Optimization: early exit get_aggressive_path -93%

Added a benchmark task where the player is near.
On the task where the player is near, big speedup. No change for task
where player is far (previous benchmark).
This should make a good difference in real play, since the bot is
chasing us it shouldn't always on the other side of the map.

bot/benches/benchmarks.rs

@@ -4,26 +4,32 @@ use pprof::criterion::{Output, PProfProfiler};
 use devnull_bot::simulation::{get_aggressive_path, make_grid, Pos};
 
 pub fn criterion_benchmark(c: &mut Criterion) {
-    c.bench_function("get_aggressive_path 22x15", |b| {
-        let grid = make_grid(vec![
-            "######################",
-            "#                    #",
-            "# ########  ######## #",
-            "# #                # #",
-            "# #### ###  # #### # #",
-            "# ####      # #### # #",
-            "# #### ###  # #### # #",
-            "#           # #      #",
-            "# #### ###  # # #### #",
-            "# #  #      # # #  # #",
-            "# #    ###  # #    # #",
-            "# #                # #",
-            "# ########  ######## #",
-            "#                    #",
-            "######################",
-        ]);
+    let grid = make_grid(vec![
+        "######################",
+        "#                    #",
+        "# ########  ######## #",
+        "# #                # #",
+        "# #### ###  # #### # #",
+        "# ####      # #### # #",
+        "# #### ###  # #### # #",
+        "#           # #      #",
+        "# #### ###  # # #### #",
+        "# #  #      # # #  # #",
+        "# #    ###  # #    # #",
+        "# #                # #",
+        "# ########  ######## #",
+        "#                    #",
+        "######################",
+    ]);
+    c.bench_function("get_aggressive_path 22x15 far", |b| {
         b.iter(|| get_aggressive_path(
-                black_box(&grid), &Pos { x: 5, y: 1 }, &Pos { x: 18, y: 13 }));
+                black_box(&grid), black_box(&Pos { x: 5, y: 1 }),
+                black_box(&Pos { x: 18, y: 13 })));
+    });
+    c.bench_function("get_aggressive_path 22x15 close", |b| {
+        b.iter(|| get_aggressive_path(
+                black_box(&grid), black_box(&Pos { x: 5, y: 1 }),
+                black_box(&Pos { x: 9, y: 1 })));
     });
 }
 

bot/src/simulation.rs

@@ -184,7 +184,6 @@ pub fn get_aggressive_path(grid: &Grid, from: &Pos, to: &Pos) -> Vec<Pos> {
     // - sort is called at the start of the loop, so any newly added nodes in
     //   the same loop will keep their initial relative order from 'empty_tiles'
     //   instead of being in the order seen
-    // TODO: can early exit if found target
     // TODO: Refactor to a struct, impl old slower method, unit test verifying
     //       that the behavior is the same.
     const HIGH_COST: usize = 9999999;
@@ -202,6 +201,10 @@ pub fn get_aggressive_path(grid: &Grid, from: &Pos, to: &Pos) -> Vec<Pos> {
             frontier_cost += 1;
         }
         let pos = frontier.pop_back().unwrap();
+        if pos == *to {
+            // Early exit if we found the target
+            break;
+        }
         let mut frontier_adds = Vec::new();
         let mut next_frontier_adds = Vec::new();
         // Note: order is irrelevant, since we enforce order to match the JS