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// use crossbeam_utils::CachePadded;
// use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
// use crate::*;
// /// A concurrent, lock-free analogue to [`Vec<T>`] which can be shared safely between threads,
// /// uses interior mutability, can grow dynamically, and supports concurrent push and pop
// /// operations.
// ///
// /// ```
// /// use seqmap::SeqVec;
// ///
// /// let vec = SeqVec::<u32>::with_capacity(2);
// ///
// /// vec.push(1);
// /// vec.push(2);
// ///
// /// std::thread::scope(|s| {
// /// s.spawn(|| {
// /// assert_eq!(vec.get(0), Some(1));
// /// assert!(vec.len() >= 2);
// /// assert!(vec.len() < 4);
// /// vec.push(3);
// /// });
// /// s.spawn(|| {
// /// assert_eq!(vec.get(1), Some(2));
// /// assert!(vec.len() >= 2);
// /// assert!(vec.len() < 4);
// /// vec.push(4);
// /// });
// /// });
// ///
// /// assert_eq!(vec.get(0), Some(1));
// /// assert_eq!(vec.get(1), Some(2));
// /// assert!(
// /// (vec.get(2) == Some(3) && vec.get(3) == Some(4)) ||
// /// (vec.get(2) == Some(4) && vec.get(3) == Some(3))
// /// );
// /// ```
// pub struct SeqVec<T: Copy + Clone + Send + Sync + 'static> {
// arr: SeqArray<T>,
// len: CachePadded<AtomicUsize>,
// pushing: CachePadded<AtomicBool>,
// }
// impl<T: Copy + Clone + Send + Sync + 'static> SeqVec<T> {
// /// Creates a new [`SeqVec`] with the specified initial capacity.
// #[inline(always)]
// pub fn with_capacity(cap: usize) -> Self {
// SeqVec {
// arr: SeqArray::with_capacity(cap),
// len: CachePadded::new(AtomicUsize::new(0)),
// pushing: CachePadded::new(AtomicBool::new(false)),
// }
// }
// /// Returns the current capacity of the [`SeqVec`].
// #[inline(always)]
// pub fn capacity(&self) -> usize {
// self.arr.capacity()
// }
// /// Returns the current length of the [`SeqVec`] using [`Ordering::Acquire`] ordering.
// #[inline(always)]
// pub fn len(&self) -> usize {
// self.len.load(Ordering::Acquire)
// }
// /// Attempts to get the value at the specified index, waiting before returning in the event
// /// of a resize.
// #[inline(always)]
// pub fn get(&self, index: usize) -> Option<T> {
// if index >= self.len() {
// return None;
// }
// self.arr.get(index).ok()
// }
// /// Attempts to set the data slot at the specified index to the specified value.
// ///
// /// If a resize is in progress, this will block until the resize is complete.
// pub fn set(&self, index: usize, value: T) -> Result<Option<T>> {
// self.arr.set(index, value)
// }
// pub fn push(&self, value: T) -> usize {
// loop {
// while self.pushing.swap(true, Ordering::AcqRel) {
// std::thread::yield_now();
// }
// let idx = self.len();
// let cap = self.capacity();
// if idx < cap {
// if !self.arr.set_without_resize(cap, idx, value).is_ok() {
// // If set fails, it means the array is full or index is out of bounds
// self.pushing.store(false, Ordering::Release);
// std::thread::yield_now();
// continue;
// }
// self.len.fetch_add(1, Ordering::AcqRel);
// self.pushing.store(false, Ordering::Release);
// return idx;
// } else {
// // retry after resize
// self.arr.scale_up();
// self.pushing.store(false, Ordering::Release);
// }
// }
// }
// /// Pops the last element from the [`SeqVec`], returning it if it exists.
// ///
// /// Only one `push` or `pop` operation can be in progress at a time.
// pub fn pop(&self) -> Option<T> {
// loop {
// while self.pushing.swap(true, Ordering::AcqRel) {
// std::thread::yield_now();
// }
// let cap = self.capacity();
// let len = self.len();
// if len == 0 {
// self.pushing.store(false, Ordering::Release);
// return None;
// }
// let idx = len.saturating_sub(1);
// if idx < cap {
// let old = self.arr.get_without_resize(cap, idx);
// if matches!(old, Err(Error::Resized | Error::Resizing)) {
// // If resizing, retry
// self.pushing.store(false, Ordering::Release);
// std::thread::yield_now();
// continue;
// }
// let unset = self.arr.unset_without_resize(cap, idx);
// if matches!(unset, Err(Error::Resized | Error::Resizing)) {
// // If resizing, retry
// self.pushing.store(false, Ordering::Release);
// std::thread::yield_now();
// continue;
// }
// if old.is_err() || !unset.is_ok() {
// self.pushing.store(false, Ordering::Release);
// return None;
// }
// self.len.fetch_sub(1, Ordering::AcqRel);
// self.pushing.store(false, Ordering::Release);
// return old.ok();
// } else {
// self.pushing.store(false, Ordering::Release);
// return None;
// }
// }
// }
// /// Reserves capacity for at least `new_cap` elements in the [`SeqVec`].
// pub fn reserve(&self, new_cap: usize) {
// self.arr.reserve(new_cap);
// }
// }
// impl<T: Copy + Clone + Send + Sync + 'static> Clone for SeqVec<T> {
// fn clone(&self) -> Self {
// let arr = self.arr.clone();
// let cap = arr.capacity();
// let len = self.len.load(Ordering::Acquire);
// let len = if len > cap { cap } else { len };
// let mut new_len = 0;
// for i in 0..len {
// if let Ok(_) = arr.get(i) {
// new_len += 1;
// } else {
// break;
// }
// }
// SeqVec {
// arr,
// len: CachePadded::new(AtomicUsize::new(new_len)),
// pushing: CachePadded::new(AtomicBool::new(false)),
// }
// }
// }
// #[test]
// fn push_and_get() {
// let vec: SeqVec<usize> = SeqVec::with_capacity(8);
// let n = 1000;
// for i in 0..n {
// let idx = vec.push(i);
// assert_eq!(idx, i);
// }
// for i in 0..n {
// assert_eq!(vec.get(i), Some(i));
// }
// assert_eq!(vec.len(), n);
// }
// #[test]
// fn set_and_get_update() {
// let vec: SeqVec<usize> = SeqVec::with_capacity(16);
// for _ in 0..16 {
// vec.push(0);
// }
// for i in 0..16 {
// vec.set(i, i * 2).unwrap();
// }
// for i in 0..16 {
// assert_eq!(vec.get(i), Some(i * 2));
// }
// // Out of bounds set
// vec.set(16, 123).unwrap_err();
// assert_eq!(vec.get(16), None);
// }
// #[test]
// fn reserve_and_push_grow() {
// let vec: SeqVec<usize> = SeqVec::with_capacity(2);
// vec.reserve(100);
// for i in 0..100 {
// vec.push(i);
// }
// for i in 0..100 {
// assert_eq!(vec.get(i), Some(i));
// }
// assert_eq!(vec.len(), 100);
// assert!(vec.capacity() >= 100);
// }
// #[test]
// fn concurrent_push_unique() {
// use rayon::prelude::*;
// let vec: SeqVec<usize> = SeqVec::with_capacity(8);
// let n = 1000000;
// (0..n).into_par_iter().for_each(|i| {
// vec.push(i);
// });
// let mut seen = std::collections::HashSet::new();
// let mut missing = vec![];
// for i in 0..vec.len() {
// match vec.get(i) {
// Some(v) => {
// assert!(seen.insert(v), "Duplicate value {v}");
// }
// None => missing.push(i),
// }
// }
// assert!(
// missing.is_empty(),
// "Missing values at indices: {:?}",
// missing
// );
// assert_eq!(seen.len(), n);
// }
// #[test]
// fn push_and_pop_lifo() {
// let vec: SeqVec<i32> = SeqVec::with_capacity(8);
// let n = 1000;
// for i in 0..n {
// vec.push(i);
// }
// for i in (0..n).rev() {
// assert_eq!(vec.pop(), Some(i));
// }
// assert_eq!(vec.len(), 0);
// assert_eq!(vec.pop(), None);
// }
// #[test]
// fn interleaved_push_pop_varied() {
// let vec: SeqVec<i32> = SeqVec::with_capacity(4);
// assert_eq!(vec.pop(), None);
// let a = vec.push(1);
// let b = vec.push(2);
// assert_eq!(a, 0);
// assert_eq!(b, 1);
// assert_eq!(vec.pop(), Some(2));
// assert_eq!(vec.pop(), Some(1));
// assert_eq!(vec.pop(), None);
// let c = vec.push(42);
// assert_eq!(c, 0);
// assert_eq!(vec.pop(), Some(42));
// assert_eq!(vec.pop(), None);
// }
// #[test]
// fn concurrent_push_and_pop_unique() {
// use rayon::prelude::*;
// let vec: SeqVec<i32> = SeqVec::with_capacity(8);
// let n = 10000;
// // Push in parallel
// (0..n).into_par_iter().for_each(|i| {
// vec.push(i);
// });
// // Pop in parallel
// let pops: Vec<_> = (0..n).into_par_iter().map(|_| vec.pop()).collect();
// // All pops should be Some and unique, and after n pops, len should be 0
// let mut seen = std::collections::HashSet::new();
// let mut missing = vec![];
// for v in pops {
// match v {
// Some(x) => {
// assert!(seen.insert(x), "Duplicate value {x}");
// }
// None => missing.push(()),
// }
// }
// assert!(missing.len() == 0, "Some pops returned None before empty");
// assert_eq!(vec.len(), 0);
// // Further pops should be None
// assert_eq!(vec.pop(), None);
// }
// #[test]
// fn concurrent_interleaved_push_pop_varied() {
// use rayon::prelude::*;
// let vec: SeqVec<usize> = SeqVec::with_capacity(8);
// let n = 10000;
// // Interleave push and pop in parallel
// let results: Vec<_> = (0..n)
// .into_par_iter()
// .map(|i| {
// if i % 2 == 0 {
// Some(vec.push(i))
// } else {
// vec.pop();
// None // marker for pop
// }
// })
// .collect();
// // Count how many pushes succeeded
// let _push_count = results.iter().filter(|x| x.is_some()).count();
// // After all, len should be >= 0 and <= n/2 (since half are pops)
// assert!(vec.len() <= n / 2);
// // All remaining values in the vector should be unique
// let mut seen = std::collections::HashSet::new();
// for i in 0..vec.len() {
// let v = vec.get(i).unwrap();
// assert!(seen.insert(v), "Duplicate value {v}");
// }
// }
// #[test]
// fn clone_basic() {
// let vec: SeqVec<usize> = SeqVec::with_capacity(16);
// for i in 0..10 {
// vec.push(i);
// }
// let clone = vec.clone();
// assert_eq!(clone.len(), 10);
// for i in 0..10 {
// assert_eq!(clone.get(i), Some(i));
// }
// // Mutate original, clone should not change
// vec.set(0, 42).unwrap();
// assert_eq!(clone.get(0), Some(0));
// }
// #[test]
// fn clone_after_grow() {
// let vec: SeqVec<usize> = SeqVec::with_capacity(2);
// for i in 0..100 {
// vec.push(i);
// }
// let clone = vec.clone();
// assert_eq!(clone.len(), 100);
// for i in 0..100 {
// assert_eq!(clone.get(i), Some(i));
// }
// }
// #[test]
// fn clone_during_concurrent_growth() {
// use std::thread;
// let vec: SeqVec<i32> = SeqVec::with_capacity(4);
// let n = 10_000;
// thread::scope(|s| {
// // Writer: grows and fills the vector
// let writer = s.spawn(|| {
// for i in 0..n {
// vec.push(i);
// }
// });
// // Cloner: repeatedly clones the vector while it is growing
// let cloner = s.spawn(|| {
// let mut last_len = 0;
// for _ in 0..100 {
// let clone = vec.clone();
// assert!(clone.len() >= last_len, "Clone length should not decrease");
// for i in 0..clone.len() {
// let v = clone.get(i).unwrap();
// assert!(v < n, "Cloned value out of range");
// }
// last_len = clone.len();
// }
// });
// writer.join().unwrap();
// cloner.join().unwrap();
// });
// }