No atan

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## [0.2.2] - 2025-11-09
+- performance atan2 
+- parformance unstable sort (total 64%)
+
 ## [0.2.0] - 2025-11-09
 - Error enum for returning the exact cause.
 - Added test/benchmark data generators.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "nfp"
-version = "0.2.1"
+version = "0.2.2"
 edition = "2024"
 description = "No Fit Polygon"
 categories = ["science::geo", "data-structures", "game-development", "graphics"]

benches/nfp_bench100.rs

@@ -33,7 +33,7 @@ fn main() {
     println!("\nResults:");
     println!("--------");
     println!("Total time:     {:?}", elapsed);
-    println!("Time per run:   {:.3} ms", elapsed.as_secs_f64() * 1000.0 / ITERATIONS as f64);
+    println!("Time per run:   {:.3} μs", elapsed.as_secs_f64() * 1_000_000.0 / ITERATIONS as f64);
     println!("Runs per sec:   {:.0}", ITERATIONS as f64 / elapsed.as_secs_f64());
 }
 
@@ -82,8 +82,7 @@ fn compute_centroid(points: &[Point]) -> Point {
 }
 
 /*
-cargo bench --bench nfp_benchmark
-samply record cargo run --release --example perf_build
+cargo bench --bench nfp_bench100
 
 Iterations: 1000
 
@@ -99,5 +98,16 @@ Total time:     4.152361987s
 Time per run:   4.152 ms
 Runs per sec:   241
 _______________________________________________
+Opt 1 ditch atan2
 
+Total time:     1.725334029s
+Time per run:   1725.334 μs
+Runs per sec:   580
+_______________________________________________
+Opt2 unstable sorting
+
+Total time:     1.44724319s
+Time per run:   1447.243 μs
+Runs per sec:   691
+_______________________________________________
 */

benches/nfp_bench200.rs

@@ -33,7 +33,7 @@ fn main() {
     println!("\nResults:");
     println!("--------");
     println!("Total time:     {:?}", elapsed);
-    println!("Time per run:   {:.3} ms", elapsed.as_secs_f64() * 1000.0 / ITERATIONS as f64);
+    println!("Time per run:   {:.3} μs", elapsed.as_secs_f64() * 1_000_000.0 / ITERATIONS as f64);
     println!("Runs per sec:   {:.0}", ITERATIONS as f64 / elapsed.as_secs_f64());
 }
 
@@ -82,8 +82,7 @@ fn compute_centroid(points: &[Point]) -> Point {
 }
 
 /*
-cargo bench --bench nfp_benchmark
-
+cargo bench --bench nfp_bench200
 
 Iterations: 300
 
@@ -99,5 +98,16 @@ Total time:     5.604518697s
 Time per run:   18.682 ms
 Runs per sec:   54
 _______________________________________________
+Opt 1 ditch atan2
+
+Total time:     2.456991368s
+Time per run:   8189.971 μs
+Runs per sec:   122
+_______________________________________________
+Opt2 unstable sorting
 
+Total time:     2.027956028s
+Time per run:   6759.853 μs
+Runs per sec:   148
+_______________________________________________
 */

benches/nfp_bench500.rs

@@ -33,7 +33,7 @@ fn main() {
     println!("\nResults:");
     println!("--------");
     println!("Total time:     {:?}", elapsed);
-    println!("Time per run:   {:.3} ms", elapsed.as_secs_f64() * 1000.0 / ITERATIONS as f64);
+    println!("Time per run:   {:.3} μs", elapsed.as_secs_f64() * 1_000_000.0 / ITERATIONS as f64);
     println!("Runs per sec:   {:.0}", ITERATIONS as f64 / elapsed.as_secs_f64());
 }
 
@@ -82,8 +82,7 @@ fn compute_centroid(points: &[Point]) -> Point {
 }
 
 /*
-cargo bench --bench nfp_benchmark
-
+cargo bench --bench nfp_bench500
 
 Iterations: 100
 
@@ -99,5 +98,16 @@ Total time:     13.578851406s
 Time per run:   135.789 ms
 Runs per sec:   7
 _______________________________________________
+Opt 1 ditch atan2
+
+Total time:     6.140549308s
+Time per run:   61405.493 μs
+Runs per sec:   16
+_______________________________________________
+Opt2 unstable sorting
 
+Total time:     4.848619896s
+Time per run:   48486.199 μs
+Runs per sec:   21
+_______________________________________________
 */

src/nfp_points.rs

@@ -157,7 +157,7 @@ impl NFP {
 
         // Remove near-duplicate points (within tolerance)
         let tolerance = 1e-10;
-        nfp_vertices.sort_by(|a, b| {
+        nfp_vertices.sort_unstable_by(|a, b| {
             a.x.partial_cmp(&b.x)
                 .unwrap_or(std::cmp::Ordering::Equal)
                 .then_with(|| a.y.partial_cmp(&b.y).unwrap_or(std::cmp::Ordering::Equal))
@@ -166,13 +166,9 @@ impl NFP {
             (a.x - b.x).abs() < tolerance && (a.y - b.y).abs() < tolerance
         });
 
-        // Sort vertices in CCW order by angle from centroid
+        // Sort vertices in CCW order by angle from centroid (avoid atan2)
         let centroid = compute_centroid(&nfp_vertices);
-        nfp_vertices.sort_by(|a, b| {
-            let angle_a = (a.y - centroid.y).atan2(a.x - centroid.x);
-            let angle_b = (b.y - centroid.y).atan2(b.x - centroid.x);
-            angle_a.partial_cmp(&angle_b).unwrap_or(std::cmp::Ordering::Equal)
-        });
+        nfp_vertices.sort_unstable_by(|a, b| angle_cmp(a, b, &centroid));
 
         Ok(nfp_vertices)
     }
@@ -190,6 +186,39 @@ fn compute_centroid(points: &[Point]) -> Point {
     Point::new(sum_x / len, sum_y / len)
 }
 
+/// Tolerance for comparing collinear points in angle sorting
+const ANGLE_CMP_EPSILON: f64 = 1e-10;
+
+// Compare points by angle around a given `centroid` without using `atan2`.
+// Uses half-plane test and perp (2D cross product) to determine CCW ordering.
+fn angle_cmp(a: &Point, b: &Point, centroid: &Point) -> std::cmp::Ordering {
+    use std::cmp::Ordering;
+
+    let ax = a.x - centroid.x;
+    let ay = a.y - centroid.y;
+    let bx = b.x - centroid.x;
+    let by = b.y - centroid.y;
+
+    // Place points into two half-planes: upper (y>0 or y==0 && x>=0) and lower.
+    let a_up = (ay > 0.0) || (ay == 0.0 && ax >= 0.0);
+    let b_up = (by > 0.0) || (by == 0.0 && bx >= 0.0);
+    if a_up != b_up {
+        // a_up true should come before b_up false
+        return a_up.cmp(&b_up).reverse();
+    }
+
+    // Same half-plane: use perp (2D cross product) to determine order
+    let perp = ax * by - ay * bx;
+    if perp.abs() > ANGLE_CMP_EPSILON {
+        return if perp > 0.0 { Ordering::Less } else { Ordering::Greater };
+    }
+
+    // Collinear: sort by distance from centroid (closer first)
+    let da = ax * ax + ay * ay;
+    let db = bx * bx + by * by;
+    da.partial_cmp(&db).unwrap_or(Ordering::Equal)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;