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🔥 Remove some duplicated code and add shuffled directions
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@bal7hazar
bal7hazar committed Oct 8, 2024
1 parent 5d29202 commit 062bb58
Showing 1 changed file with 42 additions and 107 deletions.
149 changes: 42 additions & 107 deletions crates/map/src/helpers/greedy.cairo
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Original file line number Diff line number Diff line change
@@ -1,13 +1,17 @@
//! Greedy algorithm implementation for pathfinding.

// Core imports

use core::dict::{Felt252Dict, Felt252DictTrait};

// Internal imports

use origami_map::helpers::heap::{Heap, HeapTrait};
use origami_map::helpers::astar::Astar;
use origami_map::helpers::bitmap::Bitmap;
use origami_map::helpers::seeder::Seeder;
use origami_map::types::node::{Node, NodeTrait};
use origami_map::types::direction::Direction;
use origami_map::types::direction::{Direction, DirectionTrait};

#[generate_trait]
pub impl Greedy of GreedyTrait {
Expand All @@ -34,72 +38,40 @@ pub impl Greedy of GreedyTrait {
let mut visited: Felt252Dict<bool> = Default::default();
heap.add(start);
// [Compute] Evaluate the path until the target is reached
while !heap.is_empty() {
// [Compute] Get the node with the smallest heuristic cost (to the target)
let current: Node = heap.pop_front().unwrap();
while let Option::Some(current) = heap.pop_front() {
// [Compute] Get the less expensive node
visited.insert(current.position.into(), true);
// [Check] Stop if we reached the target
if current.position == target.position {
break;
}
// [Compute] Evaluate the neighbors for all 4 directions
if Self::check(grid, width, height, current.position, Direction::North, ref visited) {
let neighbor_position = current.position + width;
let seed = Seeder::shuffle(grid, current.position.into());
let mut directions = DirectionTrait::compute_shuffled_directions(seed);
let direction: Direction = DirectionTrait::pop_front(ref directions);
if Astar::check(grid, width, height, current.position, direction, ref visited) {
let neighbor_position = direction.next(current.position, width);
Self::assess(width, neighbor_position, current, target, ref heap);
}
if Self::check(grid, width, height, current.position, Direction::East, ref visited) {
let neighbor_position = current.position + 1;
let direction: Direction = DirectionTrait::pop_front(ref directions);
if Astar::check(grid, width, height, current.position, direction, ref visited) {
let neighbor_position = direction.next(current.position, width);
Self::assess(width, neighbor_position, current, target, ref heap);
}
if Self::check(grid, width, height, current.position, Direction::South, ref visited) {
let neighbor_position = current.position - width;
let direction: Direction = DirectionTrait::pop_front(ref directions);
if Astar::check(grid, width, height, current.position, direction, ref visited) {
let neighbor_position = direction.next(current.position, width);
Self::assess(width, neighbor_position, current, target, ref heap);
}
if Self::check(grid, width, height, current.position, Direction::West, ref visited) {
let neighbor_position = current.position - 1;
let direction: Direction = DirectionTrait::pop_front(ref directions);
if Astar::check(grid, width, height, current.position, direction, ref visited) {
let neighbor_position = direction.next(current.position, width);
Self::assess(width, neighbor_position, current, target, ref heap);
}
};

// [Return] The path from the start to the target
Self::path(ref heap, start, target)
}

/// Check if the position can be visited in the specified direction.
/// # Arguments
/// * `grid` - The grid to search (1 is walkable and 0 is not)
/// * `width` - The width of the grid
/// * `height` - The height of the grid
/// * `position` - The current position
/// * `direction` - The direction to check
/// * `visited` - The visited nodes
/// # Returns
/// * Whether the position can be visited in the specified direction
#[inline]
fn check(
grid: felt252,
width: u8,
height: u8,
position: u8,
direction: Direction,
ref visited: Felt252Dict<bool>
) -> bool {
let (x, y) = (position % width, position / width);
match direction {
Direction::North => (y < height - 1)
&& (Bitmap::get(grid, position + width) == 1)
&& !visited.get((position + width).into()),
Direction::East => (x < width - 1)
&& (Bitmap::get(grid, position + 1) == 1)
&& !visited.get((position + 1).into()),
Direction::South => (y > 0)
&& (Bitmap::get(grid, position - width) == 1)
&& !visited.get((position - width).into()),
Direction::West => (x > 0)
&& (Bitmap::get(grid, position - 1) == 1)
&& !visited.get((position - 1).into()),
_ => false,
}
Astar::path(ref heap, start, target)
}

/// Assess the neighbor node and update the heap.
Expand All @@ -115,7 +87,7 @@ pub impl Greedy of GreedyTrait {
fn assess(
width: u8, neighbor_position: u8, current: Node, target: Node, ref heap: Heap<Node>,
) {
let neighbor_hcost = Self::heuristic(neighbor_position, target.position, width);
let neighbor_hcost = Astar::heuristic(neighbor_position, target.position, width);
let mut neighbor = match heap.get(neighbor_position.into()) {
Option::Some(node) => node,
Option::None => NodeTrait::new(neighbor_position, current.position, 0, neighbor_hcost),
Expand All @@ -126,49 +98,6 @@ pub impl Greedy of GreedyTrait {
}
return heap.update(neighbor);
}

/// Compute the heuristic cost between two positions.
/// # Arguments
/// * `position` - The current position
/// * `target` - The target position
/// * `width` - The width of the grid
/// # Returns
/// * The heuristic cost between the two positions
#[inline]
fn heuristic(position: u8, target: u8, width: u8) -> u16 {
let (x1, y1) = (position % width, position / width);
let (x2, y2) = (target % width, target / width);
let dx = if x1 > x2 {
x1 - x2
} else {
x2 - x1
};
let dy = if y1 > y2 {
y1 - y2
} else {
y2 - y1
};
(dx + dy).into()
}

/// Reconstruct the path from the target to the start.
#[inline]
fn path(ref heap: Heap<Node>, start: Node, target: Node) -> Span<u8> {
let mut path: Array<u8> = array![];
match heap.get(target.position) {
Option::None => { path.span() },
Option::Some(mut current) => {
loop {
if current.position == start.position {
break;
}
path.append(current.position);
current = heap.at(current.source);
};
path.span()
},
}
}
}

#[cfg(test)]
Expand All @@ -177,6 +106,9 @@ mod test {

#[test]
fn test_greedy_search_small() {
// x * *
// 1 0 *
// 0 1 s
let grid: felt252 = 0x1EB;
let width = 3;
let height = 3;
Expand All @@ -188,6 +120,9 @@ mod test {

#[test]
fn test_greedy_search_impossible() {
// x 1 0
// 1 0 1
// 0 1 s
let grid: felt252 = 0x1AB;
let width = 3;
let height = 3;
Expand All @@ -203,13 +138,13 @@ mod test {
// 0 0 0 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0
// 0 0 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0
// 0 0 1 1 1 1 1 0 1 1 0 0 0 0 0 0 0 0
// 0 0 0 1 1 1 1 ┌───x 0 0 0 0 0 0 0 0
// 0 0 0 0 1 1 1 │ 0 0 0 1 0 0 1 0 0 0
// 0 0 0 1 1 1 1 │ 0 0 0 ┌───────┐ 0 0
// 0 0 1 1 1 1 1 └───────┘ 1 1 1 └─┐ 0
// 0 0 0 1 1 1 1 0 1 1 1 0 1 1 1 1 │ 0
// 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 │ 0
// 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 s 0
// 0 0 0 1 1 1 1 * * x 0 0 0 0 0 0 0 0
// 0 0 0 0 1 1 1 * 0 0 0 1 0 0 1 0 0 0
// 0 0 0 1 1 1 1 * 0 0 0 * * * 1 1 0 0
// 0 0 1 1 1 1 1 * * * * * 1 * 1 1 1 0
// 0 0 0 1 1 1 1 0 1 1 1 0 1 * * 1 1 0
// 0 0 0 0 1 1 1 1 1 1 1 1 1 1 * * 1 0
// 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 * s 0
// 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 0
// 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 0
// 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Expand All @@ -236,12 +171,12 @@ mod test {
132,
131,
130,
129,
128,
110,
109,
91,
73
112,
94,
93,
75,
74,
56
]
.span()
);
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