Computer Reversi, Part 1.5: The Thor database (Othello tournament files)

As part of my research into Reversi, I looked for an archive of games. The only substantial one I found is called the Thor Database. It's an archive of Othello games by French archivers. They have archived are over 100,000 games. You can download the game databases here.

My initial motivation for finding an archive was to have a easy way to unit test my code to ensure it implemented the Reversi rules correctly. If the game engine could play through 100,000 games and calculate the final score, that's a good indication that the rules have been implemented correctly. An archive can also be used for book openings. I have another idea for the archive too, which I will hopefully reveal soon.

My Reversi source code has a Thor project with a bunch of methods and classes for extracting the data for whatever nefarious needs you may have. I don't think there is any code in C# on the net for this, so maybe one day it'll be helpful for someone. Maybe. (Probably not.)

The file format documentation is challenging to understand because it is written in French. I have translated (thanks to Nuz and google translate) the core elements of the document in the section below. The aspects I found challenging were:

• Interpreting the meaning of the black player's score (I needed to calculate the score as the final check to ensure my rules were working)
• Interpreting the way they recorded the individual plays
• Converting elements of a byte-array to a 16-bit integer. (The data are stored as little-endian. One way: BitConverter.ToInt16(new [] { thorArray[i], thorArray[i + 1] }, 0).)

To calculate the Black Score:

• Get sum of black pieces and the sum of white pieces;
• Whoever has the most pieces wins;
• The winner adds to the sum the number of empty squares;

E.g., Black has 44 pieces, White has 8 pieces; Black's score is 56. Or, Black has 13 pieces, White has 35; Black's score is 13. In the case of a draw, Black's score is 32 (as the empty squares are shared between Black and White, 32 is the only possible score for a draw). I still haven't figured out what it means for Black's score when the game ends before neither player can play a piece. The score seems inconsistent. This only occurs in 406 of 107,473 games. (Not a big deal.)

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The data, such as Word and Longint, are stored in Intel format, ie the lowest byte first. There is a game file for every year. Games are stored in any order, but normally grouped by tournament.

Database header fields
All files in the database Wthor have a header of 16 bytes, followed by a number of game records all having the same size. The header consists of the following fields:

• Century file was created
• Year file was created
• Month file was created
• Date file was created
• Number of records N1
• Number of records N2
• Year of game
• Parameter P1: size game board
• P2 parameter: type of games
• Parameter P3: depth
• X1 (reserved)

Game fields

• Tournament Number
• Number of Black player
• Number of White player
• Number of black pieces (true score)
• Theoretical score
• Move list 

The plays are stored in chronological order. Row number (1-8) and column (A-H) can be derived from the following operation: column + (10 * row). E.g., a1 = 11, h1 = 18, a8 = 81, h8 = 88.

Tournament file

Each record (26 bytes) is an array of characters terminated by a binary zero. The effective length is 25 characters. There is a 16 byte header for this file. 

Player file

Each record (20 bytes) is an array of characters terminated by a binary zero. The effective length is 19 characters. There is a 16 byte header for this file.

JavaScript - Accessibility and Useability

There has been talk at work about having to provide non-JavaScript alternatives for any of our web-pages that use JavaScript. A few people were suspicoius of this idea and given that we're using MVC3, they were finding it very difficult to implement functionality without JavaScript. Below is the document I created after reading compliance info on the net. You can also download as a Word doc.

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JavaScript - Accessibility and Useability on the Web

Below are the relevant sections of documents concerning JavaScript and its impact on website accessibility and useability. I have checked documents relating to accessibility compliance under Australian law, compliance for US law and more general accessibility sites. In the conclusion, I explain a public website’s responsibilities regarding JavaScript and accessibility/useability.

Disability Discrimination Act Advisory Notes

http://www.hreoc.gov.au/disability_rights/standards/www_3/www_3.html

It is important for developers to understand that in many cases the accessibility of a particular technology will be determined by how it is used. For example, it is widely considered that JavaScript can be implemented so as to be accessible. However, JavaScript can also be used in ways that are inaccessible, particularly if full keyboard support is not provided.
Ten Common Web Accessibility Failures

1. Failure to include appropriate text descriptions (such as “alt-text” labels) for images;

2. Failure to provide accessible alternatives when using a visual CAPTCHA;

3. Failure to use technologies (such as Flash and JavaScript) in ways that are accessible;

4. Failure to use HTML features appropriately to indicate content structure such as the hierarchy of headings;

5. Failure to explicitly associate form input controls with their labels;

6. Failure to ensure sufficient difference between foreground (text) colour and background colour;

7. Failure to identify data tables with Summary or Caption, and failure to mark-up data tables correctly;

8. Failure to provide a way for users to disable content such as advertisements from flashing rapidly (rapidly-flashing content may cause seizures in susceptible individuals), and failure to provide a way for users to stop a page from auto-refreshing;

9. Failure to ensure that web pages can be used from the keyboard (that is, without the mouse);

10. Failure to alert the user to changes on a web page that are triggered automatically when selecting items from a dropdown menu.

How to Meet WCAG 2.0

http://www.w3.org/WAI/WCAG20/quickref/

1.1 Text Alternatives: Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.

1.2 Time-based Media: Provide alternatives for time-based media.

1.3 Adaptable: Create content that can be presented in different ways (for example simpler layout) without losing information or structure.

1.4 Distinguishable: Make it easier for users to see and hear content including separating foreground from background.

2.1 Keyboard Accessible: Make all functionality available from a keyboard.

2.2 Enough Time: Provide users enough time to read and use content.

2.3 Seizures: Do not design content in a way that is known to cause seizures.

2.4 Navigable: Provide ways to help users navigate, find content, and determine where they are.

3.1 Readable: Make text content readable and understandable.

3.2 Predictable: Make Web pages appear and operate in predictable ways.

3.3 Input Assistance: Help users avoid and correct mistakes.

4.1 Compatible: Maximize compatibility with current and future user agents, including assistive technologies.

(No specific mention of JavaScript.)

Migrating from WCAG 1.0 to WCAG 2.0

http://wipa.org.au/papers/wcag-migration.htm

Ensure that pages are usable when scripts, applets etc are turned off or not supported. If this is not possible, provide equivalent information on an alternative accessible page. [Priority 1]

NO MATCHING WCAG 2.0 S.C. Issue is addressed as part of "Conformance requirements".

NB: WCAG 2.0 does not require alternative to be always provided for JavaScript etc. But nominated "accessibility supported technologies" must be used in a way that is accessible. Conformance requirement 4: Only accessibility supported technologies are relied on to satisfy the success criteria. AND Conformance requirement 5: If technologies that are not accessibility supported are used, they do not stop users accessing the rest of the page.

Accessible Rich Internet Applications (WAI-ARIA) 1.0

http://www.w3.org/WAI/PF/aria/introduction#intro_ria_accessibility

New technologies often overlook semantics required for accessibility, and new authoring practices often misuse the intended semantics of those technologies. Elements that have one defined meaning in the language are used with a different meaning intended to be understood by the user.

For example, web application developers create collapsible tree widgets in HTML using CSS and JavaScript even though HTML has no semantic tree element. To a non-disabled user, it may look and act like a collapsible tree widget, but without appropriate semantics, the tree widget may not be perceivable to, or operable by, a person with a disability because assistive technologies may not recognize the role.

Screen readers vs JavaScript

http://webaim.org/projects/screenreadersurvey3/#javascript

JavaScript Enabled = 98.4%, Disabled = 1.6%

10.4% of respondents to the October 2009 survey indicated that they have JavaScript disabled in their web browser. As respondents submitted responses to this survey we detected the presence of JavaScript. We found that very few respondents had it disabled or unavailable in their web browser. Of the 19 respondents with JavaScript disabled, 12 were using Firefox (presumably with the NoScript add-on enabled) and 5 were using Lynx with Linux.

Creating Accessible JavaScript

http://webaim.org/techniques/javascript/

Making JavaScript accessible involves looking at the following issues. Each of these will be discussed in the next lessons.

·         When using event handlers, use only those that are device independent (e.g., do not require the use of the mouse only).

·         Content and functionality that is provided through scripting must be made accessible to assistive technologies.

·         Web pages that utilize scripting must be fully navigable using a keyboard.

·         JavaScript should not modify or override normal browser functionality in a way that may cause confusion.

·         When JavaScript cannot be made natively accessible, an accessible alternative must be provided.

Accessible forms: Guidelines, examples and accessible JavaScript tricks.

http://www.websemantics.co.uk/tutorials/accessible_forms/

So what will you find here?

·         A list of form guidelines based on current and on-going research into accessibility, usability and web standards.

·         Simple examples of accessible forms including: a login form, a search form and a contact form.

·         Examples and help on each form element.

·         Styling forms with CSS.

·         Using accessible inline JavaScript to aide form functionality.

·         Using accessible JavaScript with the DOM to aide form functionality.

·         A comprehensive list of external form related articles and resources.

Conclusion

W3C, Australian law and US law either make no comment on JavaScript or state that JavaScript is acceptable as long as accessibility is maintained.

WCAG 1.0 required that non-JavaScript alternatives were required. WCAG 2.0 does not have this requirement. In compliance with WCAG 2.0, we are permitted to implement pages that would not be useable without JavaScript so long as they remain accessible.

The guidelines at http://webaim.org/techniques/javascript/ and http://www.websemantics.co.uk/tutorials/accessible_forms/ can assist in determining how to ensure the use of JavaScript on a website is accessible.

Computer Reversi, Part 1 (Or how I learned to stop worrying and love the bits)

After noughts and crosses I thought I’d try Reversi (Othello). Reversi has simpler rules than chess but remains complex enough that it hasn’t been mathematically solved, yet.

I thought I’d find a wealth of information on the net about how to program a Reversi game. However, there wasn’t all that much out there. I found some helpful blog entries at Red Alt Blog. I used that as my starting point.

The best resource for understanding how to program Reversi is at the chess programming wiki. They have an Othello page as well as pages that helped me do a bitboard version of Reversi, with move generation and resolution (dumb7fill), population count (i.e., number of bits on the board) and board serialisation (using bitscans). I'm hoping it'll also be helpful for position evaluation later on.

The tasks needed to code a Reversi computer game with a learning computer opponent are

1. Game state representation
2. Move generation
3. Move resolution
4. Determine game over and winner
5. Graphic User Interface
6. Save/load and undo/redo moves
7. Position evaluation (i.e., fitness/objective function)
8. Depth-first search algorithm (e.g., mini-max or nega-scout)
9. Book/database based analysis (e.g., opening book, transposition tables) 
10. Mathematical optimisation (e.g., simulated annealing or genetic algorithm)

This blog entry addresses steps 1-6, providing source code for a Unity implementation of Othello. The game logic is written as C# and compiles as mono inside Unity. I assume knowledge of:

• C#
• Unity 3D
• Reversi rules

The following sections describe some interesting parts of the source code, relating with the first six steps outlined above.

Reading the source code

The entry point for the application (the Main method) is the Start method of the GameBehaviour.cs file. This file is attached to the main camera in Unity. The GameBehaviour.cs file creates the board and pieces as 3D objects and hosts an instance of GameManager (see below). It also manages the UI controls to save/load games, undo/redo moves, setup the human/computer players, start a new game, etc.

The files that do all the real work are:

• GameBehaviou.cs
• GameManager.cs
• GameState.cs
• BitBoardHelper.cs
• Play.cs

There are source files, 64-bit Windows binaries and Mac OSX binaries. There are two solutions files contained in the source files. The one named with VS2010 is the one you should open in Visual Studio. It contains a test project and a preliminary attempt at reading the Thor database format. But that will be for another post. You can load the project in Unity via the "Reversi.unity" in the Assets sub-folder.

GameManager

The GameManager class does the work-a-day tasks of the game. Tasks such as:

• Save/load
• Undo/redo
• Tells you whose turn it is
• Tracks the list of plays
• Tracks the turn number

GameState

My GameState class handles most of the game rules of a Reversi game. You pass it two unsigned 64-bit integers (ulong in C#). These numbers are a bitboard representation of the game. The first number represents the current player's pieces. The second number represents the opponent's pieces. E.g., the starting position for black is represented as 0000000000000000000000000001000000001000000000000000000000000000 in binary. When you lay out those zeros and ones on an Reversi board, you get:

Why represent the pieces like this? Bitboards appear to have advantages over other board representations. They appealed to me because I often feel withdrawn from the goings on of the computer. Bitboards were a chance to get in closer to the CPU and play around with individual bits.

One interesting aspect of the GameState class is that it is temporally agnostic. It doesn't know what turn of the game it is. It doesn't even know whose colour is to play next. All it cares about is that it is someone's turn and it figures out where they can play and what happens to the board once they do. I like the simplicity of not needing to deal with time.

The GameState class will tell you if the game is over and whether the current player has won.

BitBoardHelper

I created a BitBoardHelper class to add some extension methods to my ulong bitboards. These methods allow me to count the number of bits, find the indices of the bits and find the unoccupied bits of any two bitboards. I'll probably expand this class when I work on the computer opponent.

For finding the indices (bitboard serialisation) I used the De Bruijn method to do the bitscanning. For the bit count (population count) I used the SWAR Popcount routine.

Play

There is a Play class in the project that will find all the valid moves for the current player and also resolve a chosen move (i.e., flip of the pieces that need to flipped once a piece has been played). The basic idea is to focus one direction (cardinal or ordinal) at a time, scanning 8 locations in parallel. Red Alt explains it well (see under the bitboard heading). Once I could detect where a player could place a piece, I used a very similar method to resolve that move. This class is called by the GameState class and is only different to the BitBoardHelper class in that it has specifically Reversi functionality.

Graphic User Interface

The GUI uses the Unity 3D graphics engine. Much of the code that I use in the Reversi project is a simpler version to what is found in a previous article on Unity and path-finding. Unity displays the board and captures user input.

Save/load games and undo/redo moves

Save/load and undo/redo are interrelated. To do them, I need to keep track of the moves made by the players. If I do that, I can:

• Save: Write the move list to the hard drive.
• Load: Read the move list from the hard drive, start a new game, apply move list - one move at a time - until the last move is applied.
• Undo: Start a new game, apply move list until the desired turn (similar to load).
• Redo: Identical to undo.

Part 2

In Part 2, I intend to cover the aspects of creating a computer opponent for Reversi. The primary goal is to be able create an opponent that can beat me in a game. (Not a highly goal.) Hopefully, I'll be able to have it beat all but the best Reversi players.

Google Translate

Google Translate works quite well. Occasionally it does some weird things. For instance, it translates (from Spanish)

No me acuerdo bien cómo me aparecìa.

to

I do not remember exactly how I appeared.

That is exactly what I'd expect it to say. However, when I change it by one word, 

No me acuerdo muy bien cómo me aparecìa. 

I get

I remember very well how I appeared.

rather than

I do not remember very well how I appeared.

If you change the initial verb to a synonym, it's correct. I.e.,

No recuerdo muy bien cómo me aparecìa.

becomes

I do not remember very well how I appeared.

I assume it's an error in Google Translate rather than me missing the subtleties of the Spanish language. Yet it seems like such a weird thing to get wrong. I'd really like to get into natural language parsing one day. Maybe then I'd discover the answer.

Paragliding Tasmania

I and four other paragliding pilots went to the South West Tasmania in December 2011 to fly. On the first day we looked at the Sentinels then flew 12 Trees (5min flight, unfortunately). On the second day we did a couple of good flights off Mt Elisa. We had excellent conditions, mostly blue skies with a little bit of cumulus. Wind was light and nicely flowing up the ridges. Launching was relatively easy. Some of the thermals were strong but the cores were tight and difficult to exploit for beginners.

Flying with Lake Pedder in the background was amazing. Only Klaus (our Austrian import) had a good flight. He flew down to the last ridge then made his way up, above launch, above Mt Elisa, then eventually above Mt Anne. It was really impressive stuff. The rest of us merely delayed our descents. Nevertheless, it was incredibly good fun.

Photos from the trip can be found here.

After the South West, Mark and I tried to fly Winton (the most accessible site out of Hobart). Unfortunately the wind was high and we didn't have the confidence/experience to give it a go. It was good to watch the locals fly the site, however. Hopefully next time we'll get to fly there.

Editing IE settings in the registry via C#

We have a weird setup at work where our Internet Explorer LAN configuration settings are periodically reset by people who manage the network. This brings IE and TFS to a crawl for the programmers. It doesn't seem to happen to everyone all at once or at a designated time. It can take a few minutes to realise what is going on as there are a number of issues that show similar behaviour. For new programmers, this is especially frustrating because they're not aware of this strange policy.

To the Windows registry Batman! I haven't played with this thing in years. I never really understood it very well. "Hierarchical database? All these weird names? Huh? What's going on?!" Seems so simple now.

Editing the registry in the .NET environment is easy. See here.
Finding how to change LAN proxy configuration settings took a little longer to find. Explained here.
Proxy exceptions? See here.

With the app working, all that is left to do is set the script to run every 15mins on the programmers' computers, and we're done.

Code looks like:

var key = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Internet Settings\Connections", true);
 
if (key == null)
  throw new NullReferenceException("Registry SubKey not found.");
 
const string defaultConnectionSettings = "DefaultConnectionSettings";
var defaultConnectionSettingsValue = (byte[])key.GetValue(defaultConnectionSettings);
 
defaultConnectionSettingsValue[8] = 1;
key.SetValue(defaultConnectionSettings, defaultConnectionSettingsValue, RegistryValueKind.Binary);

Code generation in C#

I wrote my first code generator on the weekend. The real work - generating the C# class files - was trivial. Getting the generator into a state so that it could be easily used was more difficult.

There are a few ways you could do code generation in .NET. I explored:

• Console application that churns out ".cs" files
• Custom Tool for Visual Studio
• T4 Templates

I went with T4 Templates. They were a little obscure at first but provided the easiest entry point into using the code generator. You just build-up your source file and then right-click and select "Run Custom Tool" on the .tt file to generate the code.

I encounted a few issues when trying to write my template. They were:

• Extension methods can't be embedded into a T4 Template. There is a workaround. I ended up converting my extension methods into normal methods (I only had two).
• Accessing your assemblies is difficult in Visual Studio 2010. It has been explained very well. I managed to access my assemblies by writing something like <#@ assembly name="$(SolutionDir)..\DomainEntities\bin\Debug\Cpa.DomainEntities.dll" #>

The example T4 Templates I found on the Internet were a little more complex than what I wanted. (Examples should be as simple as possible.) I wanted to load a source file into memory and generate class files from that. Download my example template if you want something similar. It loads in a CSV file that has two columns (first column is the name of the class, second column the name of the property) and generates some puesdo-code of what the class files will eventually look like. I used this as my base template, then expanded it to create proper C# class files.