diff -r aec67cdd6b14 -r efa60bc4f743 src/kernels/hat_convolution.rs
--- a/src/kernels/hat_convolution.rs	Tue Aug 01 10:32:12 2023 +0300
+++ b/src/kernels/hat_convolution.rs	Thu Aug 29 00:00:00 2024 -0500
@@ -97,7 +97,9 @@
         // |∏_{i=1}^N ψ_i(x_i) - ∏_{i=1}^N ψ_i(y_i)|
         // ≤ ∑_{j=1}^N |ψ_j(x_j)-ψ_j(y_j)| ∏_{j ≠ i} \max_i |ψ_i|
         let σ = self.radius();
-        Some((self.lipschitz_1d_σ1() / (σ*σ)) * (self.value_1d_σ1(0.0) / σ))
+        let l1d = self.lipschitz_1d_σ1() / (σ*σ);
+        let m1d = self.value_1d_σ1(0.0) / σ;
+        Some(l1d * m1d.powi(N as i32 - 1))
     }
 }
 
@@ -398,7 +400,7 @@
                 |y| (2.0/3.0) * (y + 1.0).powi(3),
                 || i(a, b, -0.5, 0.0,
                     // -2 y^3 - 2 y^2 + 1/3  on  -1/2 < y ≤ 0
-                    |y| -2.0*(y - 1.0) * y * y + (1.0/3.0),
+                    |y| -2.0*(y + 1.0) * y * y + (1.0/3.0),
                     || i(a, b, 0.0, 0.5,
                             // 2 y^3 - 2 y^2 + 1/3 on 0 < y < 1/2
                             |y| 2.0*(y - 1.0) * y * y + (1.0/3.0),