This book has been written to be a practical guide to improving the performance of your Julia code. As such, we encourage you to run the code shown in this book yourself. Running the code and inspecting the output for yourself is the best way to learn the methods suggested here. All the code is available in machine-readable format (see the following for download instructions), so we suggest having a Julia REPL open while you read this book, so that you can copy and paste code on to it. 

You can view and download all code for this book at https://juliahighperformance.com. 

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

You can download the code files by following these steps:

1. Log in or register at www.packt.com.
2. Select the SUPPORT tab.
3. Click on Code Downloads & Errata.
4. 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/Julia-High-Performance-Second-Edition. 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!

We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: https://www.packtpub.com/sites/default/files/downloads/9781788298117_ColorImages.pdf.

Click on the following link to see the Code in Action: http://bit.ly/2WsMomd

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

CodeInText: Indicates code words in text, function or method names, folder names, and filenames. Here is an example: "Mount the downloaded WebStorm-10*.dmg disk image file as another disk in your system."

A block of code is set as follows:

struct Pixel{T} 
    x::Int64 
    y::Int64 
    color::T 
end

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

function sum_cols_matrix(x) 
   num_cols = size(x, 2) 
   s = zeros(num_cols) 
   for i = 1:num_cols 
      s[i] = sum_vector(x[:, i]) 
  end 
  return s 
end 

Most code snippets in this book have been typed at the Julia REPL. This is denoted by the julia> prompt. Such a listing will show the output of the expression below the expression itself. If you type the code into the REPL yourself, this is exactly what you should see:

julia> a = fill(1, 4,4)
4×4 Array{Int64,2}:
 1 1 1 1
 1 1 1 1
 1 1 1 1
 1 1 1 1

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: "Select System info from the Administration panel."