ASP.NET Core 1.x....269

ASP.NET Core 2.x....270

Introducing the best practices of threading in microservices....271

Single thread-single process microservices....271

Single thread-multiple process microservices....272

Multiple threads-single process....272

Asynchronous services....272

Dedicated thread pools....272

Introducing async in ASP.NET MVC core....273

Async streams ....277

Summary....280

Questions....281

Chapter 13: Patterns in Parallel Programming....282

Technical requirements....282

The MapReduce pattern....283

Implementing MapReduce using LINQ....283

Aggregation....286

The fork/join pattern....288

The speculative processing pattern....288

The lazy pattern....290

Shared state pattern....293

Summary....293

Questions....294

Chapter 14: Distributed Memory Management....295

Technical requirements....296

Introduction to distributed systems....296

Shared versus distributed memory model....297

Shared memory model....298

Distributed memory model....300

Types of communication network....301

Static communication networks....301

Dynamic communication networks....302

Properties of communication networks....302

Topology....302

Routing algorithms....303

Switching strategy....304

Flow control....304

Exploring topologies....305

Linear and ring topologies....305

Linear arrays....305

Ring or torus....306

Meshes and tori....306

2D mesh....307

2D torus....308

Programming distributed memory machines using message passing....308

Why MPI?....309

Installing MPI on Windows....309

Sample program using MPI....309

Basic send/receive use....310

Collectives....312

Summary....312

Questions....313

Assessments....314

Other Books You May Enjoy....318

Index....321

This book is for C# programmers who want to learn multithreading and parallel programming concepts and want to use them in enterprise applications built using .NET Core. It is also designed for students and professionals who simply want to learn about how parallel programming works with modern-day hardware.It is assumed that you already have some familiarity with the C# programming language and some basic knowledge of how OSes work.