ELO rating

[bal7hazar]

Closes #60

Introduced changes

• Add a method to compute ELO change between two ELO scores
• Introduce a matchmaker contract example very efficient (not a single loop or recursion to match 2 players)

Checklist

• Linked relevant issue
• Updated relevant documentation
• Added relevant tests
• Add a dedicated CI job for new examples
• Performed self-review of the code

[bal7hazar]

@ponderingdemocritus @tarrencev
It will be used as a fondation for a future matchmaking mechanism

[tarrencev]

This is super cool. Do you think it is worth having a match maker module that is easily reusable by games? So people don't end up copy/pasting the example?

[bal7hazar]

This is super cool. Do you think it is worth having a match maker module that is easily reusable by games? So people don't end up copy/pasting the example?

@tarrencev I don't think we can have it generic enough to make it compatible with all games (for instance if you want to do 1v1 or NvN or 1vN, etc.). If we are able to get enough feedbacks after a period of usage, maybe we could consider it again.

In addition, I was also thinking to maybe have a single deployed match marker world to allow people to find an opponent among a selected list of games (worlds), so all the ratings of all subscribed games will be centralised inside a singe Registry (which open the door to Gaming Identity, etc.).
So the match maker will probably come with a MatchMakerGameTrait to implement by games wanted to register.
So for instance you can search for a Pistols or Paved 1v1 game or a zConqueror 1vN, etc. in the same time.
but it will be another version in another PR I think.

[bal7hazar]

@tarrencev @ponderingdemocritus
I have finished the first version I think, tests ongoing @ https://matchmaker-ivory.vercel.app/

[bal7hazar]

Note: PR made to Alexandria keep-starknet-strange/alexandria#296

Edit (2022-04-22): PR has been merged but we will need to have dojo to be compatible with starknet 2.6.3 to be able to add alexandria as a dep.

[bal7hazar]

@tarrencev @ponderingdemocritus are you comfortable to merge it as it is?

I will update these helpers once we are able to support the latest version of Alexandria (currently blocked by dojoengine/dojo#1659).

I think creating a temporary math crate inside origami could be a high risk to encourage developers to add features in it which will be definitely in clash with Alexandria scope, which is something we don't want.

[ponderingdemocritus]

Yeah lets do it