#### Overview of this book

Delphi is a cross-platform Integrated Development Environment (IDE) that supports rapid application development for Microsoft Windows, Apple Mac OS X, Google Android, iOS, and now Linux with RAD Studio 10.2. This book will be your guide to build efficient high performance applications with Delphi. The book begins by explaining how to find performance bottlenecks and apply the correct algorithm to fix them. It will teach you how to improve your algorithms before taking you through parallel programming. You’ll then explore various tools to build highly concurrent applications. After that, you’ll delve into improving the performance of your code and master cross-platform RTL improvements. Finally, we’ll go through memory management with Delphi and you’ll see how to leverage several external libraries to write better performing programs. By the end of the book, you’ll have the knowledge to create high performance applications with Delphi.
Title Page
Packt Upsell
Contributors
Preface
Free Chapter
Fixing the Algorithm
Fine-Tuning the Code
Memory Management
Getting Started with the Parallel World
Working with Parallel Tools
Exploring Parallel Practices
Using External Libraries
Best Practices
Other Books You May Enjoy
Index

## Speeding up SlowCode

For the last practical example, we can try speeding up Mr. Smith's `SlowCode` from Chapter 1, About Performance. Here, we immediately ran into a problem. To fix or change an algorithm we must understand what the code does. This happens a lot in practice, especially when you inherit some code. Reading and understanding code that you didn't write is an important skill.

Let's try to understand the first part of `SlowCode`. The `for` loop in `SlowMethod` starts counting with 2. Then it calls `ElementInDataDivides`, which does nothing as the `data` list is empty. Next, `SlowMethod` adds 2 to the list.

Next, `i` takes the value of 3. `ElementInDataDivides` checks if 3 is divisible by 2. It is not, so `SlowMethod` adds 3 to the list.

In the next step, i = 4, it is divisible by 2, and 4 is not added to the list. 5 is then added to the list (it is not divisible by 2 or 3), 6 is not (divisible by 2), 7 is added (not divisible by 2, 3, or 5), 8 is not (divisible by 2), 9 is not (divisible by 3), and...