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Diffstat (limited to 'compiler/rustc_index/src/bit_set.rs')
| -rw-r--r-- | compiler/rustc_index/src/bit_set.rs | 2098 |
1 files changed, 2098 insertions, 0 deletions
diff --git a/compiler/rustc_index/src/bit_set.rs b/compiler/rustc_index/src/bit_set.rs new file mode 100644 index 000000000..777112442 --- /dev/null +++ b/compiler/rustc_index/src/bit_set.rs @@ -0,0 +1,2098 @@ +use crate::vec::{Idx, IndexVec}; +use arrayvec::ArrayVec; +use std::fmt; +use std::iter; +use std::marker::PhantomData; +use std::mem; +use std::ops::{BitAnd, BitAndAssign, BitOrAssign, Bound, Not, Range, RangeBounds, Shl}; +use std::rc::Rc; +use std::slice; + +use rustc_macros::{Decodable, Encodable}; + +use Chunk::*; + +#[cfg(test)] +mod tests; + +type Word = u64; +const WORD_BYTES: usize = mem::size_of::<Word>(); +const WORD_BITS: usize = WORD_BYTES * 8; + +// The choice of chunk size has some trade-offs. +// +// A big chunk size tends to favour cases where many large `ChunkedBitSet`s are +// present, because they require fewer `Chunk`s, reducing the number of +// allocations and reducing peak memory usage. Also, fewer chunk operations are +// required, though more of them might be `Mixed`. +// +// A small chunk size tends to favour cases where many small `ChunkedBitSet`s +// are present, because less space is wasted at the end of the final chunk (if +// it's not full). +const CHUNK_WORDS: usize = 32; +const CHUNK_BITS: usize = CHUNK_WORDS * WORD_BITS; // 2048 bits + +/// ChunkSize is small to keep `Chunk` small. The static assertion ensures it's +/// not too small. +type ChunkSize = u16; +const _: () = assert!(CHUNK_BITS <= ChunkSize::MAX as usize); + +pub trait BitRelations<Rhs> { + fn union(&mut self, other: &Rhs) -> bool; + fn subtract(&mut self, other: &Rhs) -> bool; + fn intersect(&mut self, other: &Rhs) -> bool; +} + +#[inline] +fn inclusive_start_end<T: Idx>( + range: impl RangeBounds<T>, + domain: usize, +) -> Option<(usize, usize)> { + // Both start and end are inclusive. + let start = match range.start_bound().cloned() { + Bound::Included(start) => start.index(), + Bound::Excluded(start) => start.index() + 1, + Bound::Unbounded => 0, + }; + let end = match range.end_bound().cloned() { + Bound::Included(end) => end.index(), + Bound::Excluded(end) => end.index().checked_sub(1)?, + Bound::Unbounded => domain - 1, + }; + assert!(end < domain); + if start > end { + return None; + } + Some((start, end)) +} + +macro_rules! bit_relations_inherent_impls { + () => { + /// Sets `self = self | other` and returns `true` if `self` changed + /// (i.e., if new bits were added). + pub fn union<Rhs>(&mut self, other: &Rhs) -> bool + where + Self: BitRelations<Rhs>, + { + <Self as BitRelations<Rhs>>::union(self, other) + } + + /// Sets `self = self - other` and returns `true` if `self` changed. + /// (i.e., if any bits were removed). + pub fn subtract<Rhs>(&mut self, other: &Rhs) -> bool + where + Self: BitRelations<Rhs>, + { + <Self as BitRelations<Rhs>>::subtract(self, other) + } + + /// Sets `self = self & other` and return `true` if `self` changed. + /// (i.e., if any bits were removed). + pub fn intersect<Rhs>(&mut self, other: &Rhs) -> bool + where + Self: BitRelations<Rhs>, + { + <Self as BitRelations<Rhs>>::intersect(self, other) + } + }; +} + +/// A fixed-size bitset type with a dense representation. +/// +/// NOTE: Use [`GrowableBitSet`] if you need support for resizing after creation. +/// +/// `T` is an index type, typically a newtyped `usize` wrapper, but it can also +/// just be `usize`. +/// +/// All operations that involve an element will panic if the element is equal +/// to or greater than the domain size. All operations that involve two bitsets +/// will panic if the bitsets have differing domain sizes. +/// +#[derive(Eq, PartialEq, Hash, Decodable, Encodable)] +pub struct BitSet<T> { + domain_size: usize, + words: Vec<Word>, + marker: PhantomData<T>, +} + +impl<T> BitSet<T> { + /// Gets the domain size. + pub fn domain_size(&self) -> usize { + self.domain_size + } +} + +impl<T: Idx> BitSet<T> { + /// Creates a new, empty bitset with a given `domain_size`. + #[inline] + pub fn new_empty(domain_size: usize) -> BitSet<T> { + let num_words = num_words(domain_size); + BitSet { domain_size, words: vec![0; num_words], marker: PhantomData } + } + + /// Creates a new, filled bitset with a given `domain_size`. + #[inline] + pub fn new_filled(domain_size: usize) -> BitSet<T> { + let num_words = num_words(domain_size); + let mut result = BitSet { domain_size, words: vec![!0; num_words], marker: PhantomData }; + result.clear_excess_bits(); + result + } + + /// Clear all elements. + #[inline] + pub fn clear(&mut self) { + self.words.fill(0); + } + + /// Clear excess bits in the final word. + fn clear_excess_bits(&mut self) { + clear_excess_bits_in_final_word(self.domain_size, &mut self.words); + } + + /// Count the number of set bits in the set. + pub fn count(&self) -> usize { + self.words.iter().map(|e| e.count_ones() as usize).sum() + } + + /// Returns `true` if `self` contains `elem`. + #[inline] + pub fn contains(&self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + let (word_index, mask) = word_index_and_mask(elem); + (self.words[word_index] & mask) != 0 + } + + /// Is `self` is a (non-strict) superset of `other`? + #[inline] + pub fn superset(&self, other: &BitSet<T>) -> bool { + assert_eq!(self.domain_size, other.domain_size); + self.words.iter().zip(&other.words).all(|(a, b)| (a & b) == *b) + } + + /// Is the set empty? + #[inline] + pub fn is_empty(&self) -> bool { + self.words.iter().all(|a| *a == 0) + } + + /// Insert `elem`. Returns whether the set has changed. + #[inline] + pub fn insert(&mut self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + let (word_index, mask) = word_index_and_mask(elem); + let word_ref = &mut self.words[word_index]; + let word = *word_ref; + let new_word = word | mask; + *word_ref = new_word; + new_word != word + } + + #[inline] + pub fn insert_range(&mut self, elems: impl RangeBounds<T>) { + let Some((start, end)) = inclusive_start_end(elems, self.domain_size) else { + return; + }; + + let (start_word_index, start_mask) = word_index_and_mask(start); + let (end_word_index, end_mask) = word_index_and_mask(end); + + // Set all words in between start and end (exclusively of both). + for word_index in (start_word_index + 1)..end_word_index { + self.words[word_index] = !0; + } + + if start_word_index != end_word_index { + // Start and end are in different words, so we handle each in turn. + // + // We set all leading bits. This includes the start_mask bit. + self.words[start_word_index] |= !(start_mask - 1); + // And all trailing bits (i.e. from 0..=end) in the end word, + // including the end. + self.words[end_word_index] |= end_mask | end_mask - 1; + } else { + self.words[start_word_index] |= end_mask | (end_mask - start_mask); + } + } + + /// Sets all bits to true. + pub fn insert_all(&mut self) { + self.words.fill(!0); + self.clear_excess_bits(); + } + + /// Returns `true` if the set has changed. + #[inline] + pub fn remove(&mut self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + let (word_index, mask) = word_index_and_mask(elem); + let word_ref = &mut self.words[word_index]; + let word = *word_ref; + let new_word = word & !mask; + *word_ref = new_word; + new_word != word + } + + /// Gets a slice of the underlying words. + pub fn words(&self) -> &[Word] { + &self.words + } + + /// Iterates over the indices of set bits in a sorted order. + #[inline] + pub fn iter(&self) -> BitIter<'_, T> { + BitIter::new(&self.words) + } + + /// Duplicates the set as a hybrid set. + pub fn to_hybrid(&self) -> HybridBitSet<T> { + // Note: we currently don't bother trying to make a Sparse set. + HybridBitSet::Dense(self.to_owned()) + } + + /// Set `self = self | other`. In contrast to `union` returns `true` if the set contains at + /// least one bit that is not in `other` (i.e. `other` is not a superset of `self`). + /// + /// This is an optimization for union of a hybrid bitset. + fn reverse_union_sparse(&mut self, sparse: &SparseBitSet<T>) -> bool { + assert!(sparse.domain_size == self.domain_size); + self.clear_excess_bits(); + + let mut not_already = false; + // Index of the current word not yet merged. + let mut current_index = 0; + // Mask of bits that came from the sparse set in the current word. + let mut new_bit_mask = 0; + for (word_index, mask) in sparse.iter().map(|x| word_index_and_mask(*x)) { + // Next bit is in a word not inspected yet. + if word_index > current_index { + self.words[current_index] |= new_bit_mask; + // Were there any bits in the old word that did not occur in the sparse set? + not_already |= (self.words[current_index] ^ new_bit_mask) != 0; + // Check all words we skipped for any set bit. + not_already |= self.words[current_index + 1..word_index].iter().any(|&x| x != 0); + // Update next word. + current_index = word_index; + // Reset bit mask, no bits have been merged yet. + new_bit_mask = 0; + } + // Add bit and mark it as coming from the sparse set. + // self.words[word_index] |= mask; + new_bit_mask |= mask; + } + self.words[current_index] |= new_bit_mask; + // Any bits in the last inspected word that were not in the sparse set? + not_already |= (self.words[current_index] ^ new_bit_mask) != 0; + // Any bits in the tail? Note `clear_excess_bits` before. + not_already |= self.words[current_index + 1..].iter().any(|&x| x != 0); + + not_already + } + + fn last_set_in(&self, range: impl RangeBounds<T>) -> Option<T> { + let (start, end) = inclusive_start_end(range, self.domain_size)?; + let (start_word_index, _) = word_index_and_mask(start); + let (end_word_index, end_mask) = word_index_and_mask(end); + + let end_word = self.words[end_word_index] & (end_mask | (end_mask - 1)); + if end_word != 0 { + let pos = max_bit(end_word) + WORD_BITS * end_word_index; + if start <= pos { + return Some(T::new(pos)); + } + } + + // We exclude end_word_index from the range here, because we don't want + // to limit ourselves to *just* the last word: the bits set it in may be + // after `end`, so it may not work out. + if let Some(offset) = + self.words[start_word_index..end_word_index].iter().rposition(|&w| w != 0) + { + let word_idx = start_word_index + offset; + let start_word = self.words[word_idx]; + let pos = max_bit(start_word) + WORD_BITS * word_idx; + if start <= pos { + return Some(T::new(pos)); + } + } + + None + } + + bit_relations_inherent_impls! {} +} + +// dense REL dense +impl<T: Idx> BitRelations<BitSet<T>> for BitSet<T> { + fn union(&mut self, other: &BitSet<T>) -> bool { + assert_eq!(self.domain_size, other.domain_size); + bitwise(&mut self.words, &other.words, |a, b| a | b) + } + + fn subtract(&mut self, other: &BitSet<T>) -> bool { + assert_eq!(self.domain_size, other.domain_size); + bitwise(&mut self.words, &other.words, |a, b| a & !b) + } + + fn intersect(&mut self, other: &BitSet<T>) -> bool { + assert_eq!(self.domain_size, other.domain_size); + bitwise(&mut self.words, &other.words, |a, b| a & b) + } +} + +impl<T: Idx> From<GrowableBitSet<T>> for BitSet<T> { + fn from(bit_set: GrowableBitSet<T>) -> Self { + bit_set.bit_set + } +} + +/// A fixed-size bitset type with a partially dense, partially sparse +/// representation. The bitset is broken into chunks, and chunks that are all +/// zeros or all ones are represented and handled very efficiently. +/// +/// This type is especially efficient for sets that typically have a large +/// `domain_size` with significant stretches of all zeros or all ones, and also +/// some stretches with lots of 0s and 1s mixed in a way that causes trouble +/// for `IntervalSet`. +/// +/// `T` is an index type, typically a newtyped `usize` wrapper, but it can also +/// just be `usize`. +/// +/// All operations that involve an element will panic if the element is equal +/// to or greater than the domain size. All operations that involve two bitsets +/// will panic if the bitsets have differing domain sizes. +#[derive(Debug, PartialEq, Eq)] +pub struct ChunkedBitSet<T> { + domain_size: usize, + + /// The chunks. Each one contains exactly CHUNK_BITS values, except the + /// last one which contains 1..=CHUNK_BITS values. + chunks: Box<[Chunk]>, + + marker: PhantomData<T>, +} + +// Note: the chunk domain size is duplicated in each variant. This is a bit +// inconvenient, but it allows the type size to be smaller than if we had an +// outer struct containing a chunk domain size plus the `Chunk`, because the +// compiler can place the chunk domain size after the tag. +#[derive(Clone, Debug, PartialEq, Eq)] +enum Chunk { + /// A chunk that is all zeros; we don't represent the zeros explicitly. + Zeros(ChunkSize), + + /// A chunk that is all ones; we don't represent the ones explicitly. + Ones(ChunkSize), + + /// A chunk that has a mix of zeros and ones, which are represented + /// explicitly and densely. It never has all zeros or all ones. + /// + /// If this is the final chunk there may be excess, unused words. This + /// turns out to be both simpler and have better performance than + /// allocating the minimum number of words, largely because we avoid having + /// to store the length, which would make this type larger. These excess + /// words are always be zero, as are any excess bits in the final in-use + /// word. + /// + /// The second field is the count of 1s set in the chunk, and must satisfy + /// `0 < count < chunk_domain_size`. + /// + /// The words are within an `Rc` because it's surprisingly common to + /// duplicate an entire chunk, e.g. in `ChunkedBitSet::clone_from()`, or + /// when a `Mixed` chunk is union'd into a `Zeros` chunk. When we do need + /// to modify a chunk we use `Rc::make_mut`. + Mixed(ChunkSize, ChunkSize, Rc<[Word; CHUNK_WORDS]>), +} + +// This type is used a lot. Make sure it doesn't unintentionally get bigger. +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +crate::static_assert_size!(Chunk, 16); + +impl<T> ChunkedBitSet<T> { + pub fn domain_size(&self) -> usize { + self.domain_size + } + + #[cfg(test)] + fn assert_valid(&self) { + if self.domain_size == 0 { + assert!(self.chunks.is_empty()); + return; + } + + assert!((self.chunks.len() - 1) * CHUNK_BITS <= self.domain_size); + assert!(self.chunks.len() * CHUNK_BITS >= self.domain_size); + for chunk in self.chunks.iter() { + chunk.assert_valid(); + } + } +} + +impl<T: Idx> ChunkedBitSet<T> { + /// Creates a new bitset with a given `domain_size` and chunk kind. + fn new(domain_size: usize, is_empty: bool) -> Self { + let chunks = if domain_size == 0 { + Box::new([]) + } else { + // All the chunks have a chunk_domain_size of `CHUNK_BITS` except + // the final one. + let final_chunk_domain_size = { + let n = domain_size % CHUNK_BITS; + if n == 0 { CHUNK_BITS } else { n } + }; + let mut chunks = + vec![Chunk::new(CHUNK_BITS, is_empty); num_chunks(domain_size)].into_boxed_slice(); + *chunks.last_mut().unwrap() = Chunk::new(final_chunk_domain_size, is_empty); + chunks + }; + ChunkedBitSet { domain_size, chunks, marker: PhantomData } + } + + /// Creates a new, empty bitset with a given `domain_size`. + #[inline] + pub fn new_empty(domain_size: usize) -> Self { + ChunkedBitSet::new(domain_size, /* is_empty */ true) + } + + /// Creates a new, filled bitset with a given `domain_size`. + #[inline] + pub fn new_filled(domain_size: usize) -> Self { + ChunkedBitSet::new(domain_size, /* is_empty */ false) + } + + #[cfg(test)] + fn chunks(&self) -> &[Chunk] { + &self.chunks + } + + /// Count the number of bits in the set. + pub fn count(&self) -> usize { + self.chunks.iter().map(|chunk| chunk.count()).sum() + } + + /// Returns `true` if `self` contains `elem`. + #[inline] + pub fn contains(&self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + let chunk = &self.chunks[chunk_index(elem)]; + match &chunk { + Zeros(_) => false, + Ones(_) => true, + Mixed(_, _, words) => { + let (word_index, mask) = chunk_word_index_and_mask(elem); + (words[word_index] & mask) != 0 + } + } + } + + #[inline] + pub fn iter(&self) -> ChunkedBitIter<'_, T> { + ChunkedBitIter::new(self) + } + + /// Insert `elem`. Returns whether the set has changed. + pub fn insert(&mut self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + let chunk_index = chunk_index(elem); + let chunk = &mut self.chunks[chunk_index]; + match *chunk { + Zeros(chunk_domain_size) => { + if chunk_domain_size > 1 { + // We take some effort to avoid copying the words. + let words = Rc::<[Word; CHUNK_WORDS]>::new_zeroed(); + // SAFETY: `words` can safely be all zeroes. + let mut words = unsafe { words.assume_init() }; + let words_ref = Rc::get_mut(&mut words).unwrap(); + + let (word_index, mask) = chunk_word_index_and_mask(elem); + words_ref[word_index] |= mask; + *chunk = Mixed(chunk_domain_size, 1, words); + } else { + *chunk = Ones(chunk_domain_size); + } + true + } + Ones(_) => false, + Mixed(chunk_domain_size, ref mut count, ref mut words) => { + // We skip all the work if the bit is already set. + let (word_index, mask) = chunk_word_index_and_mask(elem); + if (words[word_index] & mask) == 0 { + *count += 1; + if *count < chunk_domain_size { + let words = Rc::make_mut(words); + words[word_index] |= mask; + } else { + *chunk = Ones(chunk_domain_size); + } + true + } else { + false + } + } + } + } + + /// Sets all bits to true. + pub fn insert_all(&mut self) { + for chunk in self.chunks.iter_mut() { + *chunk = match *chunk { + Zeros(chunk_domain_size) + | Ones(chunk_domain_size) + | Mixed(chunk_domain_size, ..) => Ones(chunk_domain_size), + } + } + } + + /// Returns `true` if the set has changed. + pub fn remove(&mut self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + let chunk_index = chunk_index(elem); + let chunk = &mut self.chunks[chunk_index]; + match *chunk { + Zeros(_) => false, + Ones(chunk_domain_size) => { + if chunk_domain_size > 1 { + // We take some effort to avoid copying the words. + let words = Rc::<[Word; CHUNK_WORDS]>::new_zeroed(); + // SAFETY: `words` can safely be all zeroes. + let mut words = unsafe { words.assume_init() }; + let words_ref = Rc::get_mut(&mut words).unwrap(); + + // Set only the bits in use. + let num_words = num_words(chunk_domain_size as usize); + words_ref[..num_words].fill(!0); + clear_excess_bits_in_final_word( + chunk_domain_size as usize, + &mut words_ref[..num_words], + ); + let (word_index, mask) = chunk_word_index_and_mask(elem); + words_ref[word_index] &= !mask; + *chunk = Mixed(chunk_domain_size, chunk_domain_size - 1, words); + } else { + *chunk = Zeros(chunk_domain_size); + } + true + } + Mixed(chunk_domain_size, ref mut count, ref mut words) => { + // We skip all the work if the bit is already clear. + let (word_index, mask) = chunk_word_index_and_mask(elem); + if (words[word_index] & mask) != 0 { + *count -= 1; + if *count > 0 { + let words = Rc::make_mut(words); + words[word_index] &= !mask; + } else { + *chunk = Zeros(chunk_domain_size); + } + true + } else { + false + } + } + } + } + + bit_relations_inherent_impls! {} +} + +impl<T: Idx> BitRelations<ChunkedBitSet<T>> for ChunkedBitSet<T> { + fn union(&mut self, other: &ChunkedBitSet<T>) -> bool { + assert_eq!(self.domain_size, other.domain_size); + debug_assert_eq!(self.chunks.len(), other.chunks.len()); + + let mut changed = false; + for (mut self_chunk, other_chunk) in self.chunks.iter_mut().zip(other.chunks.iter()) { + match (&mut self_chunk, &other_chunk) { + (_, Zeros(_)) | (Ones(_), _) => {} + (Zeros(self_chunk_domain_size), Ones(other_chunk_domain_size)) + | (Mixed(self_chunk_domain_size, ..), Ones(other_chunk_domain_size)) + | (Zeros(self_chunk_domain_size), Mixed(other_chunk_domain_size, ..)) => { + // `other_chunk` fully overwrites `self_chunk` + debug_assert_eq!(self_chunk_domain_size, other_chunk_domain_size); + *self_chunk = other_chunk.clone(); + changed = true; + } + ( + Mixed( + self_chunk_domain_size, + ref mut self_chunk_count, + ref mut self_chunk_words, + ), + Mixed(_other_chunk_domain_size, _other_chunk_count, other_chunk_words), + ) => { + // First check if the operation would change + // `self_chunk.words`. If not, we can avoid allocating some + // words, and this happens often enough that it's a + // performance win. Also, we only need to operate on the + // in-use words, hence the slicing. + let op = |a, b| a | b; + let num_words = num_words(*self_chunk_domain_size as usize); + if bitwise_changes( + &self_chunk_words[0..num_words], + &other_chunk_words[0..num_words], + op, + ) { + let self_chunk_words = Rc::make_mut(self_chunk_words); + let has_changed = bitwise( + &mut self_chunk_words[0..num_words], + &other_chunk_words[0..num_words], + op, + ); + debug_assert!(has_changed); + *self_chunk_count = self_chunk_words[0..num_words] + .iter() + .map(|w| w.count_ones() as ChunkSize) + .sum(); + if *self_chunk_count == *self_chunk_domain_size { + *self_chunk = Ones(*self_chunk_domain_size); + } + changed = true; + } + } + } + } + changed + } + + fn subtract(&mut self, _other: &ChunkedBitSet<T>) -> bool { + unimplemented!("implement if/when necessary"); + } + + fn intersect(&mut self, _other: &ChunkedBitSet<T>) -> bool { + unimplemented!("implement if/when necessary"); + } +} + +impl<T: Idx> BitRelations<HybridBitSet<T>> for ChunkedBitSet<T> { + fn union(&mut self, other: &HybridBitSet<T>) -> bool { + // FIXME: This is slow if `other` is dense, but it hasn't been a problem + // in practice so far. + // If a faster implementation of this operation is required, consider + // reopening https://github.com/rust-lang/rust/pull/94625 + assert_eq!(self.domain_size, other.domain_size()); + sequential_update(|elem| self.insert(elem), other.iter()) + } + + fn subtract(&mut self, other: &HybridBitSet<T>) -> bool { + // FIXME: This is slow if `other` is dense, but it hasn't been a problem + // in practice so far. + // If a faster implementation of this operation is required, consider + // reopening https://github.com/rust-lang/rust/pull/94625 + assert_eq!(self.domain_size, other.domain_size()); + sequential_update(|elem| self.remove(elem), other.iter()) + } + + fn intersect(&mut self, _other: &HybridBitSet<T>) -> bool { + unimplemented!("implement if/when necessary"); + } +} + +impl<T: Idx> BitRelations<ChunkedBitSet<T>> for BitSet<T> { + fn union(&mut self, other: &ChunkedBitSet<T>) -> bool { + sequential_update(|elem| self.insert(elem), other.iter()) + } + + fn subtract(&mut self, _other: &ChunkedBitSet<T>) -> bool { + unimplemented!("implement if/when necessary"); + } + + fn intersect(&mut self, other: &ChunkedBitSet<T>) -> bool { + assert_eq!(self.domain_size(), other.domain_size); + let mut changed = false; + for (i, chunk) in other.chunks.iter().enumerate() { + let mut words = &mut self.words[i * CHUNK_WORDS..]; + if words.len() > CHUNK_WORDS { + words = &mut words[..CHUNK_WORDS]; + } + match chunk { + Chunk::Zeros(..) => { + for word in words { + if *word != 0 { + changed = true; + *word = 0; + } + } + } + Chunk::Ones(..) => (), + Chunk::Mixed(_, _, data) => { + for (i, word) in words.iter_mut().enumerate() { + let new_val = *word & data[i]; + if new_val != *word { + changed = true; + *word = new_val; + } + } + } + } + } + changed + } +} + +impl<T> Clone for ChunkedBitSet<T> { + fn clone(&self) -> Self { + ChunkedBitSet { + domain_size: self.domain_size, + chunks: self.chunks.clone(), + marker: PhantomData, + } + } + + /// WARNING: this implementation of clone_from will panic if the two + /// bitsets have different domain sizes. This constraint is not inherent to + /// `clone_from`, but it works with the existing call sites and allows a + /// faster implementation, which is important because this function is hot. + fn clone_from(&mut self, from: &Self) { + assert_eq!(self.domain_size, from.domain_size); + debug_assert_eq!(self.chunks.len(), from.chunks.len()); + + self.chunks.clone_from(&from.chunks) + } +} + +pub struct ChunkedBitIter<'a, T: Idx> { + index: usize, + bitset: &'a ChunkedBitSet<T>, +} + +impl<'a, T: Idx> ChunkedBitIter<'a, T> { + #[inline] + fn new(bitset: &'a ChunkedBitSet<T>) -> ChunkedBitIter<'a, T> { + ChunkedBitIter { index: 0, bitset } + } +} + +impl<'a, T: Idx> Iterator for ChunkedBitIter<'a, T> { + type Item = T; + fn next(&mut self) -> Option<T> { + while self.index < self.bitset.domain_size() { + let elem = T::new(self.index); + let chunk = &self.bitset.chunks[chunk_index(elem)]; + match &chunk { + Zeros(chunk_domain_size) => { + self.index += *chunk_domain_size as usize; + } + Ones(_chunk_domain_size) => { + self.index += 1; + return Some(elem); + } + Mixed(_chunk_domain_size, _, words) => loop { + let elem = T::new(self.index); + self.index += 1; + let (word_index, mask) = chunk_word_index_and_mask(elem); + if (words[word_index] & mask) != 0 { + return Some(elem); + } + if self.index % CHUNK_BITS == 0 { + break; + } + }, + } + } + None + } + + fn fold<B, F>(mut self, mut init: B, mut f: F) -> B + where + F: FnMut(B, Self::Item) -> B, + { + // If `next` has already been called, we may not be at the start of a chunk, so we first + // advance the iterator to the start of the next chunk, before proceeding in chunk sized + // steps. + while self.index % CHUNK_BITS != 0 { + let Some(item) = self.next() else { + return init + }; + init = f(init, item); + } + let start_chunk = self.index / CHUNK_BITS; + let chunks = &self.bitset.chunks[start_chunk..]; + for (i, chunk) in chunks.iter().enumerate() { + let base = (start_chunk + i) * CHUNK_BITS; + match chunk { + Chunk::Zeros(_) => (), + Chunk::Ones(limit) => { + for j in 0..(*limit as usize) { + init = f(init, T::new(base + j)); + } + } + Chunk::Mixed(_, _, words) => { + init = BitIter::new(&**words).fold(init, |val, mut item: T| { + item.increment_by(base); + f(val, item) + }); + } + } + } + init + } +} + +impl Chunk { + #[cfg(test)] + fn assert_valid(&self) { + match *self { + Zeros(chunk_domain_size) | Ones(chunk_domain_size) => { + assert!(chunk_domain_size as usize <= CHUNK_BITS); + } + Mixed(chunk_domain_size, count, ref words) => { + assert!(chunk_domain_size as usize <= CHUNK_BITS); + assert!(0 < count && count < chunk_domain_size); + + // Check the number of set bits matches `count`. + assert_eq!( + words.iter().map(|w| w.count_ones() as ChunkSize).sum::<ChunkSize>(), + count + ); + + // Check the not-in-use words are all zeroed. + let num_words = num_words(chunk_domain_size as usize); + if num_words < CHUNK_WORDS { + assert_eq!( + words[num_words..] + .iter() + .map(|w| w.count_ones() as ChunkSize) + .sum::<ChunkSize>(), + 0 + ); + } + } + } + } + + fn new(chunk_domain_size: usize, is_empty: bool) -> Self { + debug_assert!(chunk_domain_size <= CHUNK_BITS); + let chunk_domain_size = chunk_domain_size as ChunkSize; + if is_empty { Zeros(chunk_domain_size) } else { Ones(chunk_domain_size) } + } + + /// Count the number of 1s in the chunk. + fn count(&self) -> usize { + match *self { + Zeros(_) => 0, + Ones(chunk_domain_size) => chunk_domain_size as usize, + Mixed(_, count, _) => count as usize, + } + } +} + +// Applies a function to mutate a bitset, and returns true if any +// of the applications return true +fn sequential_update<T: Idx>( + mut self_update: impl FnMut(T) -> bool, + it: impl Iterator<Item = T>, +) -> bool { + it.fold(false, |changed, elem| self_update(elem) | changed) +} + +// Optimization of intersection for SparseBitSet that's generic +// over the RHS +fn sparse_intersect<T: Idx>( + set: &mut SparseBitSet<T>, + other_contains: impl Fn(&T) -> bool, +) -> bool { + let size = set.elems.len(); + set.elems.retain(|elem| other_contains(elem)); + set.elems.len() != size +} + +// Optimization of dense/sparse intersection. The resulting set is +// guaranteed to be at most the size of the sparse set, and hence can be +// represented as a sparse set. Therefore the sparse set is copied and filtered, +// then returned as the new set. +fn dense_sparse_intersect<T: Idx>( + dense: &BitSet<T>, + sparse: &SparseBitSet<T>, +) -> (SparseBitSet<T>, bool) { + let mut sparse_copy = sparse.clone(); + sparse_intersect(&mut sparse_copy, |el| dense.contains(*el)); + let n = sparse_copy.len(); + (sparse_copy, n != dense.count()) +} + +// hybrid REL dense +impl<T: Idx> BitRelations<BitSet<T>> for HybridBitSet<T> { + fn union(&mut self, other: &BitSet<T>) -> bool { + assert_eq!(self.domain_size(), other.domain_size); + match self { + HybridBitSet::Sparse(sparse) => { + // `self` is sparse and `other` is dense. To + // merge them, we have two available strategies: + // * Densify `self` then merge other + // * Clone other then integrate bits from `self` + // The second strategy requires dedicated method + // since the usual `union` returns the wrong + // result. In the dedicated case the computation + // is slightly faster if the bits of the sparse + // bitset map to only few words of the dense + // representation, i.e. indices are near each + // other. + // + // Benchmarking seems to suggest that the second + // option is worth it. + let mut new_dense = other.clone(); + let changed = new_dense.reverse_union_sparse(sparse); + *self = HybridBitSet::Dense(new_dense); + changed + } + + HybridBitSet::Dense(dense) => dense.union(other), + } + } + + fn subtract(&mut self, other: &BitSet<T>) -> bool { + assert_eq!(self.domain_size(), other.domain_size); + match self { + HybridBitSet::Sparse(sparse) => { + sequential_update(|elem| sparse.remove(elem), other.iter()) + } + HybridBitSet::Dense(dense) => dense.subtract(other), + } + } + + fn intersect(&mut self, other: &BitSet<T>) -> bool { + assert_eq!(self.domain_size(), other.domain_size); + match self { + HybridBitSet::Sparse(sparse) => sparse_intersect(sparse, |elem| other.contains(*elem)), + HybridBitSet::Dense(dense) => dense.intersect(other), + } + } +} + +// dense REL hybrid +impl<T: Idx> BitRelations<HybridBitSet<T>> for BitSet<T> { + fn union(&mut self, other: &HybridBitSet<T>) -> bool { + assert_eq!(self.domain_size, other.domain_size()); + match other { + HybridBitSet::Sparse(sparse) => { + sequential_update(|elem| self.insert(elem), sparse.iter().cloned()) + } + HybridBitSet::Dense(dense) => self.union(dense), + } + } + + fn subtract(&mut self, other: &HybridBitSet<T>) -> bool { + assert_eq!(self.domain_size, other.domain_size()); + match other { + HybridBitSet::Sparse(sparse) => { + sequential_update(|elem| self.remove(elem), sparse.iter().cloned()) + } + HybridBitSet::Dense(dense) => self.subtract(dense), + } + } + + fn intersect(&mut self, other: &HybridBitSet<T>) -> bool { + assert_eq!(self.domain_size, other.domain_size()); + match other { + HybridBitSet::Sparse(sparse) => { + let (updated, changed) = dense_sparse_intersect(self, sparse); + + // We can't directly assign the SparseBitSet to the BitSet, and + // doing `*self = updated.to_dense()` would cause a drop / reallocation. Instead, + // the BitSet is cleared and `updated` is copied into `self`. + self.clear(); + for elem in updated.iter() { + self.insert(*elem); + } + changed + } + HybridBitSet::Dense(dense) => self.intersect(dense), + } + } +} + +// hybrid REL hybrid +impl<T: Idx> BitRelations<HybridBitSet<T>> for HybridBitSet<T> { + fn union(&mut self, other: &HybridBitSet<T>) -> bool { + assert_eq!(self.domain_size(), other.domain_size()); + match self { + HybridBitSet::Sparse(_) => { + match other { + HybridBitSet::Sparse(other_sparse) => { + // Both sets are sparse. Add the elements in + // `other_sparse` to `self` one at a time. This + // may or may not cause `self` to be densified. + let mut changed = false; + for elem in other_sparse.iter() { + changed |= self.insert(*elem); + } + changed + } + + HybridBitSet::Dense(other_dense) => self.union(other_dense), + } + } + + HybridBitSet::Dense(self_dense) => self_dense.union(other), + } + } + + fn subtract(&mut self, other: &HybridBitSet<T>) -> bool { + assert_eq!(self.domain_size(), other.domain_size()); + match self { + HybridBitSet::Sparse(self_sparse) => { + sequential_update(|elem| self_sparse.remove(elem), other.iter()) + } + HybridBitSet::Dense(self_dense) => self_dense.subtract(other), + } + } + + fn intersect(&mut self, other: &HybridBitSet<T>) -> bool { + assert_eq!(self.domain_size(), other.domain_size()); + match self { + HybridBitSet::Sparse(self_sparse) => { + sparse_intersect(self_sparse, |elem| other.contains(*elem)) + } + HybridBitSet::Dense(self_dense) => match other { + HybridBitSet::Sparse(other_sparse) => { + let (updated, changed) = dense_sparse_intersect(self_dense, other_sparse); + *self = HybridBitSet::Sparse(updated); + changed + } + HybridBitSet::Dense(other_dense) => self_dense.intersect(other_dense), + }, + } + } +} + +impl<T> Clone for BitSet<T> { + fn clone(&self) -> Self { + BitSet { domain_size: self.domain_size, words: self.words.clone(), marker: PhantomData } + } + + fn clone_from(&mut self, from: &Self) { + self.domain_size = from.domain_size; + self.words.clone_from(&from.words); + } +} + +impl<T: Idx> fmt::Debug for BitSet<T> { + fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result { + w.debug_list().entries(self.iter()).finish() + } +} + +impl<T: Idx> ToString for BitSet<T> { + fn to_string(&self) -> String { + let mut result = String::new(); + let mut sep = '['; + + // Note: this is a little endian printout of bytes. + + // i tracks how many bits we have printed so far. + let mut i = 0; + for word in &self.words { + let mut word = *word; + for _ in 0..WORD_BYTES { + // for each byte in `word`: + let remain = self.domain_size - i; + // If less than a byte remains, then mask just that many bits. + let mask = if remain <= 8 { (1 << remain) - 1 } else { 0xFF }; + assert!(mask <= 0xFF); + let byte = word & mask; + + result.push_str(&format!("{}{:02x}", sep, byte)); + + if remain <= 8 { + break; + } + word >>= 8; + i += 8; + sep = '-'; + } + sep = '|'; + } + result.push(']'); + + result + } +} + +pub struct BitIter<'a, T: Idx> { + /// A copy of the current word, but with any already-visited bits cleared. + /// (This lets us use `trailing_zeros()` to find the next set bit.) When it + /// is reduced to 0, we move onto the next word. + word: Word, + + /// The offset (measured in bits) of the current word. + offset: usize, + + /// Underlying iterator over the words. + iter: slice::Iter<'a, Word>, + + marker: PhantomData<T>, +} + +impl<'a, T: Idx> BitIter<'a, T> { + #[inline] + fn new(words: &'a [Word]) -> BitIter<'a, T> { + // We initialize `word` and `offset` to degenerate values. On the first + // call to `next()` we will fall through to getting the first word from + // `iter`, which sets `word` to the first word (if there is one) and + // `offset` to 0. Doing it this way saves us from having to maintain + // additional state about whether we have started. + BitIter { + word: 0, + offset: usize::MAX - (WORD_BITS - 1), + iter: words.iter(), + marker: PhantomData, + } + } +} + +impl<'a, T: Idx> Iterator for BitIter<'a, T> { + type Item = T; + fn next(&mut self) -> Option<T> { + loop { + if self.word != 0 { + // Get the position of the next set bit in the current word, + // then clear the bit. + let bit_pos = self.word.trailing_zeros() as usize; + let bit = 1 << bit_pos; + self.word ^= bit; + return Some(T::new(bit_pos + self.offset)); + } + + // Move onto the next word. `wrapping_add()` is needed to handle + // the degenerate initial value given to `offset` in `new()`. + let word = self.iter.next()?; + self.word = *word; + self.offset = self.offset.wrapping_add(WORD_BITS); + } + } +} + +#[inline] +fn bitwise<Op>(out_vec: &mut [Word], in_vec: &[Word], op: Op) -> bool +where + Op: Fn(Word, Word) -> Word, +{ + assert_eq!(out_vec.len(), in_vec.len()); + let mut changed = 0; + for (out_elem, in_elem) in iter::zip(out_vec, in_vec) { + let old_val = *out_elem; + let new_val = op(old_val, *in_elem); + *out_elem = new_val; + // This is essentially equivalent to a != with changed being a bool, but + // in practice this code gets auto-vectorized by the compiler for most + // operators. Using != here causes us to generate quite poor code as the + // compiler tries to go back to a boolean on each loop iteration. + changed |= old_val ^ new_val; + } + changed != 0 +} + +/// Does this bitwise operation change `out_vec`? +#[inline] +fn bitwise_changes<Op>(out_vec: &[Word], in_vec: &[Word], op: Op) -> bool +where + Op: Fn(Word, Word) -> Word, +{ + assert_eq!(out_vec.len(), in_vec.len()); + for (out_elem, in_elem) in iter::zip(out_vec, in_vec) { + let old_val = *out_elem; + let new_val = op(old_val, *in_elem); + if old_val != new_val { + return true; + } + } + false +} + +const SPARSE_MAX: usize = 8; + +/// A fixed-size bitset type with a sparse representation and a maximum of +/// `SPARSE_MAX` elements. The elements are stored as a sorted `ArrayVec` with +/// no duplicates. +/// +/// This type is used by `HybridBitSet`; do not use directly. +#[derive(Clone, Debug)] +pub struct SparseBitSet<T> { + domain_size: usize, + elems: ArrayVec<T, SPARSE_MAX>, +} + +impl<T: Idx> SparseBitSet<T> { + fn new_empty(domain_size: usize) -> Self { + SparseBitSet { domain_size, elems: ArrayVec::new() } + } + + fn len(&self) -> usize { + self.elems.len() + } + + fn is_empty(&self) -> bool { + self.elems.len() == 0 + } + + fn contains(&self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + self.elems.contains(&elem) + } + + fn insert(&mut self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + let changed = if let Some(i) = self.elems.iter().position(|&e| e.index() >= elem.index()) { + if self.elems[i] == elem { + // `elem` is already in the set. + false + } else { + // `elem` is smaller than one or more existing elements. + self.elems.insert(i, elem); + true + } + } else { + // `elem` is larger than all existing elements. + self.elems.push(elem); + true + }; + assert!(self.len() <= SPARSE_MAX); + changed + } + + fn remove(&mut self, elem: T) -> bool { + assert!(elem.index() < self.domain_size); + if let Some(i) = self.elems.iter().position(|&e| e == elem) { + self.elems.remove(i); + true + } else { + false + } + } + + fn to_dense(&self) -> BitSet<T> { + let mut dense = BitSet::new_empty(self.domain_size); + for elem in self.elems.iter() { + dense.insert(*elem); + } + dense + } + + fn iter(&self) -> slice::Iter<'_, T> { + self.elems.iter() + } + + bit_relations_inherent_impls! {} +} + +impl<T: Idx + Ord> SparseBitSet<T> { + fn last_set_in(&self, range: impl RangeBounds<T>) -> Option<T> { + let mut last_leq = None; + for e in self.iter() { + if range.contains(e) { + last_leq = Some(*e); + } + } + last_leq + } +} + +/// A fixed-size bitset type with a hybrid representation: sparse when there +/// are up to a `SPARSE_MAX` elements in the set, but dense when there are more +/// than `SPARSE_MAX`. +/// +/// This type is especially efficient for sets that typically have a small +/// number of elements, but a large `domain_size`, and are cleared frequently. +/// +/// `T` is an index type, typically a newtyped `usize` wrapper, but it can also +/// just be `usize`. +/// +/// All operations that involve an element will panic if the element is equal +/// to or greater than the domain size. All operations that involve two bitsets +/// will panic if the bitsets have differing domain sizes. +#[derive(Clone)] +pub enum HybridBitSet<T> { + Sparse(SparseBitSet<T>), + Dense(BitSet<T>), +} + +impl<T: Idx> fmt::Debug for HybridBitSet<T> { + fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result { + match self { + Self::Sparse(b) => b.fmt(w), + Self::Dense(b) => b.fmt(w), + } + } +} + +impl<T: Idx> HybridBitSet<T> { + pub fn new_empty(domain_size: usize) -> Self { + HybridBitSet::Sparse(SparseBitSet::new_empty(domain_size)) + } + + pub fn domain_size(&self) -> usize { + match self { + HybridBitSet::Sparse(sparse) => sparse.domain_size, + HybridBitSet::Dense(dense) => dense.domain_size, + } + } + + pub fn clear(&mut self) { + let domain_size = self.domain_size(); + *self = HybridBitSet::new_empty(domain_size); + } + + pub fn contains(&self, elem: T) -> bool { + match self { + HybridBitSet::Sparse(sparse) => sparse.contains(elem), + HybridBitSet::Dense(dense) => dense.contains(elem), + } + } + + pub fn superset(&self, other: &HybridBitSet<T>) -> bool { + match (self, other) { + (HybridBitSet::Dense(self_dense), HybridBitSet::Dense(other_dense)) => { + self_dense.superset(other_dense) + } + _ => { + assert!(self.domain_size() == other.domain_size()); + other.iter().all(|elem| self.contains(elem)) + } + } + } + + pub fn is_empty(&self) -> bool { + match self { + HybridBitSet::Sparse(sparse) => sparse.is_empty(), + HybridBitSet::Dense(dense) => dense.is_empty(), + } + } + + /// Returns the previous element present in the bitset from `elem`, + /// inclusively of elem. That is, will return `Some(elem)` if elem is in the + /// bitset. + pub fn last_set_in(&self, range: impl RangeBounds<T>) -> Option<T> + where + T: Ord, + { + match self { + HybridBitSet::Sparse(sparse) => sparse.last_set_in(range), + HybridBitSet::Dense(dense) => dense.last_set_in(range), + } + } + + pub fn insert(&mut self, elem: T) -> bool { + // No need to check `elem` against `self.domain_size` here because all + // the match cases check it, one way or another. + match self { + HybridBitSet::Sparse(sparse) if sparse.len() < SPARSE_MAX => { + // The set is sparse and has space for `elem`. + sparse.insert(elem) + } + HybridBitSet::Sparse(sparse) if sparse.contains(elem) => { + // The set is sparse and does not have space for `elem`, but + // that doesn't matter because `elem` is already present. + false + } + HybridBitSet::Sparse(sparse) => { + // The set is sparse and full. Convert to a dense set. + let mut dense = sparse.to_dense(); + let changed = dense.insert(elem); + assert!(changed); + *self = HybridBitSet::Dense(dense); + changed + } + HybridBitSet::Dense(dense) => dense.insert(elem), + } + } + + pub fn insert_range(&mut self, elems: impl RangeBounds<T>) { + // No need to check `elem` against `self.domain_size` here because all + // the match cases check it, one way or another. + let start = match elems.start_bound().cloned() { + Bound::Included(start) => start.index(), + Bound::Excluded(start) => start.index() + 1, + Bound::Unbounded => 0, + }; + let end = match elems.end_bound().cloned() { + Bound::Included(end) => end.index() + 1, + Bound::Excluded(end) => end.index(), + Bound::Unbounded => self.domain_size() - 1, + }; + let Some(len) = end.checked_sub(start) else { return }; + match self { + HybridBitSet::Sparse(sparse) if sparse.len() + len < SPARSE_MAX => { + // The set is sparse and has space for `elems`. + for elem in start..end { + sparse.insert(T::new(elem)); + } + } + HybridBitSet::Sparse(sparse) => { + // The set is sparse and full. Convert to a dense set. + let mut dense = sparse.to_dense(); + dense.insert_range(elems); + *self = HybridBitSet::Dense(dense); + } + HybridBitSet::Dense(dense) => dense.insert_range(elems), + } + } + + pub fn insert_all(&mut self) { + let domain_size = self.domain_size(); + match self { + HybridBitSet::Sparse(_) => { + *self = HybridBitSet::Dense(BitSet::new_filled(domain_size)); + } + HybridBitSet::Dense(dense) => dense.insert_all(), + } + } + + pub fn remove(&mut self, elem: T) -> bool { + // Note: we currently don't bother going from Dense back to Sparse. + match self { + HybridBitSet::Sparse(sparse) => sparse.remove(elem), + HybridBitSet::Dense(dense) => dense.remove(elem), + } + } + + /// Converts to a dense set, consuming itself in the process. + pub fn to_dense(self) -> BitSet<T> { + match self { + HybridBitSet::Sparse(sparse) => sparse.to_dense(), + HybridBitSet::Dense(dense) => dense, + } + } + + pub fn iter(&self) -> HybridIter<'_, T> { + match self { + HybridBitSet::Sparse(sparse) => HybridIter::Sparse(sparse.iter()), + HybridBitSet::Dense(dense) => HybridIter::Dense(dense.iter()), + } + } + + bit_relations_inherent_impls! {} +} + +pub enum HybridIter<'a, T: Idx> { + Sparse(slice::Iter<'a, T>), + Dense(BitIter<'a, T>), +} + +impl<'a, T: Idx> Iterator for HybridIter<'a, T> { + type Item = T; + + fn next(&mut self) -> Option<T> { + match self { + HybridIter::Sparse(sparse) => sparse.next().copied(), + HybridIter::Dense(dense) => dense.next(), + } + } +} + +/// A resizable bitset type with a dense representation. +/// +/// `T` is an index type, typically a newtyped `usize` wrapper, but it can also +/// just be `usize`. +/// +/// All operations that involve an element will panic if the element is equal +/// to or greater than the domain size. +#[derive(Clone, Debug, PartialEq)] +pub struct GrowableBitSet<T: Idx> { + bit_set: BitSet<T>, +} + +impl<T: Idx> Default for GrowableBitSet<T> { + fn default() -> Self { + GrowableBitSet::new_empty() + } +} + +impl<T: Idx> GrowableBitSet<T> { + /// Ensure that the set can hold at least `min_domain_size` elements. + pub fn ensure(&mut self, min_domain_size: usize) { + if self.bit_set.domain_size < min_domain_size { + self.bit_set.domain_size = min_domain_size; + } + + let min_num_words = num_words(min_domain_size); + if self.bit_set.words.len() < min_num_words { + self.bit_set.words.resize(min_num_words, 0) + } + } + + pub fn new_empty() -> GrowableBitSet<T> { + GrowableBitSet { bit_set: BitSet::new_empty(0) } + } + + pub fn with_capacity(capacity: usize) -> GrowableBitSet<T> { + GrowableBitSet { bit_set: BitSet::new_empty(capacity) } + } + + /// Returns `true` if the set has changed. + #[inline] + pub fn insert(&mut self, elem: T) -> bool { + self.ensure(elem.index() + 1); + self.bit_set.insert(elem) + } + + /// Returns `true` if the set has changed. + #[inline] + pub fn remove(&mut self, elem: T) -> bool { + self.ensure(elem.index() + 1); + self.bit_set.remove(elem) + } + + #[inline] + pub fn is_empty(&self) -> bool { + self.bit_set.is_empty() + } + + #[inline] + pub fn contains(&self, elem: T) -> bool { + let (word_index, mask) = word_index_and_mask(elem); + self.bit_set.words.get(word_index).map_or(false, |word| (word & mask) != 0) + } + + #[inline] + pub fn iter(&self) -> BitIter<'_, T> { + self.bit_set.iter() + } + + #[inline] + pub fn len(&self) -> usize { + self.bit_set.count() + } +} + +impl<T: Idx> From<BitSet<T>> for GrowableBitSet<T> { + fn from(bit_set: BitSet<T>) -> Self { + Self { bit_set } + } +} + +/// A fixed-size 2D bit matrix type with a dense representation. +/// +/// `R` and `C` are index types used to identify rows and columns respectively; +/// typically newtyped `usize` wrappers, but they can also just be `usize`. +/// +/// All operations that involve a row and/or column index will panic if the +/// index exceeds the relevant bound. +#[derive(Clone, Eq, PartialEq, Hash, Decodable, Encodable)] +pub struct BitMatrix<R: Idx, C: Idx> { + num_rows: usize, + num_columns: usize, + words: Vec<Word>, + marker: PhantomData<(R, C)>, +} + +impl<R: Idx, C: Idx> BitMatrix<R, C> { + /// Creates a new `rows x columns` matrix, initially empty. + pub fn new(num_rows: usize, num_columns: usize) -> BitMatrix<R, C> { + // For every element, we need one bit for every other + // element. Round up to an even number of words. + let words_per_row = num_words(num_columns); + BitMatrix { + num_rows, + num_columns, + words: vec![0; num_rows * words_per_row], + marker: PhantomData, + } + } + + /// Creates a new matrix, with `row` used as the value for every row. + pub fn from_row_n(row: &BitSet<C>, num_rows: usize) -> BitMatrix<R, C> { + let num_columns = row.domain_size(); + let words_per_row = num_words(num_columns); + assert_eq!(words_per_row, row.words().len()); + BitMatrix { + num_rows, + num_columns, + words: iter::repeat(row.words()).take(num_rows).flatten().cloned().collect(), + marker: PhantomData, + } + } + + pub fn rows(&self) -> impl Iterator<Item = R> { + (0..self.num_rows).map(R::new) + } + + /// The range of bits for a given row. + fn range(&self, row: R) -> (usize, usize) { + let words_per_row = num_words(self.num_columns); + let start = row.index() * words_per_row; + (start, start + words_per_row) + } + + /// Sets the cell at `(row, column)` to true. Put another way, insert + /// `column` to the bitset for `row`. + /// + /// Returns `true` if this changed the matrix. + pub fn insert(&mut self, row: R, column: C) -> bool { + assert!(row.index() < self.num_rows && column.index() < self.num_columns); + let (start, _) = self.range(row); + let (word_index, mask) = word_index_and_mask(column); + let words = &mut self.words[..]; + let word = words[start + word_index]; + let new_word = word | mask; + words[start + word_index] = new_word; + word != new_word + } + + /// Do the bits from `row` contain `column`? Put another way, is + /// the matrix cell at `(row, column)` true? Put yet another way, + /// if the matrix represents (transitive) reachability, can + /// `row` reach `column`? + pub fn contains(&self, row: R, column: C) -> bool { + assert!(row.index() < self.num_rows && column.index() < self.num_columns); + let (start, _) = self.range(row); + let (word_index, mask) = word_index_and_mask(column); + (self.words[start + word_index] & mask) != 0 + } + + /// Returns those indices that are true in rows `a` and `b`. This + /// is an *O*(*n*) operation where *n* is the number of elements + /// (somewhat independent from the actual size of the + /// intersection, in particular). + pub fn intersect_rows(&self, row1: R, row2: R) -> Vec<C> { + assert!(row1.index() < self.num_rows && row2.index() < self.num_rows); + let (row1_start, row1_end) = self.range(row1); + let (row2_start, row2_end) = self.range(row2); + let mut result = Vec::with_capacity(self.num_columns); + for (base, (i, j)) in (row1_start..row1_end).zip(row2_start..row2_end).enumerate() { + let mut v = self.words[i] & self.words[j]; + for bit in 0..WORD_BITS { + if v == 0 { + break; + } + if v & 0x1 != 0 { + result.push(C::new(base * WORD_BITS + bit)); + } + v >>= 1; + } + } + result + } + + /// Adds the bits from row `read` to the bits from row `write`, and + /// returns `true` if anything changed. + /// + /// This is used when computing transitive reachability because if + /// you have an edge `write -> read`, because in that case + /// `write` can reach everything that `read` can (and + /// potentially more). + pub fn union_rows(&mut self, read: R, write: R) -> bool { + assert!(read.index() < self.num_rows && write.index() < self.num_rows); + let (read_start, read_end) = self.range(read); + let (write_start, write_end) = self.range(write); + let words = &mut self.words[..]; + let mut changed = false; + for (read_index, write_index) in iter::zip(read_start..read_end, write_start..write_end) { + let word = words[write_index]; + let new_word = word | words[read_index]; + words[write_index] = new_word; + changed |= word != new_word; + } + changed + } + + /// Adds the bits from `with` to the bits from row `write`, and + /// returns `true` if anything changed. + pub fn union_row_with(&mut self, with: &BitSet<C>, write: R) -> bool { + assert!(write.index() < self.num_rows); + assert_eq!(with.domain_size(), self.num_columns); + let (write_start, write_end) = self.range(write); + let mut changed = false; + for (read_index, write_index) in iter::zip(0..with.words().len(), write_start..write_end) { + let word = self.words[write_index]; + let new_word = word | with.words()[read_index]; + self.words[write_index] = new_word; + changed |= word != new_word; + } + changed + } + + /// Sets every cell in `row` to true. + pub fn insert_all_into_row(&mut self, row: R) { + assert!(row.index() < self.num_rows); + let (start, end) = self.range(row); + let words = &mut self.words[..]; + for index in start..end { + words[index] = !0; + } + clear_excess_bits_in_final_word(self.num_columns, &mut self.words[..end]); + } + + /// Gets a slice of the underlying words. + pub fn words(&self) -> &[Word] { + &self.words + } + + /// Iterates through all the columns set to true in a given row of + /// the matrix. + pub fn iter(&self, row: R) -> BitIter<'_, C> { + assert!(row.index() < self.num_rows); + let (start, end) = self.range(row); + BitIter::new(&self.words[start..end]) + } + + /// Returns the number of elements in `row`. + pub fn count(&self, row: R) -> usize { + let (start, end) = self.range(row); + self.words[start..end].iter().map(|e| e.count_ones() as usize).sum() + } +} + +impl<R: Idx, C: Idx> fmt::Debug for BitMatrix<R, C> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + /// Forces its contents to print in regular mode instead of alternate mode. + struct OneLinePrinter<T>(T); + impl<T: fmt::Debug> fmt::Debug for OneLinePrinter<T> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(fmt, "{:?}", self.0) + } + } + + write!(fmt, "BitMatrix({}x{}) ", self.num_rows, self.num_columns)?; + let items = self.rows().flat_map(|r| self.iter(r).map(move |c| (r, c))); + fmt.debug_set().entries(items.map(OneLinePrinter)).finish() + } +} + +/// A fixed-column-size, variable-row-size 2D bit matrix with a moderately +/// sparse representation. +/// +/// Initially, every row has no explicit representation. If any bit within a +/// row is set, the entire row is instantiated as `Some(<HybridBitSet>)`. +/// Furthermore, any previously uninstantiated rows prior to it will be +/// instantiated as `None`. Those prior rows may themselves become fully +/// instantiated later on if any of their bits are set. +/// +/// `R` and `C` are index types used to identify rows and columns respectively; +/// typically newtyped `usize` wrappers, but they can also just be `usize`. +#[derive(Clone, Debug)] +pub struct SparseBitMatrix<R, C> +where + R: Idx, + C: Idx, +{ + num_columns: usize, + rows: IndexVec<R, Option<HybridBitSet<C>>>, +} + +impl<R: Idx, C: Idx> SparseBitMatrix<R, C> { + /// Creates a new empty sparse bit matrix with no rows or columns. + pub fn new(num_columns: usize) -> Self { + Self { num_columns, rows: IndexVec::new() } + } + + fn ensure_row(&mut self, row: R) -> &mut HybridBitSet<C> { + // Instantiate any missing rows up to and including row `row` with an empty HybridBitSet. + // Then replace row `row` with a full HybridBitSet if necessary. + self.rows.get_or_insert_with(row, || HybridBitSet::new_empty(self.num_columns)) + } + + /// Sets the cell at `(row, column)` to true. Put another way, insert + /// `column` to the bitset for `row`. + /// + /// Returns `true` if this changed the matrix. + pub fn insert(&mut self, row: R, column: C) -> bool { + self.ensure_row(row).insert(column) + } + + /// Sets the cell at `(row, column)` to false. Put another way, delete + /// `column` from the bitset for `row`. Has no effect if `row` does not + /// exist. + /// + /// Returns `true` if this changed the matrix. + pub fn remove(&mut self, row: R, column: C) -> bool { + match self.rows.get_mut(row) { + Some(Some(row)) => row.remove(column), + _ => false, + } + } + + /// Sets all columns at `row` to false. Has no effect if `row` does + /// not exist. + pub fn clear(&mut self, row: R) { + if let Some(Some(row)) = self.rows.get_mut(row) { + row.clear(); + } + } + + /// Do the bits from `row` contain `column`? Put another way, is + /// the matrix cell at `(row, column)` true? Put yet another way, + /// if the matrix represents (transitive) reachability, can + /// `row` reach `column`? + pub fn contains(&self, row: R, column: C) -> bool { + self.row(row).map_or(false, |r| r.contains(column)) + } + + /// Adds the bits from row `read` to the bits from row `write`, and + /// returns `true` if anything changed. + /// + /// This is used when computing transitive reachability because if + /// you have an edge `write -> read`, because in that case + /// `write` can reach everything that `read` can (and + /// potentially more). + pub fn union_rows(&mut self, read: R, write: R) -> bool { + if read == write || self.row(read).is_none() { + return false; + } + + self.ensure_row(write); + if let (Some(read_row), Some(write_row)) = self.rows.pick2_mut(read, write) { + write_row.union(read_row) + } else { + unreachable!() + } + } + + /// Insert all bits in the given row. + pub fn insert_all_into_row(&mut self, row: R) { + self.ensure_row(row).insert_all(); + } + + pub fn rows(&self) -> impl Iterator<Item = R> { + self.rows.indices() + } + + /// Iterates through all the columns set to true in a given row of + /// the matrix. + pub fn iter<'a>(&'a self, row: R) -> impl Iterator<Item = C> + 'a { + self.row(row).into_iter().flat_map(|r| r.iter()) + } + + pub fn row(&self, row: R) -> Option<&HybridBitSet<C>> { + self.rows.get(row)?.as_ref() + } + + /// Intersects `row` with `set`. `set` can be either `BitSet` or + /// `HybridBitSet`. Has no effect if `row` does not exist. + /// + /// Returns true if the row was changed. + pub fn intersect_row<Set>(&mut self, row: R, set: &Set) -> bool + where + HybridBitSet<C>: BitRelations<Set>, + { + match self.rows.get_mut(row) { + Some(Some(row)) => row.intersect(set), + _ => false, + } + } + + /// Subtracts `set from `row`. `set` can be either `BitSet` or + /// `HybridBitSet`. Has no effect if `row` does not exist. + /// + /// Returns true if the row was changed. + pub fn subtract_row<Set>(&mut self, row: R, set: &Set) -> bool + where + HybridBitSet<C>: BitRelations<Set>, + { + match self.rows.get_mut(row) { + Some(Some(row)) => row.subtract(set), + _ => false, + } + } + + /// Unions `row` with `set`. `set` can be either `BitSet` or + /// `HybridBitSet`. + /// + /// Returns true if the row was changed. + pub fn union_row<Set>(&mut self, row: R, set: &Set) -> bool + where + HybridBitSet<C>: BitRelations<Set>, + { + self.ensure_row(row).union(set) + } +} + +#[inline] +fn num_words<T: Idx>(domain_size: T) -> usize { + (domain_size.index() + WORD_BITS - 1) / WORD_BITS +} + +#[inline] +fn num_chunks<T: Idx>(domain_size: T) -> usize { + assert!(domain_size.index() > 0); + (domain_size.index() + CHUNK_BITS - 1) / CHUNK_BITS +} + +#[inline] +fn word_index_and_mask<T: Idx>(elem: T) -> (usize, Word) { + let elem = elem.index(); + let word_index = elem / WORD_BITS; + let mask = 1 << (elem % WORD_BITS); + (word_index, mask) +} + +#[inline] +fn chunk_index<T: Idx>(elem: T) -> usize { + elem.index() / CHUNK_BITS +} + +#[inline] +fn chunk_word_index_and_mask<T: Idx>(elem: T) -> (usize, Word) { + let chunk_elem = elem.index() % CHUNK_BITS; + word_index_and_mask(chunk_elem) +} + +fn clear_excess_bits_in_final_word(domain_size: usize, words: &mut [Word]) { + let num_bits_in_final_word = domain_size % WORD_BITS; + if num_bits_in_final_word > 0 { + let mask = (1 << num_bits_in_final_word) - 1; + words[words.len() - 1] &= mask; + } +} + +#[inline] +fn max_bit(word: Word) -> usize { + WORD_BITS - 1 - word.leading_zeros() as usize +} + +/// Integral type used to represent the bit set. +pub trait FiniteBitSetTy: + BitAnd<Output = Self> + + BitAndAssign + + BitOrAssign + + Clone + + Copy + + Shl + + Not<Output = Self> + + PartialEq + + Sized +{ + /// Size of the domain representable by this type, e.g. 64 for `u64`. + const DOMAIN_SIZE: u32; + + /// Value which represents the `FiniteBitSet` having every bit set. + const FILLED: Self; + /// Value which represents the `FiniteBitSet` having no bits set. + const EMPTY: Self; + + /// Value for one as the integral type. + const ONE: Self; + /// Value for zero as the integral type. + const ZERO: Self; + + /// Perform a checked left shift on the integral type. + fn checked_shl(self, rhs: u32) -> Option<Self>; + /// Perform a checked right shift on the integral type. + fn checked_shr(self, rhs: u32) -> Option<Self>; +} + +impl FiniteBitSetTy for u32 { + const DOMAIN_SIZE: u32 = 32; + + const FILLED: Self = Self::MAX; + const EMPTY: Self = Self::MIN; + + const ONE: Self = 1u32; + const ZERO: Self = 0u32; + + fn checked_shl(self, rhs: u32) -> Option<Self> { + self.checked_shl(rhs) + } + + fn checked_shr(self, rhs: u32) -> Option<Self> { + self.checked_shr(rhs) + } +} + +impl std::fmt::Debug for FiniteBitSet<u32> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "{:032b}", self.0) + } +} + +impl FiniteBitSetTy for u64 { + const DOMAIN_SIZE: u32 = 64; + + const FILLED: Self = Self::MAX; + const EMPTY: Self = Self::MIN; + + const ONE: Self = 1u64; + const ZERO: Self = 0u64; + + fn checked_shl(self, rhs: u32) -> Option<Self> { + self.checked_shl(rhs) + } + + fn checked_shr(self, rhs: u32) -> Option<Self> { + self.checked_shr(rhs) + } +} + +impl std::fmt::Debug for FiniteBitSet<u64> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "{:064b}", self.0) + } +} + +impl FiniteBitSetTy for u128 { + const DOMAIN_SIZE: u32 = 128; + + const FILLED: Self = Self::MAX; + const EMPTY: Self = Self::MIN; + + const ONE: Self = 1u128; + const ZERO: Self = 0u128; + + fn checked_shl(self, rhs: u32) -> Option<Self> { + self.checked_shl(rhs) + } + + fn checked_shr(self, rhs: u32) -> Option<Self> { + self.checked_shr(rhs) + } +} + +impl std::fmt::Debug for FiniteBitSet<u128> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "{:0128b}", self.0) + } +} + +/// A fixed-sized bitset type represented by an integer type. Indices outwith than the range +/// representable by `T` are considered set. +#[derive(Copy, Clone, Eq, PartialEq, Decodable, Encodable)] +pub struct FiniteBitSet<T: FiniteBitSetTy>(pub T); + +impl<T: FiniteBitSetTy> FiniteBitSet<T> { + /// Creates a new, empty bitset. + pub fn new_empty() -> Self { + Self(T::EMPTY) + } + + /// Sets the `index`th bit. + pub fn set(&mut self, index: u32) { + self.0 |= T::ONE.checked_shl(index).unwrap_or(T::ZERO); + } + + /// Unsets the `index`th bit. + pub fn clear(&mut self, index: u32) { + self.0 &= !T::ONE.checked_shl(index).unwrap_or(T::ZERO); + } + + /// Sets the `i`th to `j`th bits. + pub fn set_range(&mut self, range: Range<u32>) { + let bits = T::FILLED + .checked_shl(range.end - range.start) + .unwrap_or(T::ZERO) + .not() + .checked_shl(range.start) + .unwrap_or(T::ZERO); + self.0 |= bits; + } + + /// Is the set empty? + pub fn is_empty(&self) -> bool { + self.0 == T::EMPTY + } + + /// Returns the domain size of the bitset. + pub fn within_domain(&self, index: u32) -> bool { + index < T::DOMAIN_SIZE + } + + /// Returns if the `index`th bit is set. + pub fn contains(&self, index: u32) -> Option<bool> { + self.within_domain(index) + .then(|| ((self.0.checked_shr(index).unwrap_or(T::ONE)) & T::ONE) == T::ONE) + } +} + +impl<T: FiniteBitSetTy> Default for FiniteBitSet<T> { + fn default() -> Self { + Self::new_empty() + } +} |