#### 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

## Returning to SlowCode

At the end of this chapter, I'll return to the now well-known `SlowCode` example. At the end of the previous chapter, we significantly adapted the code and ended with a version that calculates prime numbers with the Sieve of Eratosthenes (`SlowCode_Sieve`). That version processed 10 million numbers in 1,072 milliseconds. Let's see if we can improve that.

The obvious target for optimization is the `Reverse` function which creates the result by appending characters one at a time. We've seen in this chapter that modifying a string can cause frequent memory allocations:

```function Reverse(s: string): string;
var
ch: char;
begin
Result := '';
for ch in s do
Result := ch + Result;
end;```

Instead of optimizing this function, let's look at how it is used. The `Filter` method uses it to reverse a number:

`reversed := StrToInt(Reverse(IntToStr(i)));`

This statement brings in another memory allocation (in function `IntToStr` which creates a new string), and executes some code that has to...