rust/src/librustc_data_structures/bitvec.rs

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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::collections::BTreeMap;
use std::collections::btree_map::Entry;
use std::marker::PhantomData;
use std::iter::FromIterator;
use indexed_vec::{Idx, IndexVec};
type Word = u128;
const WORD_BITS: usize = 128;
/// A very simple BitVector type.
#[derive(Clone, Debug, PartialEq)]
pub struct BitVector {
data: Vec<Word>,
}
impl BitVector {
#[inline]
pub fn new(num_bits: usize) -> BitVector {
let num_words = words(num_bits);
BitVector {
data: vec![0; num_words],
}
}
#[inline]
pub fn clear(&mut self) {
for p in &mut self.data {
*p = 0;
}
}
pub fn count(&self) -> usize {
self.data.iter().map(|e| e.count_ones() as usize).sum()
}
#[inline]
pub fn contains(&self, bit: usize) -> bool {
let (word, mask) = word_mask(bit);
(self.data[word] & mask) != 0
}
/// Returns true if the bit has changed.
#[inline]
pub fn insert(&mut self, bit: usize) -> bool {
let (word, mask) = word_mask(bit);
let data = &mut self.data[word];
let value = *data;
let new_value = value | mask;
*data = new_value;
new_value != value
}
/// Returns true if the bit has changed.
#[inline]
pub fn remove(&mut self, bit: usize) -> bool {
let (word, mask) = word_mask(bit);
let data = &mut self.data[word];
let value = *data;
let new_value = value & !mask;
*data = new_value;
new_value != value
}
#[inline]
pub fn insert_all(&mut self, all: &BitVector) -> bool {
assert!(self.data.len() == all.data.len());
let mut changed = false;
for (i, j) in self.data.iter_mut().zip(&all.data) {
let value = *i;
*i = value | *j;
if value != *i {
changed = true;
}
}
changed
}
#[inline]
pub fn grow(&mut self, num_bits: usize) {
let num_words = words(num_bits);
if self.data.len() < num_words {
self.data.resize(num_words, 0)
}
}
/// Iterates over indexes of set bits in a sorted order
#[inline]
pub fn iter<'a>(&'a self) -> BitVectorIter<'a> {
BitVectorIter {
iter: self.data.iter(),
current: 0,
idx: 0,
}
}
}
pub struct BitVectorIter<'a> {
iter: ::std::slice::Iter<'a, Word>,
current: Word,
idx: usize,
}
impl<'a> Iterator for BitVectorIter<'a> {
type Item = usize;
fn next(&mut self) -> Option<usize> {
while self.current == 0 {
self.current = if let Some(&i) = self.iter.next() {
if i == 0 {
self.idx += WORD_BITS;
continue;
} else {
self.idx = words(self.idx) * WORD_BITS;
i
}
} else {
return None;
}
}
let offset = self.current.trailing_zeros() as usize;
self.current >>= offset;
self.current >>= 1; // shift otherwise overflows for 0b1000_0000_…_0000
self.idx += offset + 1;
return Some(self.idx - 1);
}
}
impl FromIterator<bool> for BitVector {
fn from_iter<I>(iter: I) -> BitVector
where
I: IntoIterator<Item = bool>,
{
let iter = iter.into_iter();
let (len, _) = iter.size_hint();
// Make the minimum length for the bitvector WORD_BITS bits since that's
// the smallest non-zero size anyway.
let len = if len < WORD_BITS { WORD_BITS } else { len };
let mut bv = BitVector::new(len);
for (idx, val) in iter.enumerate() {
if idx > len {
bv.grow(idx);
}
if val {
bv.insert(idx);
}
}
bv
}
}
/// A "bit matrix" is basically a matrix of booleans represented as
/// one gigantic bitvector. In other words, it is as if you have
/// `rows` bitvectors, each of length `columns`.
#[derive(Clone, Debug)]
pub struct BitMatrix {
columns: usize,
vector: Vec<Word>,
}
impl BitMatrix {
/// Create a new `rows x columns` matrix, initially empty.
pub fn new(rows: usize, columns: usize) -> BitMatrix {
// For every element, we need one bit for every other
// element. Round up to an even number of words.
let words_per_row = words(columns);
BitMatrix {
columns,
vector: vec![0; rows * words_per_row],
}
}
/// The range of bits for a given row.
fn range(&self, row: usize) -> (usize, usize) {
let words_per_row = words(self.columns);
let start = row * words_per_row;
(start, start + words_per_row)
}
/// Sets the cell at `(row, column)` to true. Put another way, add
/// `column` to the bitset for `row`.
///
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/// Returns true if this changed the matrix, and false otherwise.
pub fn add(&mut self, row: usize, column: usize) -> bool {
let (start, _) = self.range(row);
let (word, mask) = word_mask(column);
let vector = &mut self.vector[..];
let v1 = vector[start + word];
let v2 = v1 | mask;
vector[start + word] = v2;
v1 != v2
}
/// 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: usize, column: usize) -> bool {
let (start, _) = self.range(row);
let (word, mask) = word_mask(column);
(self.vector[start + word] & 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 intersection(&self, a: usize, b: usize) -> Vec<usize> {
let (a_start, a_end) = self.range(a);
let (b_start, b_end) = self.range(b);
let mut result = Vec::with_capacity(self.columns);
for (base, (i, j)) in (a_start..a_end).zip(b_start..b_end).enumerate() {
let mut v = self.vector[i] & self.vector[j];
for bit in 0..WORD_BITS {
if v == 0 {
break;
}
if v & 0x1 != 0 {
result.push(base * WORD_BITS + bit);
}
v >>= 1;
}
}
result
}
/// Add the bits from row `read` to the bits from row `write`,
/// return true if anything changed.
///
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/// 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).
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pub fn merge(&mut self, read: usize, write: usize) -> bool {
let (read_start, read_end) = self.range(read);
let (write_start, write_end) = self.range(write);
let vector = &mut self.vector[..];
let mut changed = false;
for (read_index, write_index) in (read_start..read_end).zip(write_start..write_end) {
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let v1 = vector[write_index];
let v2 = v1 | vector[read_index];
vector[write_index] = v2;
changed = changed | (v1 != v2);
}
changed
}
/// Iterates through all the columns set to true in a given row of
/// the matrix.
pub fn iter<'a>(&'a self, row: usize) -> BitVectorIter<'a> {
let (start, end) = self.range(row);
BitVectorIter {
iter: self.vector[start..end].iter(),
current: 0,
idx: 0,
}
}
}
#[derive(Clone, Debug)]
pub struct SparseBitMatrix<R, C>
where
R: Idx,
C: Idx,
{
vector: IndexVec<R, SparseBitSet<C>>,
}
impl<R: Idx, C: Idx> SparseBitMatrix<R, C> {
/// Create a new `rows x columns` matrix, initially empty.
pub fn new(rows: R, _columns: C) -> SparseBitMatrix<R, C> {
SparseBitMatrix {
vector: IndexVec::from_elem_n(SparseBitSet::new(), rows.index()),
}
}
/// 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, and false otherwise.
pub fn add(&mut self, row: R, column: C) -> bool {
self.vector[row].insert(column)
}
/// 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.vector[row].contains(column)
}
/// Add the bits from row `read` to the bits from row `write`,
/// return 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 merge(&mut self, read: R, write: R) -> bool {
let mut changed = false;
if read != write {
let (bit_set_read, bit_set_write) = self.vector.pick2_mut(read, write);
for read_val in bit_set_read.iter() {
changed = changed | bit_set_write.insert(read_val);
}
}
changed
}
/// 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.vector[row].iter()
}
}
#[derive(Clone, Debug)]
pub struct SparseBitSet<I: Idx> {
chunk_bits: BTreeMap<u32, Word>,
_marker: PhantomData<I>,
}
#[derive(Copy, Clone)]
pub struct SparseChunk<I> {
key: u32,
bits: Word,
_marker: PhantomData<I>,
}
impl<I: Idx> SparseChunk<I> {
pub fn one(index: I) -> Self {
let index = index.index();
let key_usize = index / 128;
let key = key_usize as u32;
assert_eq!(key as usize, key_usize);
SparseChunk {
key,
bits: 1 << (index % 128),
_marker: PhantomData,
}
}
pub fn any(&self) -> bool {
self.bits != 0
}
pub fn iter(&self) -> impl Iterator<Item = I> {
let base = self.key as usize * 128;
let mut bits = self.bits;
(0..128)
.map(move |i| {
let current_bits = bits;
bits >>= 1;
(i, current_bits)
})
.take_while(|&(_, bits)| bits != 0)
.filter_map(move |(i, bits)| {
if (bits & 1) != 0 {
Some(I::new(base + i))
} else {
None
}
})
}
}
impl<I: Idx> SparseBitSet<I> {
pub fn new() -> Self {
SparseBitSet {
chunk_bits: BTreeMap::new(),
_marker: PhantomData,
}
}
pub fn capacity(&self) -> usize {
self.chunk_bits.len() * 128
}
pub fn contains_chunk(&self, chunk: SparseChunk<I>) -> SparseChunk<I> {
SparseChunk {
bits: self.chunk_bits
.get(&chunk.key)
.map_or(0, |bits| bits & chunk.bits),
..chunk
}
}
pub fn insert_chunk(&mut self, chunk: SparseChunk<I>) -> SparseChunk<I> {
if chunk.bits == 0 {
return chunk;
}
let bits = self.chunk_bits.entry(chunk.key).or_insert(0);
let old_bits = *bits;
let new_bits = old_bits | chunk.bits;
*bits = new_bits;
let changed = new_bits ^ old_bits;
SparseChunk {
bits: changed,
..chunk
}
}
pub fn remove_chunk(&mut self, chunk: SparseChunk<I>) -> SparseChunk<I> {
if chunk.bits == 0 {
return chunk;
}
let changed = match self.chunk_bits.entry(chunk.key) {
Entry::Occupied(mut bits) => {
let old_bits = *bits.get();
let new_bits = old_bits & !chunk.bits;
if new_bits == 0 {
bits.remove();
} else {
bits.insert(new_bits);
}
new_bits ^ old_bits
}
Entry::Vacant(_) => 0,
};
SparseChunk {
bits: changed,
..chunk
}
}
pub fn clear(&mut self) {
self.chunk_bits.clear();
}
pub fn chunks<'a>(&'a self) -> impl Iterator<Item = SparseChunk<I>> + 'a {
self.chunk_bits.iter().map(|(&key, &bits)| SparseChunk {
key,
bits,
_marker: PhantomData,
})
}
pub fn contains(&self, index: I) -> bool {
self.contains_chunk(SparseChunk::one(index)).any()
}
pub fn insert(&mut self, index: I) -> bool {
self.insert_chunk(SparseChunk::one(index)).any()
}
pub fn remove(&mut self, index: I) -> bool {
self.remove_chunk(SparseChunk::one(index)).any()
}
pub fn iter<'a>(&'a self) -> impl Iterator<Item = I> + 'a {
self.chunks().flat_map(|chunk| chunk.iter())
}
}
#[inline]
fn words(elements: usize) -> usize {
(elements + WORD_BITS - 1) / WORD_BITS
}
#[inline]
fn word_mask(index: usize) -> (usize, Word) {
let word = index / WORD_BITS;
let mask = 1 << (index % WORD_BITS);
(word, mask)
}
#[test]
fn bitvec_iter_works() {
let mut bitvec = BitVector::new(100);
bitvec.insert(1);
bitvec.insert(10);
bitvec.insert(19);
bitvec.insert(62);
bitvec.insert(63);
bitvec.insert(64);
bitvec.insert(65);
bitvec.insert(66);
bitvec.insert(99);
assert_eq!(
bitvec.iter().collect::<Vec<_>>(),
[1, 10, 19, 62, 63, 64, 65, 66, 99]
);
}
#[test]
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fn bitvec_iter_works_2() {
let mut bitvec = BitVector::new(319);
bitvec.insert(0);
bitvec.insert(127);
bitvec.insert(191);
bitvec.insert(255);
bitvec.insert(319);
assert_eq!(bitvec.iter().collect::<Vec<_>>(), [0, 127, 191, 255, 319]);
}
#[test]
fn union_two_vecs() {
let mut vec1 = BitVector::new(65);
let mut vec2 = BitVector::new(65);
assert!(vec1.insert(3));
assert!(!vec1.insert(3));
assert!(vec2.insert(5));
assert!(vec2.insert(64));
assert!(vec1.insert_all(&vec2));
assert!(!vec1.insert_all(&vec2));
assert!(vec1.contains(3));
assert!(!vec1.contains(4));
assert!(vec1.contains(5));
assert!(!vec1.contains(63));
assert!(vec1.contains(64));
}
#[test]
fn grow() {
let mut vec1 = BitVector::new(65);
for index in 0..65 {
assert!(vec1.insert(index));
assert!(!vec1.insert(index));
}
vec1.grow(128);
// Check if the bits set before growing are still set
for index in 0..65 {
assert!(vec1.contains(index));
}
// Check if the new bits are all un-set
for index in 65..128 {
assert!(!vec1.contains(index));
}
// Check that we can set all new bits without running out of bounds
for index in 65..128 {
assert!(vec1.insert(index));
assert!(!vec1.insert(index));
}
}
#[test]
fn matrix_intersection() {
let mut vec1 = BitMatrix::new(200, 200);
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// (*) Elements reachable from both 2 and 65.
vec1.add(2, 3);
vec1.add(2, 6);
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vec1.add(2, 10); // (*)
vec1.add(2, 64); // (*)
vec1.add(2, 65);
vec1.add(2, 130);
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vec1.add(2, 160); // (*)
vec1.add(64, 133);
vec1.add(65, 2);
vec1.add(65, 8);
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vec1.add(65, 10); // (*)
vec1.add(65, 64); // (*)
vec1.add(65, 68);
vec1.add(65, 133);
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vec1.add(65, 160); // (*)
let intersection = vec1.intersection(2, 64);
assert!(intersection.is_empty());
let intersection = vec1.intersection(2, 65);
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assert_eq!(intersection, &[10, 64, 160]);
}
#[test]
fn matrix_iter() {
let mut matrix = BitMatrix::new(64, 100);
matrix.add(3, 22);
matrix.add(3, 75);
matrix.add(2, 99);
matrix.add(4, 0);
matrix.merge(3, 5);
let expected = [99];
let mut iter = expected.iter();
for i in matrix.iter(2) {
let j = *iter.next().unwrap();
assert_eq!(i, j);
}
assert!(iter.next().is_none());
let expected = [22, 75];
let mut iter = expected.iter();
for i in matrix.iter(3) {
let j = *iter.next().unwrap();
assert_eq!(i, j);
}
assert!(iter.next().is_none());
let expected = [0];
let mut iter = expected.iter();
for i in matrix.iter(4) {
let j = *iter.next().unwrap();
assert_eq!(i, j);
}
assert!(iter.next().is_none());
let expected = [22, 75];
let mut iter = expected.iter();
for i in matrix.iter(5) {
let j = *iter.next().unwrap();
assert_eq!(i, j);
}
assert!(iter.next().is_none());
}