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Rename Tick to Event 

* Define a tick to be an event with no user data.
* Use the term "event log" for now.
** Reserve the word "entry" for hash entries, and "item" for array items.
** Reserve the word "blockchain" for when the event is a block of something.
** Reserve the word "ledger" for when the event is of a particular type,
   such as transactions.
This commit is contained in:
Greg Fitzgerald 2018-02-15 10:13:56 -07:00
parent beb4a643ad
commit a74540470a
3 changed files with 116 additions and 97 deletions
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115
src/event.rs Normal file
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//! The `event` crate provides the foundational data structures for Proof-of-History
/// A Proof-of-History is an ordered log of events in time. Each entry contains three
/// pieces of data. The 'n' field is the number of hashes performed since the previous
/// entry. The 'hash' field is the result of hashing 'hash' from the previous entry 'n'
/// times. The 'data' field is an optional foreign key (a hash) pointing to some arbitrary
/// data that a client is looking to associate with the entry.
///
/// If you divide 'n' by the amount of time it takes to generate a new hash, you
/// get a duration estimate since the last event. Since processing power increases
/// over time, one should expect the duration 'n' represents to decrease proportionally.
/// Though processing power varies across nodes, the network gives priority to the
/// fastest processor. Duration should therefore be estimated by assuming that the hash
/// was generated by the fastest processor at the time the entry was logged.
///
/// When 'data' is None, the event represents a simple "tick", and exists for the
/// sole purpose of improving the performance of event log verification. A tick can
/// be generated in 'n' hashes and verified in 'n' hashes. By logging a hash alongside
/// the tick, each tick and be verified in parallel using the 'hash' of the preceding
/// tick to seed its hashing.
pub struct Event {
pub hash: u64,
pub n: u64,
pub data: Option<u64>,
}
impl Event {
/// Creates an Event from the number of hashes 'n' since the previous event
/// and that resulting 'hash'.
pub fn new(hash: u64, n: u64) -> Self {
let data = None;
Event { hash, n, data }
}
/// Creates an Event from by hashing 'seed' 'n' times.
///
/// ```
/// use loomination::event::Event;
/// assert_eq!(Event::run(0, 1).n, 1)
/// ```
pub fn run(seed: u64, n: u64) -> Self {
use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};
let mut hash = seed;
let mut hasher = DefaultHasher::new();
for _ in 0..n {
hash.hash(&mut hasher);
hash = hasher.finish();
}
Self::new(hash, n)
}
/// Verifies self.hash is the result of hashing a 'seed' 'self.n' times.
///
/// ```
/// use loomination::event::Event;
/// assert!(Event::run(0, 0).verify(0)); // base case
/// assert!(!Event::run(0, 0).verify(1)); // base case, bad
/// assert!(Event::run(0, 1).verify(0)); // inductive case
/// assert!(!Event::run(0, 1).verify(1)); // inductive case, bad
/// ```
pub fn verify(self: &Self, seed: u64) -> bool {
self.hash == Self::run(seed, self.n).hash
}
}
/// Verifies the hashes and counts of a slice of events are all consistent.
///
/// ```
/// use loomination::event::{verify_slice, Event};
/// assert!(verify_slice(&vec![], 0)); // base case
/// assert!(verify_slice(&vec![Event::run(0, 0)], 0)); // singleton case 1
/// assert!(!verify_slice(&vec![Event::run(0, 0)], 1)); // singleton case 2, bad
/// assert!(verify_slice(&vec![Event::run(0, 0), Event::run(0, 0)], 0)); // lazy inductive case
/// assert!(!verify_slice(&vec![Event::run(0, 0), Event::run(1, 0)], 0)); // lazy inductive case, bad
/// ```
pub fn verify_slice(events: &[Event], seed: u64) -> bool {
use rayon::prelude::*;
let genesis = [Event::run(seed, 0)];
let event_pairs = genesis.par_iter().chain(events).zip(events);
event_pairs.all(|(x, x1)| x1.verify(x.hash))
}
/// Verifies the hashes and events serially. Exists only for reference.
pub fn verify_slice_seq(events: &[Event], seed: u64) -> bool {
let genesis = [Event::run(seed, 0)];
let event_pairs = genesis.iter().chain(events).zip(events);
event_pairs.into_iter().all(|(x, x1)| x1.verify(x.hash))
}
/// Create a vector of Ticks of length 'len' from 'seed' hash and 'hashes_since_prev'.
pub fn create_events(seed: u64, hashes_since_prev: u64, len: usize) -> Vec<Event> {
use itertools::unfold;
let mut events = unfold(seed, |state| {
let event = Event::run(*state, hashes_since_prev);
*state = event.hash;
return Some(event);
});
events.by_ref().take(len).collect()
}
#[cfg(all(feature = "unstable", test))]
mod bench {
extern crate test;
use self::test::Bencher;
use event;
#[bench]
fn event_bench(bencher: &mut Bencher) {
let seed = 0;
let events = event::create_events(seed, 100_000, 4);
bencher.iter(|| {
assert!(event::verify_slice(&events, seed));
});
}
}

2
src/lib.rs
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@ -1,4 +1,4 @@
#![cfg_attr(feature = "unstable", feature(test))]
pub mod tick;
pub mod event;
extern crate itertools;
extern crate rayon;

96
src/tick.rs
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@ -1,96 +0,0 @@
//! The `tick` crate provides the foundational data structures for Proof of History
pub struct Tick {
pub hash: u64,
pub n: u64,
pub data: Option<u64>,
}
impl Tick {
/// Creates a Tick from a 'hash' and how many times it hashed the previous entry 'n'.
pub fn new(hash: u64, n: u64) -> Self {
let data = None;
Tick { hash, n, data }
}
/// Creates a Tick from by hashing 'seed' 'n' times.
///
/// ```
/// use loomination::tick::Tick;
/// assert_eq!(Tick::run(0, 1).n, 1)
/// ```
pub fn run(seed: u64, n: u64) -> Self {
use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};
let mut hash = seed;
let mut hasher = DefaultHasher::new();
for _ in 0..n {
hash.hash(&mut hasher);
hash = hasher.finish();
}
Self::new(hash, n)
}
/// Verifies self.hash is the result of hashing a 'seed' 'self.n' times.
///
/// ```
/// use loomination::tick::Tick;
/// assert!(Tick::run(0, 0).verify(0)); // base case
/// assert!(!Tick::run(0, 0).verify(1)); // base case, bad
/// assert!(Tick::run(0, 1).verify(0)); // inductive case
/// assert!(!Tick::run(0, 1).verify(1)); // inductive case, bad
/// ```
pub fn verify(self: &Self, seed: u64) -> bool {
self.hash == Self::run(seed, self.n).hash
}
}
/// Verifies the hashes and counts of a slice of ticks are all consistent.
///
/// ```
/// use loomination::tick::{verify_slice, Tick};
/// assert!(verify_slice(&vec![], 0)); // base case
/// assert!(verify_slice(&vec![Tick::run(0, 0)], 0)); // singleton case 1
/// assert!(!verify_slice(&vec![Tick::run(0, 0)], 1)); // singleton case 2, bad
/// assert!(verify_slice(&vec![Tick::run(0, 0), Tick::run(0, 0)], 0)); // lazy inductive case
/// assert!(!verify_slice(&vec![Tick::run(0, 0), Tick::run(1, 0)], 0)); // lazy inductive case, bad
/// ```
pub fn verify_slice(ticks: &[Tick], seed: u64) -> bool {
use rayon::prelude::*;
let genesis = [Tick::run(seed, 0)];
let tick_pairs = genesis.par_iter().chain(ticks).zip(ticks);
tick_pairs.all(|(x, x1)| x1.verify(x.hash))
}
/// Verifies the hashes and ticks serially. Exists only for reference.
pub fn verify_slice_seq(ticks: &[Tick], seed: u64) -> bool {
let genesis = [Tick::run(seed, 0)];
let tick_pairs = genesis.iter().chain(ticks).zip(ticks);
tick_pairs.into_iter().all(|(x, x1)| x1.verify(x.hash))
}
/// Create a vector of Ticks of length 'len' from 'seed' hash and 'hashes_per_tick'.
pub fn create_ticks(seed: u64, hashes_per_tick: u64, len: usize) -> Vec<Tick> {
use itertools::unfold;
let mut ticks_iter = unfold(seed, |state| {
let tick = Tick::run(*state, hashes_per_tick);
*state = tick.hash;
return Some(tick);
});
ticks_iter.by_ref().take(len).collect()
}
#[cfg(all(feature = "unstable", test))]
mod bench {
extern crate test;
use self::test::Bencher;
use tick;
#[bench]
fn tick_bench(bencher: &mut Bencher) {
let seed = 0;
let ticks = tick::create_ticks(seed, 100_000, 4);
bencher.iter(|| {
assert!(tick::verify_slice(&ticks, seed));
});
}
}