Lighthouse: Update shuffle() as per latest spec update

[paulhauner]

Description

The shuffle() function in the Eth 2.0 spec has changed. We need to update our function.

Resources:

• Our shuffle crate: https://github.com/sigp/lighthouse/tree/master/beacon_chain/utils/shuffling
• Spec update PR: https://github.com/ethereum/eth2.0-specs/pull/65

Present Behaviour

RAND_MAX is presently set to 2**24.

Expected Behaviour

RAND_MAX should be 2**24 - 1.

Steps to resolve

1. Change RAND_MAX
2. Use sigp/shuffling_sandbox to generate some test vectors. There's only 1 test vector in there now, we should throw in multiple (make sure you use different list sizes).

Hint: shuffling_sandbox cmd: $ python sandbox.py print --list-size LIST_SIZE

[gitcoinbot]

Issue Status: 1. Open 2. Started 3. Submitted 4. Done

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[gitcoinbot]

Issue Status: 1. Open 2. Started 3. Submitted 4. Done

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__Work has been started__.

These users each claimed they can complete the work by 7 months, 1 week from now.
Please review their action plans below:

1) pinkiebell has been approved to start work.

I can resolve the issue this weekend.
It will also be nice to digging with rust again :)

Learn more on the Gitcoin Issue Details page.

2) pvgupta24 has applied to start work _(Funders only: approve worker | reject worker)_.

Hello everyone, I believe I can resolve this issue and start my contribution to this project :)

Here's my action plan for the same :

• Update the RAND_MAX value to be used
• Generate test vectors of different sizes to cover corner cases and check.

Learn more on the Gitcoin Issue Details page.

3) shamardy has applied to start work _(Funders only: approve worker | reject worker)_.

I would like to work on this issue. I worked on multiple rust and Ethereum issues before in parity-ethereum client and parity substrate.

Learn more on the Gitcoin Issue Details page.

4) toya999 has applied to start work _(Funders only: approve worker | reject worker)_.

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Learn more on the Gitcoin Issue Details page.

[pinkiebell]

I wasn't sure if this is just a approval-only bounty by accident or not because of the PR @6ug opened.
However, couldn't withstand to play with Rust this weekend, so I thought I play with Rust and solving this issue along the way 👍

[paulhauner]

I'm new to this bounty thing, so please bear with me whilst I figure it out.

I can see that @pinkiebell was the first to apply and has already submitted some great work at #57, so it seems fair to me that they receive the grant.

I will ask the person who funded the issue (not me) to approve the funding. Thanks to all who applied!

[6ug]

I can see that @pinkiebell was the first to apply and has already submitted some great work at #57, so it seems fair to me that they receive the grant.

I was little late while applying and work, I agree with decision and @pinkiebell should get grant, closing my PR, good job buddy! :100:

[pinkiebell]

@paulhauner @6ug
No problem, I normally wait for a comment but because it was already weekend and assuming 'first dibs', I just dived into the codebase 😄 .

[mkosowsk]

@pinkiebell you have been approved to start work (now that you have finished it 😂). Please submit your work here and I will pay out ASAP.