Примож Габриэльчич - Высокая производительность Delphi (черновик перевода глав 1-2)

Chapter 3, Fine-Tuning the Code, deals with lots of small things. Sometimes, performance lies in many small details, and this chapter shows how to use them to your advantage. We'll check the Delphi compiler settings and see which ones affect the code speed. We'll look at the implementation details for built-in data types and method calls. Using a correct type in a right way can mean a lot. Of course, we won't forget about the practical side. This chapter will give examples of different optimization techniques, such as extracting common expressions, using pointers to manipulate data, and implementing parts of the solution in assembler. At the end, we'll revisit the code from Chapter 1, About Performance, and make it even faster.

Chapter 4, Memory Management, is all about memory. It starts with a discussion on strings, arrays, and how their memory is managed. After that, we will move to the memory functions exposed by Delphi. We'll see how we can use them to manage memory. Next, we'll cover records—how to allocate them, how to initialize them, and how to create useful dynamically-allocated generic records. We'll then move into the murky waters of memory manager implementation. I'll sketch a very rough overview of FastMM, the default memory manager in Delphi. First, I'll explain why FastMM is excellent and then I'll show when and why it may slow you down. We'll see how to analyze memory performance problems and how to switch the memory manager for a different one. In the last part, we'll revisit the SlowCode program and reduce the number of memory allocations it makes.

Chapter 5, Getting Started with the Parallel World, moves the topic to parallel programming. In the introduction, I'll talk about processes and threads, and multithreading and multitasking to establish some common ground for discussion. After that, you'll start learning what not to do when writing parallel code. I'll explain how the user interface must be handled from background threads and what problems are caused by sharing data between threads. Then, I'll start fixing those problems by implementing various kinds of synchronization mechanisms and interlocked operations. We'll also deal with the biggest problem synchronization brings to the code—deadlocking. As synchronization inevitably slows the program down, I'll explain how to achieve the highest possible speed using data duplication, aggregation, and communication. At the end, I'll introduce two third-party libraries that contain helpful parallel functions and data structures.

Chapter 6, Working with Parallel Tools, focuses on a single topic, Delphi's TThread class. In the introduction, I'll explain why I believe that TThread is still important even in this modern age. I will explore different ways in which TThread based threads can be managed in your code. After that, I'll go through the most important TThread methods and properties and explain what they're good for. In the second part of the chapter, I'll extend TThread into something more modern and easier to use. Firstly, I'll add a communication channel so that you'll be able to send messages to the thread. After that, I'll implement a derived class designed to handle one specific usage pattern and show how this approach simplifies writing parallel code to the extreme.

Chapter 7, Exploring Parallel Practices, moves the multithreaded programming to more abstract terms. In this chapter, I'll discuss modern multithreading concepts: tasks and patterns. I'll look into Delphi's own implementation, Parallel Programming Library, and demonstrate the use of TTask/ITask. We'll look at topics such as task management, exception handling, and thread pooling. After that, I'll move on to patterns and talk about all Parallel Programming Library patterns: Join, Future, and Parallel For. I will also introduce two custom patterns—Async/Await and Join/Await—and finish the chapter with a discussion on the Pipeline pattern from OmniThreadLibrary.

Chapter 8, Using External Libraries, admits that sometimes Delphi is not enough. Sometimes the problem is too complicated to be efficiently solved by a human. Sometimes Pascal is just lacking the speed. In such cases, we can try finding an existing library that solves our problem. In most cases, it will not support Delphi directly but will provide some kind of C or C++ interface. This chapter looks into linking with C object files and describes typical problems that you'll encounter on the way. In the second half, I'll present a complete example of linking to a C++ library, from writing a proxy DLL to using it in Delphi.

Chapter 9, Best Practices, wraps it all up. In this last chapter, I'll revisit all the important topics I explored in previous chapters. At the same time, I'll drop in some additional tips, tricks, and techniques.

To get the most out of this book

Although you can read this book in bed or on the beach, you will need a computer and Delphi to play with the code examples. The code was written in Delphi 10.2 Tokyo, but it should also work without a problem in the older versions. I did use some modern features in demos—and dedicated a chapter to Parallel Programming Library that was introduced in Delphi XE7—so anything older than that is hit and miss.

This book does not refer to any functionality specific to the Enterprise edition. You'll be able to test all the code with the entry-level professional edition.

Download the example code files

You can download the example code files for this book from your account at www.packtpub.com. If you purchased this book elsewhere, you can visit www.packtpub.com/support and register to have the files emailed directly to you.

You can download the code files by following these steps:

Log in or register at www.packtpub.com.

Select the SUPPORT tab.

Click on Code Downloads & Errata.

Enter the name of the book in the Search box and follow the onscreen instructions.

Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of:

WinRAR/7-Zip for Windows

Zipeg/iZip/UnRarX for Mac

7-Zip/PeaZip for Linux

The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Delphi-High-Performance/. In case there's an update to the code, it will be updated on the existing GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

Conventions used

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "A string parameter value is present in a string list."

A block of code is set as follows:

function IsPresentInList(strings: TStrings; const value: string): Boolean;

var

i: Integer;

begin

Result := False;

for i := 0 to strings.Count - 1 do

if SameText(strings[i], value) then

Exit(True);

end;

Bold: Indicates a new term, an important word, or words that you see onscreen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "Go to Options | Options, then select General | Search directory."

Warnings or important notes appear like this.

Tips and tricks appear like this.

Get in touch

Feedback from our readers is always welcome.

General feedback: Email --">