From Alpha Go to Alpha Zero

1. From Alpha Go to
Alpha Zero
Vaas
May 2018

2. Juantomás García
• Data Solutions Manager @ OpenSistemas
• GDE (Google Developer Expert) for cloud
Others
• Co-Author of the first Spanish free software book “La Pastilla
Roja”
• President of Hispalinux (Spanish Linux User Group)
• Organizer of the Machine Learning Spain and GDG Cloud Madrid.
Who I am

3. • People interested in Machine Learning
• Wants to know more about what’s is Alpha Go
• With a good technical background.
Who are the Audience

4. • I love Machine Learning.
• There are a lot of takeaways from this project.
• I wish to divulge it
Why I did this presentation

5. • Alpha Go: the epic project
• AlphaGo Zero: re-evolution version
• Alpha Zero: Looking for general solutions
• DIY: Alpha Zero Connect 4
• Takeaways
Outline

6. A brief introduction
• Deep Blue was about brute force
• They were emulating how humans play chess

7. A brief introduction
• A very huge Search Space
Chess -> Opening 20 possible moves
Go -> Opening 361 possible moves

8. Alpha Go Main Concepts
• Policy Neural Network
“To decide which are the most sensible moves in
a particular board position”.

9. Alpha Go Main Concepts
• Value Neural Network
“How great is a particular board arrangements”.
“How likely you are to win the game with this
position”.

10. Alpha Go Main Concepts

11. Alpha Go First Approach: SL
• Just train both networks using human games.
• Just old and ordinary supervised learning.
• With this: AlphaGo just play with like a weak
human.
• It like the approach of deep blue: just emulating
human chess players

12. Alpha Go First Approach: SL

13. Alpha Go Second Approach: RL
• Improve SL version starting playing again itself.
• With Reinforcement Learning is able to play well
against state of the art go playing programs
• These programs are using MCTS

14. Alpha Go Second Approach: RL

15. Alpha Go Second Approach: RL
• It is not 2 NN vs Monte Carlo Tree Search
• Is a better MCTS thanks to the NNs.

16. Alpha Go Second Approach: RL
• Optimal Value Function V*(s)
“Determine the outcome of the game from every
board position (s is the state)”.
Brute force solution is impossible:
Chess: 35 ** 80
Go: 250 ** 150

17. Alpha Go Second Approach: RL
• Two solutions for reduce the effective search
space:
Truncate the tree subtree search: V(s) like V*(s)
Reducing the breadth of the search with the
policy: P(a|s)
We MCTS rollout the moves choose by the policy
function and evaluate with the optimal value
function.

18. AlphaGo: The Match

19. AlphaGo Zero: Re-Evolution version
• Just trained with Reinforcement Learning
• Choose the less out different moves: u(s,a)
• Just one neural network for policy and value.
• Every time a search is done the neural network is
retrained.

20. AlphaGo Zero: Re-Evolution version
• Human games was noisy and not reliable.
• Don’t use rollouts for predict who will win.

21. AlphaGo Zero: Re-Evolution version

22. AlphaGo Zero: Re-Evolution version

23. Alpha Zero: New Challenges
AlphaGo Zero VS AlphaZero:
• Binary outcome (win / loss) × expected outcome
(including
• 3 draws or potentially other outcomes)
• Board positions transformed before passing to neural
networks (by randomly selected rotation or redirection) × no
data augmentation
• Games generated by the best player from previous iterations
(margin of 55 %) × continual update using the latest
parameters (without the evaluation and selection steps)
• Hyper-parameters tuned by Bayesian optimisation × reused
the same hyper-parameters without game-specific tuning

24. Alpha Zero

25. Alpha Zero: DYI
https://medium.com/applied-data-science/how-to-build-your-own-alphazero-ai-using-python-and-keras-7f664945c188

26. Takeaways
RL is more than Atari Games and GO

27. Takeaways
AI discovery new ways to play.
Think about new projects like proteins fold.

28. Takeaways
We’re living awesome times.
Sharing AI papers, tools, models, etc. More
than any time before.

29. Takeaways
As Ms Fei Fei said: “It’s about democratizing AI”

30. Takeaways
Watch this Documentary Film about Alpha Go:

31. Thank You