Spaces:
Build error
Build error
File size: 4,716 Bytes
84d2a97 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 |
//! Structures for fast and tread-safe way to check if some points were visited or not
use common::defaults::POOL_KEEP_LIMIT;
use common::types::PointOffsetType;
use parking_lot::RwLock;
/// Visited list handle is an owner of the `VisitedList`, which is returned by `VisitedPool` and returned back to it
#[derive(Debug)]
pub struct VisitedListHandle<'a> {
pool: &'a VisitedPool,
visited_list: VisitedList,
}
/// Visited list reuses same memory to keep track of visited points ids among multiple consequent queries
///
/// It stores the sequence number of last processed operation next to the point ID, which allows to avoid memory allocation
/// and reuse same counter for multiple queries.
#[derive(Debug)]
struct VisitedList {
current_iter: u8,
visit_counters: Vec<u8>,
}
impl Default for VisitedList {
fn default() -> Self {
VisitedList {
current_iter: 1,
visit_counters: vec![],
}
}
}
impl VisitedList {
fn new(num_points: usize) -> Self {
VisitedList {
current_iter: 1,
visit_counters: vec![0; num_points],
}
}
}
impl<'a> Drop for VisitedListHandle<'a> {
fn drop(&mut self) {
self.pool
.return_back(std::mem::take(&mut self.visited_list));
}
}
impl<'a> VisitedListHandle<'a> {
fn new(pool: &'a VisitedPool, data: VisitedList) -> Self {
VisitedListHandle {
pool,
visited_list: data,
}
}
/// Return `true` if visited
pub fn check(&self, point_id: PointOffsetType) -> bool {
self.visited_list
.visit_counters
.get(point_id as usize)
.map_or(false, |x| *x == self.visited_list.current_iter)
}
/// Updates visited list
/// return `true` if point was visited before
pub fn check_and_update_visited(&mut self, point_id: PointOffsetType) -> bool {
let idx = point_id as usize;
if idx >= self.visited_list.visit_counters.len() {
self.visited_list.visit_counters.resize(idx + 1, 0);
}
std::mem::replace(
&mut self.visited_list.visit_counters[idx],
self.visited_list.current_iter,
) == self.visited_list.current_iter
}
pub fn next_iteration(&mut self) {
self.visited_list.current_iter = self.visited_list.current_iter.wrapping_add(1);
if self.visited_list.current_iter == 0 {
self.visited_list.current_iter = 1;
self.visited_list.visit_counters.fill(0);
}
}
fn resize(&mut self, num_points: usize) {
// `self.current_iter` is never 0, so it's safe to use 0 as a default
// value.
self.visited_list.visit_counters.resize(num_points, 0);
}
}
/// Keeps a list of `VisitedList` which could be requested and released from multiple threads
///
/// If there are more requests than lists - creates a new list, but only keeps max defined amount.
#[derive(Debug)]
pub struct VisitedPool {
pool: RwLock<Vec<VisitedList>>,
}
impl VisitedPool {
pub fn new() -> Self {
VisitedPool {
pool: RwLock::new(Vec::with_capacity(*POOL_KEEP_LIMIT)),
}
}
pub fn get(&self, num_points: usize) -> VisitedListHandle {
// If there are more concurrent requests, a new temporary list is created dynamically.
// This limit is implemented to prevent memory leakage.
match self.pool.write().pop() {
None => VisitedListHandle::new(self, VisitedList::new(num_points)),
Some(data) => {
let mut visited_list = VisitedListHandle::new(self, data);
visited_list.resize(num_points);
visited_list.next_iteration();
visited_list
}
}
}
fn return_back(&self, data: VisitedList) {
let mut pool = self.pool.write();
if pool.len() < *POOL_KEEP_LIMIT {
pool.push(data);
}
}
}
impl Default for VisitedPool {
fn default() -> Self {
VisitedPool::new()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_visited_list() {
let pool = VisitedPool::new();
let mut visited_list = pool.get(10);
for _ in 0..2 {
assert!(!visited_list.check(0));
assert!(!visited_list.check_and_update_visited(0));
assert!(visited_list.check(0));
assert!(visited_list.check_and_update_visited(0));
assert!(visited_list.check(0));
for _ in 0..(u8::MAX as usize * 2 + 10) {
visited_list.next_iteration();
assert!(!visited_list.check(0));
}
}
}
}
|