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use {
itertools::Itertools,
rand::distributions::{Distribution, WeightedIndex},
rand_chacha::{rand_core::SeedableRng, ChaChaRng},
solana_sdk::pubkey::Pubkey,
std::{collections::HashMap, convert::identity, ops::Index, sync::Arc},
};
#[derive(Clone, Debug)]
pub struct FixedSchedule {
pub leader_schedule: Arc<LeaderSchedule>,
pub start_epoch: u64,
}
#[derive(Debug, Default, PartialEq)]
pub struct LeaderSchedule {
slot_leaders: Vec<Pubkey>,
index: HashMap<Pubkey, Arc<Vec<usize>>>,
}
impl LeaderSchedule {
pub fn new(ids_and_stakes: &[(Pubkey, u64)], seed: [u8; 32], len: u64, repeat: u64) -> Self {
let (ids, stakes): (Vec<_>, Vec<_>) = ids_and_stakes.iter().cloned().unzip();
let rng = &mut ChaChaRng::from_seed(seed);
let weighted_index = WeightedIndex::new(stakes).unwrap();
let mut current_node = Pubkey::default();
let slot_leaders = (0..len)
.map(|i| {
if i % repeat == 0 {
current_node = ids[weighted_index.sample(rng)];
}
current_node
})
.collect();
Self::new_from_schedule(slot_leaders)
}
pub fn new_from_schedule(slot_leaders: Vec<Pubkey>) -> Self {
let index = slot_leaders
.iter()
.enumerate()
.map(|(i, pk)| (*pk, i))
.into_group_map()
.into_iter()
.map(|(k, v)| (k, Arc::new(v)))
.collect();
Self {
slot_leaders,
index,
}
}
pub fn get_slot_leaders(&self) -> &[Pubkey] {
&self.slot_leaders
}
pub fn num_slots(&self) -> usize {
self.slot_leaders.len()
}
pub(crate) fn get_indices(
&self,
pubkey: &Pubkey,
offset: usize,
) -> impl Iterator<Item = usize> {
let index = self.index.get(pubkey).cloned().unwrap_or_default();
let num_slots = self.slot_leaders.len();
let size = index.len();
#[allow(clippy::reversed_empty_ranges)]
let range = if index.is_empty() {
1..=0
} else {
let offset = index
.binary_search(&(offset % num_slots))
.unwrap_or_else(identity)
+ offset / num_slots * size;
offset..=usize::MAX
};
range.map(move |k| index[k % size] + k / size * num_slots)
}
}
impl Index<u64> for LeaderSchedule {
type Output = Pubkey;
fn index(&self, index: u64) -> &Pubkey {
let index = index as usize;
&self.slot_leaders[index % self.slot_leaders.len()]
}
}
#[cfg(test)]
mod tests {
use {super::*, rand::Rng, std::iter::repeat_with};
#[test]
fn test_leader_schedule_index() {
let pubkey0 = solana_sdk::pubkey::new_rand();
let pubkey1 = solana_sdk::pubkey::new_rand();
let leader_schedule = LeaderSchedule::new_from_schedule(vec![pubkey0, pubkey1]);
assert_eq!(leader_schedule[0], pubkey0);
assert_eq!(leader_schedule[1], pubkey1);
assert_eq!(leader_schedule[2], pubkey0);
}
#[test]
fn test_leader_schedule_basic() {
let num_keys = 10;
let stakes: Vec<_> = (0..num_keys)
.map(|i| (solana_sdk::pubkey::new_rand(), i))
.collect();
let seed = solana_sdk::pubkey::new_rand();
let mut seed_bytes = [0u8; 32];
seed_bytes.copy_from_slice(seed.as_ref());
let len = num_keys * 10;
let leader_schedule = LeaderSchedule::new(&stakes, seed_bytes, len, 1);
let leader_schedule2 = LeaderSchedule::new(&stakes, seed_bytes, len, 1);
assert_eq!(leader_schedule.slot_leaders.len() as u64, len);
assert_eq!(leader_schedule, leader_schedule2);
}
#[test]
fn test_repeated_leader_schedule() {
let num_keys = 10;
let stakes: Vec<_> = (0..num_keys)
.map(|i| (solana_sdk::pubkey::new_rand(), i))
.collect();
let seed = solana_sdk::pubkey::new_rand();
let mut seed_bytes = [0u8; 32];
seed_bytes.copy_from_slice(seed.as_ref());
let len = num_keys * 10;
let repeat = 8;
let leader_schedule = LeaderSchedule::new(&stakes, seed_bytes, len, repeat);
assert_eq!(leader_schedule.slot_leaders.len() as u64, len);
let mut leader_node = Pubkey::default();
for (i, node) in leader_schedule.slot_leaders.iter().enumerate() {
if i % repeat as usize == 0 {
leader_node = *node;
} else {
assert_eq!(leader_node, *node);
}
}
}
#[test]
fn test_repeated_leader_schedule_specific() {
let alice_pubkey = solana_sdk::pubkey::new_rand();
let bob_pubkey = solana_sdk::pubkey::new_rand();
let stakes = vec![(alice_pubkey, 2), (bob_pubkey, 1)];
let seed = Pubkey::default();
let mut seed_bytes = [0u8; 32];
seed_bytes.copy_from_slice(seed.as_ref());
let len = 8;
let leaders1 = LeaderSchedule::new(&stakes, seed_bytes, len, 1).slot_leaders;
let leaders2 = LeaderSchedule::new(&stakes, seed_bytes, len, 2).slot_leaders;
assert_eq!(leaders1.len(), leaders2.len());
let leaders1_expected = vec![
alice_pubkey,
alice_pubkey,
alice_pubkey,
bob_pubkey,
alice_pubkey,
alice_pubkey,
alice_pubkey,
alice_pubkey,
];
let leaders2_expected = vec![
alice_pubkey,
alice_pubkey,
alice_pubkey,
alice_pubkey,
alice_pubkey,
alice_pubkey,
bob_pubkey,
bob_pubkey,
];
assert_eq!(leaders1, leaders1_expected);
assert_eq!(leaders2, leaders2_expected);
}
#[test]
fn test_get_indices() {
const NUM_SLOTS: usize = 97;
let mut rng = rand::thread_rng();
let pubkeys: Vec<_> = repeat_with(Pubkey::new_unique).take(4).collect();
let schedule: Vec<_> = repeat_with(|| pubkeys[rng.gen_range(0, 3)])
.take(19)
.collect();
let schedule = LeaderSchedule::new_from_schedule(schedule);
let leaders = (0..NUM_SLOTS)
.map(|i| (schedule[i as u64], i))
.into_group_map();
for pubkey in &pubkeys {
let index = leaders.get(pubkey).cloned().unwrap_or_default();
for offset in 0..NUM_SLOTS {
let schedule: Vec<_> = schedule
.get_indices(pubkey, offset)
.take_while(|s| *s < NUM_SLOTS)
.collect();
let index: Vec<_> = index.iter().copied().skip_while(|s| *s < offset).collect();
assert_eq!(schedule, index);
}
}
}
}