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rust version: backtracking simplified and other improvements

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* backtracking: main loop simplified
* instead of the `fixed` Vec, we now use skip fields to calculate
  how many fields to skip in `next()` and `prev()`.
  This is faster because we get rid of the `if` statement
  thus no branching occurs.
This commit is contained in:
ddidderr 2023-03-21 18:17:34 +01:00
parent 198084206b
commit e446d9b74f
Signed by: ddidderr
GPG Key ID: 3841F1C27E6F0E14
4 changed files with 513 additions and 261 deletions
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3
.cargo/config.toml
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@ -1,3 +1,2 @@
[build]
target = "x86_64-unknown-linux-musl"
rustflags = "-C target-cpu=native -C strip=symbols"
rustflags = ["-C", "target-cpu=native", "-C", "target-feature=+crt-static"]

3
Cargo.toml
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@ -9,5 +9,6 @@ edition = "2021"
[profile.release]
lto = true
debug = false
codegen-units = 1
strip = true
panic = "abort"
codegen-units = 1

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350
src/main.rs
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@ -2,120 +2,89 @@ use std::time::Instant;
const BLOCK_SIZE: usize = 3;
const SIZE: usize = BLOCK_SIZE * BLOCK_SIZE;
const NUM_FIELDS: usize = SIZE * SIZE;
struct SField {
field: Vec<u8>,
fixed: Vec<bool>,
size: usize,
block_size: usize,
skipf: Vec<u8>,
skipb: Vec<u8>,
pos: usize,
pos_last_placed: usize,
num_fields: usize,
possible_values: Vec<Vec<u8>>,
}
/// Some test fields:
///
/// EMPTY FIELD
/// let field = vec![0; SIZE * SIZE];
///
/// MANY SOLUTIONS
/// #[rustfmt::skip]
/// let field = vec![
/// 0,0,0,0,0,0,0,0,9,
/// 0,0,0,0,8,9,0,2,0,
/// 0,0,0,0,2,0,4,0,0,
/// 0,0,4,0,6,0,0,0,8,
/// 0,0,0,5,0,0,0,0,0,
/// 0,6,5,0,0,2,0,7,4,
/// 0,3,0,0,0,5,0,4,0,
/// 0,0,1,8,0,0,0,0,0,
/// 0,0,8,2,0,0,0,6,0,
/// ];
///
/// HARD
/// #[rustfmt::skip]
/// let field = vec![
/// 8,4,0,0,6,0,5,0,1,
/// 0,0,0,0,0,3,0,4,0,
/// 0,0,6,9,0,0,0,0,7,
/// 0,2,0,7,1,0,0,0,6,
/// 0,0,0,6,3,0,0,0,0,
/// 9,0,0,0,0,0,0,5,0,
/// 0,0,0,0,4,0,0,6,0,
/// 2,0,0,0,0,0,1,8,0,
/// 0,0,5,0,0,0,3,0,0,
/// ];
///
/// EASY
/// #[rustfmt::skip]
/// let field = vec![
/// 5,9,0,6,1,3,0,0,0,
/// 0,0,0,9,0,0,5,0,0,
/// 8,0,3,0,5,7,6,4,0,
/// 0,7,5,0,0,0,4,0,6,
/// 0,6,0,7,4,0,2,0,8,
/// 2,0,8,0,0,0,7,5,3,
/// 0,0,0,5,6,1,0,7,0,
/// 0,0,1,0,7,0,9,0,0,
/// 7,3,6,0,2,0,0,0,0,
/// ];
///
/// // BLOCK_SIZE 4 MANY SOLUTIONS (DOESN'T FINISH)
/// #[rustfmt::skip]
/// let field = vec![
/// 0,15,0,0,0,0,11,4,0,5,0,0,0,0,12,8,
/// 12,0,0,9,0,1,0,5,0,0,8,15,0,0,0,13,
/// 0,0,3,0,0,10,13,0,0,11,4,0,15,0,6,0,
/// 13,10,0,11,0,0,0,14,0,3,2,0,0,9,0,0,
/// 0,0,15,10,8,0,0,0,0,0,14,0,0,6,2,0,
/// 0,0,14,0,0,0,6,0,0,0,0,0,1,0,0,0,
/// 0,11,0,8,3,0,15,1,6,0,0,0,0,0,0,7,
/// 0,6,0,7,0,0,0,0,8,13,0,0,10,0,0,0,
/// 0,14,0,2,0,0,0,0,3,0,5,0,11,15,9,0,
/// 0,0,0,12,11,0,2,0,0,0,0,0,0,0,0,0,
/// 0,8,0,0,6,14,1,0,13,15,0,0,0,0,0,10,
/// 10,0,0,3,9,0,7,0,0,1,0,0,13,12,8,0,
/// 7,0,0,0,0,0,14,0,0,0,0,0,0,0,0,9,
/// 0,3,0,14,0,0,9,6,0,0,0,0,0,4,0,0,
/// 0,4,6,0,0,7,0,0,0,0,0,0,0,0,0,0,
/// 5,2,0,0,0,4,10,15,1,0,3,0,0,0,7,0,
/// ];
impl SField {
pub fn new() -> SField {
let field = vec![0; SIZE * SIZE];
#[rustfmt::skip]
let field = vec![
0,0,0,0,0,0,0,0,0,
0,0,0,0,8,9,0,0,0,
0,0,0,0,2,0,4,0,0,
0,0,4,0,6,0,0,0,8,
0,0,0,5,0,0,0,0,0,
0,6,5,0,0,2,0,7,4,
0,3,0,0,0,5,0,4,0,
0,0,1,8,0,0,0,0,0,
0,0,8,2,0,0,0,6,0,
];
let mut fixed = Vec::with_capacity(SIZE * SIZE);
field.iter().for_each(|e| {
if *e == 0 {
fixed.push(false);
} else {
fixed.push(true);
fn find_fixed_streak_forward(mut idx: usize, field: &[u8]) -> u8 {
let mut fixed_count = 1;
idx += 1;
while idx < NUM_FIELDS && field[idx] > 0 {
fixed_count += 1;
idx += 1;
}
fixed_count
}
fn find_fixed_streak_backward(mut idx: usize, field: &[u8]) -> u8 {
let mut fixed_count = 1;
idx -= 1;
while idx < NUM_FIELDS && field[idx] > 0 {
fixed_count += 1;
idx -= 1;
}
fixed_count
}
let mut skipf = vec![0; NUM_FIELDS];
for (idx, nr) in field.iter().enumerate() {
match nr {
0 => skipf[idx] = *nr,
_ => skipf[idx] = find_fixed_streak_forward(idx, &field),
}
}
let mut skipb = vec![0; NUM_FIELDS];
for (idx, nr) in field.iter().enumerate().rev() {
match nr {
0 => skipb[idx] = *nr,
_ => skipb[idx] = find_fixed_streak_backward(idx, &field),
}
}
});
SField {
field,
fixed,
size: SIZE,
block_size: BLOCK_SIZE,
skipf,
skipb,
pos: 0,
pos_last_placed: 0,
num_fields: SIZE * SIZE,
possible_values: vec![vec![]; SIZE * SIZE],
}
}
fn build_possible_values_db(&mut self) {
for idx in 0..self.num_fields {
if self.fixed[idx] {
for idx in 0..NUM_FIELDS {
if self.field[idx] != 0 {
continue;
}
self.pos = idx;
// try all values between 1 and =self.size and remember the good ones
let mut good_ones = Vec::with_capacity(self.size);
for nr in 1..=(self.size as u8) {
let mut good_ones = Vec::with_capacity(SIZE);
for nr in 1..=(SIZE as u8) {
if self.ok(nr) {
good_ones.push(nr);
}
@ -126,121 +95,59 @@ impl SField {
}
pub fn solve_backtracking(&mut self) -> bool {
let mut found_solution = false;
let mut num_solutions = 0;
let mut last_num_solutions = num_solutions;
let mut loop_count = 0;
let mut last_loop_count = loop_count;
let mut now = Instant::now();
loop {
loop_count += 1;
const MILLIS_PER_SEC: u128 = 1_000;
const UPDATE_DELAY_MS: u128 = 80;
if loop_count % 1000 == 0 {
let elapsed_ms = now.elapsed().as_millis();
if elapsed_ms <= UPDATE_DELAY_MS {
continue;
}
self.print_clear();
self.print();
println!(
"{} loops/sec",
(loop_count - last_loop_count) * (MILLIS_PER_SEC / elapsed_ms)
);
println!(
"{} solutions/sec",
(num_solutions - last_num_solutions) * (MILLIS_PER_SEC / elapsed_ms)
);
last_loop_count = loop_count;
last_num_solutions = num_solutions;
now = Instant::now();
}
if self.is_end() {
found_solution = true;
num_solutions += 1;
/*
if num_solutions % 100 == 0 {
self.print_clear();
println!("Solutions: {}", num_solutions);
self.print();
}
*/
if self.is_fixed() {
continue;
}
self.clear_current_field();
self.prev();
self.goto_prev_free_field();
}
if self.is_fixed() {
self.next();
continue;
}
if self.goto_next_free_field() {
if self.put_valid_nr() {
self.next();
continue;
} else {
//println!("put_valid_nr failed for pos {}", self.pos);
//std::thread::sleep_ms(300);
if !self.put_valid_nr() {
self.clear_current_field();
if !self.prev() {
self.print_clear();
self.print();
println!("Number of solutions: {}", num_solutions);
break;
}
if !self.goto_prev_free_field() {
continue;
}
if !self.next() {
num_solutions += 1;
if num_solutions % 10_000 == 0 {
self.print_clear();
self.print();
println!("Number of solutions: {}", num_solutions);
break;
}
}
self.clear_current_field();
self.prev();
}
}
found_solution
num_solutions > 0
}
#[inline(always)]
fn print_gray(&self) {
print!("\x1b\x5b\x31\x3b\x33\x30\x6d");
}
#[inline(always)]
fn print_green(&self) {
print!("\x1b\x5b\x31\x3b\x33\x32\x6d");
}
#[inline(always)]
fn print_red(&self) {
print!("\x1b\x5b\x31\x3b\x33\x31\x6d");
}
#[inline(always)]
fn print_neutral(&self) {
print!("\x1b\x5b\x31\x3b\x30\x6d");
}
#[inline(always)]
fn print_clear(&self) {
print!("\x1b\x5b\x48\x1b\x5b\x32\x4a");
}
#[inline(always)]
fn print(&self) {
for i in 0..self.num_fields {
if i != 0 && i % self.size == 0 {
for i in 0..NUM_FIELDS {
if i != 0 && i % SIZE == 0 {
println!();
}
if i == self.pos_last_placed {
self.print_red();
} else if i == self.pos {
if i == self.pos {
self.print_green();
} else if self.get_field_at_pos(i) == 0 {
self.print_gray();
@ -248,57 +155,17 @@ impl SField {
print!("{:2} ", self.get_field_at_pos(i));
if i == self.pos || i == self.pos_last_placed || self.get_field_at_pos(i) == 0 {
if i == self.pos || self.get_field_at_pos(i) == 0 {
self.print_neutral();
}
}
println!();
}
#[inline(always)]
fn clear_current_field(&mut self) {
self.set(0);
}
#[inline(always)]
fn goto_prev_free_field(&mut self) -> bool {
while {
if !self.is_fixed() {
return true;
}
self.prev()
} {}
false
}
#[inline(always)]
fn goto_next_free_field(&mut self) -> bool {
while {
if !self.is_fixed() {
return true;
}
self.next()
} {}
false
}
#[inline(always)]
fn _put_valid_nr(&mut self) -> bool {
let current_nr = self.get_field_at_pos(self.pos);
for nr in current_nr..(self.size + 1) as u8 {
if self.ok(nr) {
self.set(nr);
return true;
}
}
false
}
#[inline(always)]
fn put_valid_nr(&mut self) -> bool {
let current_nr = self.get_field_at_pos(self.pos);
@ -320,32 +187,10 @@ impl SField {
false
}
#[inline(always)]
fn is_end(&self) -> bool {
!self.field.contains(&0)
}
#[inline(always)]
fn ok(&self, nr: u8) -> bool {
self.block_ok(nr) && self.row_ok(nr) && self.col_ok(nr)
}
#[inline(always)]
fn _pos_to_xy(&self) -> (usize, usize) {
let y = self.pos / self.size;
let x = self.pos % self.size;
(x + 1, y + 1)
}
#[inline(always)]
fn is_fixed(&self) -> bool {
// safety: self.pos can be used to index the field unchecked
// since the only methods modifying self.pos are
// `next()` and `prev()` and they do bounds checking
unsafe { *self.fixed.get_unchecked(self.pos) }
}
#[inline(always)]
fn get_field_at_pos(&self, pos: usize) -> u8 {
// safety:
// TODO
@ -354,81 +199,74 @@ impl SField {
unsafe { *self.field.get_unchecked(pos) }
}
#[inline(always)]
fn set(&mut self, nr: u8) {
self.field[self.pos] = nr;
self.pos_last_placed = self.pos;
}
#[inline(always)]
fn get_row(&self, row: &mut [u8; SIZE]) {
for (idx, row_elem) in row.iter_mut().enumerate() {
*row_elem = self.get_field_at_pos((self.pos / self.size) * self.size + idx);
*row_elem = self.get_field_at_pos((self.pos / SIZE) * SIZE + idx);
}
}
#[inline(always)]
fn get_col(&self, col: &mut [u8; SIZE]) {
for (idx, col_elem) in col.iter_mut().enumerate() {
*col_elem = self.get_field_at_pos(idx * self.size + self.pos % self.size);
*col_elem = self.get_field_at_pos(idx * SIZE + self.pos % SIZE);
}
}
#[inline(always)]
fn get_block(&self, block: &mut [u8; SIZE]) {
let block_start_row = self.pos / self.size / self.block_size * self.block_size;
let block_start_col = self.pos % self.size / self.block_size * self.block_size;
let block_start_row = self.pos / SIZE / BLOCK_SIZE * BLOCK_SIZE;
let block_start_col = self.pos % SIZE / BLOCK_SIZE * BLOCK_SIZE;
for r in 0..self.block_size {
for c in 0..self.block_size {
block[r * self.block_size + c] =
self.get_field_at_pos(self.size * (block_start_row + r) + block_start_col + c);
for r in 0..BLOCK_SIZE {
for c in 0..BLOCK_SIZE {
block[r * BLOCK_SIZE + c] =
self.get_field_at_pos(SIZE * (block_start_row + r) + block_start_col + c);
}
}
}
#[inline(always)]
fn block_ok(&self, nr: u8) -> bool {
let mut block = [0; SIZE];
self.get_block(&mut block);
!block.contains(&nr)
}
#[inline(always)]
fn row_ok(&self, nr: u8) -> bool {
let mut row = [0; SIZE];
self.get_row(&mut row);
!row.contains(&nr)
}
#[inline(always)]
fn col_ok(&self, nr: u8) -> bool {
let mut col = [0; SIZE];
self.get_col(&mut col);
!col.contains(&nr)
}
#[inline(always)]
fn next(&mut self) -> bool {
if self.pos == self.num_fields - 1 {
let new_pos = self.pos + 1 + unsafe { *self.skipf.get_unchecked(self.pos + 1) as usize };
if new_pos >= NUM_FIELDS {
return false;
}
self.pos += 1;
self.pos = new_pos;
true
}
#[inline(always)]
fn prev(&mut self) -> bool {
if self.pos == 0 {
let new_pos = self.pos - 1 - unsafe { *self.skipb.get_unchecked(self.pos - 1) as usize };
if new_pos >= NUM_FIELDS {
return false;
}
self.pos -= 1;
self.pos = new_pos;
true
}
#[inline(always)]
fn solve(&mut self) {
let now = Instant::now();
if !self.solve_backtracking() {