https://github.com/cocol-project/probfin
Probabilistic Finality for Crystal
https://github.com/cocol-project/probfin
blockchain cocol crystal crystal-lang crystal-language dag finality probabilistic-finality topsort
Last synced: 2 months ago
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Probabilistic Finality for Crystal
- Host: GitHub
- URL: https://github.com/cocol-project/probfin
- Owner: cocol-project
- License: mpl-2.0
- Created: 2019-09-17T13:46:07.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2020-03-04T14:06:38.000Z (over 5 years ago)
- Last Synced: 2024-10-06T03:06:57.910Z (8 months ago)
- Topics: blockchain, cocol, crystal, crystal-lang, crystal-language, dag, finality, probabilistic-finality, topsort
- Language: Crystal
- Homepage: https://cocol-project.github.io/probfin/
- Size: 339 KB
- Stars: 3
- Watchers: 2
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Cocol Probabilistic Finality
Based on DAGs, it manages chains, sidechains and orphans. Given a threshold of
confirmations it returns the next finalized block.
## Installation
1. Add the dependency to your `shard.yml`:
``` yaml
dependencies:
probfin:
github: cocol-project/probfin
```
2. Run `shards install`
## Usage
``` crystal
require "probfin"
```
``` crystal
# (a0)---aa---ba---ca---da---ea---fa
# \ \
# bb cb---cc
# add blocks (aa, a0 should be block hashes)
ProbFin.push(block: "aa", parent: "a0")
ProbFin.push(block: "ba", parent: "aa")
ProbFin.push(block: "bb", parent: "ba")
...
ProbFin.finalize from: "aa",
chain_length_threshold: 5, # 5 confirmations (fa being the 5th)
tip_diff_threshold: 0 # how many more confirmations should it have compared to sidechains
# => ba
```
## How ProbFin works
The data structure above resembles a Directed Acyclic Graph (DAG) and fortunately DAGs allow for an easy way to find the longest chain. This is an important part of achieving probabilistic finality.
A DAG is made up of nodes (also called vertices) and edges. An edge represents a link between 2 vertices (e.g. `3000.1->3001.1`). We can and should traverse a DAG to find out more about its structure, like how far away is vertex `3005.1` from vertex `3000.1`
Additionally a DAG has some unique properties. Find out more about it [here](https://www.youtube.com/watch?v=TXkDpqjDMHA)
**2. How to find the longest chain**
If we look again at the example above, it becomes apparent that `3005.1` is the tip of the longest chain. But how can we find it out programmatically?
We are going to use [Depth First Search](https://www.youtube.com/watch?v=7fujbpJ0LB4) to traverse the graph and mark every vertex with its distance from the starting vertex.
We start at `3000.1` and give it a distance of `0`. Now we traverse through all vertices and give each a distance of `parent distance + 1`. So `3001.1` has a `parent distance` of `0` and `+1` gives a distance of `1`.
## Contributing
1. Fork it ()
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request
## Contributors
- [cserb](https://github.com/cserb) - creator and maintainer