sketches_ddsketch/
store.rs#[cfg(feature = "use_serde")]
use serde::{Deserialize, Serialize};
const CHUNK_SIZE: i32 = 128;
fn div_ceil(dividend: i32, divisor: i32) -> i32 {
(dividend + divisor - 1) / divisor
}
#[derive(Clone, Debug)]
#[cfg_attr(feature = "use_serde", derive(Serialize, Deserialize))]
pub struct Store {
bins: Vec<u64>,
count: u64,
min_key: i32,
max_key: i32,
offset: i32,
bin_limit: usize,
is_collapsed: bool,
}
impl Store {
pub fn new(bin_limit: usize) -> Self {
Store {
bins: Vec::new(),
count: 0,
min_key: i32::MAX,
max_key: i32::MIN,
offset: 0,
bin_limit,
is_collapsed: false,
}
}
pub fn length(&self) -> i32 {
self.bins.len() as i32
}
pub fn is_empty(&self) -> bool {
self.bins.is_empty()
}
pub fn add(&mut self, key: i32) {
let idx = self.get_index(key);
self.bins[idx] += 1;
self.count += 1;
}
fn get_index(&mut self, key: i32) -> usize {
if key < self.min_key {
if self.is_collapsed {
return 0;
}
self.extend_range(key, None);
if self.is_collapsed {
return 0;
}
} else if key > self.max_key {
self.extend_range(key, None);
}
(key - self.offset) as usize
}
fn extend_range(&mut self, key: i32, second_key: Option<i32>) {
let second_key = second_key.unwrap_or(key);
let new_min_key = i32::min(key, i32::min(second_key, self.min_key));
let new_max_key = i32::max(key, i32::max(second_key, self.max_key));
if self.is_empty() {
let new_len = self.get_new_length(new_min_key, new_max_key);
self.bins.resize(new_len, 0);
self.offset = new_min_key;
self.adjust(new_min_key, new_max_key);
} else if new_min_key >= self.min_key && new_max_key < self.offset + self.length() {
self.min_key = new_min_key;
self.max_key = new_max_key;
} else {
let new_length = self.get_new_length(new_min_key, new_max_key);
if new_length > self.length() as usize {
self.bins.resize(new_length, 0);
}
self.adjust(new_min_key, new_max_key);
}
}
fn get_new_length(&self, new_min_key: i32, new_max_key: i32) -> usize {
let desired_length = new_max_key - new_min_key + 1;
usize::min(
(CHUNK_SIZE * div_ceil(desired_length, CHUNK_SIZE)) as usize,
self.bin_limit,
)
}
fn adjust(&mut self, new_min_key: i32, new_max_key: i32) {
if new_max_key - new_min_key + 1 > self.length() {
let new_min_key = new_max_key - self.length() + 1;
if new_min_key >= self.max_key {
self.offset = new_min_key;
self.min_key = new_min_key;
self.bins.fill(0);
self.bins[0] = self.count;
} else {
let shift = self.offset - new_min_key;
if shift < 0 {
let collapse_start_index = (self.min_key - self.offset) as usize;
let collapse_end_index = (new_min_key - self.offset) as usize;
let collapsed_count: u64 = self.bins[collapse_start_index..collapse_end_index]
.iter()
.sum();
let zero_len = (new_min_key - self.min_key) as usize;
self.bins.splice(
collapse_start_index..collapse_end_index,
std::iter::repeat(0).take(zero_len),
);
self.bins[collapse_end_index] += collapsed_count;
}
self.min_key = new_min_key;
self.shift_bins(shift);
}
self.max_key = new_max_key;
self.is_collapsed = true;
} else {
self.center_bins(new_min_key, new_max_key);
self.min_key = new_min_key;
self.max_key = new_max_key;
}
}
fn shift_bins(&mut self, shift: i32) {
if shift > 0 {
let shift = shift as usize;
self.bins.rotate_right(shift);
for idx in 0..shift {
self.bins[idx] = 0;
}
} else {
let shift = shift.abs() as usize;
for idx in 0..shift {
self.bins[idx] = 0;
}
self.bins.rotate_left(shift);
}
self.offset -= shift;
}
fn center_bins(&mut self, new_min_key: i32, new_max_key: i32) {
let middle_key = new_min_key + (new_max_key - new_min_key + 1) / 2;
let shift = self.offset + self.length() / 2 - middle_key;
self.shift_bins(shift)
}
pub fn key_at_rank(&self, rank: u64) -> i32 {
let mut n = 0;
for (i, bin) in self.bins.iter().enumerate() {
n += *bin;
if n > rank {
return i as i32 + self.offset;
}
}
self.max_key
}
pub fn count(&self) -> u64 {
self.count
}
pub fn merge(&mut self, other: &Store) {
if other.count == 0 {
return;
}
if self.count == 0 {
self.copy(other);
return;
}
if other.min_key < self.min_key || other.max_key > self.max_key {
self.extend_range(other.min_key, Some(other.max_key));
}
let collapse_start_index = other.min_key - other.offset;
let mut collapse_end_index = i32::min(self.min_key, other.max_key + 1) - other.offset;
if collapse_end_index > collapse_start_index {
let collapsed_count: u64 = self.bins
[collapse_start_index as usize..collapse_end_index as usize]
.iter()
.sum();
self.bins[0] += collapsed_count;
} else {
collapse_end_index = collapse_start_index;
}
for key in (collapse_end_index + other.offset)..(other.max_key + 1) {
self.bins[(key - self.offset) as usize] += other.bins[(key - other.offset) as usize]
}
self.count += other.count;
}
fn copy(&mut self, o: &Store) {
self.bins = o.bins.clone();
self.count = o.count;
self.min_key = o.min_key;
self.max_key = o.max_key;
self.offset = o.offset;
self.bin_limit = o.bin_limit;
self.is_collapsed = o.is_collapsed;
}
}
#[cfg(test)]
mod tests {
use crate::store::Store;
#[test]
fn test_simple_store() {
let mut s = Store::new(2048);
for i in 0..2048 {
s.add(i);
}
}
#[test]
fn test_simple_store_rev() {
let mut s = Store::new(2048);
for i in 2048..0 {
s.add(i);
}
}
}