diff --git a/torch_struct/semimarkov.py b/torch_struct/semimarkov.py
index 3f4a4942..eda04753 100644
--- a/torch_struct/semimarkov.py
+++ b/torch_struct/semimarkov.py
@@ -60,21 +60,15 @@ def _dp(self, log_potentials, lengths=None, force_grad=False):
                         chart[0][:, b, : end - (k - 1), k - 1, k].diagonal(0, 2, 3)
                     )
 
+        K_1 = K-1
         # Scan
         def merge(x, size):
-            return semiring.sum(
-                semiring.sum(
-                    semiring.times(
-                        x[:, :, 0 : size * 2 : 2]
-                        .transpose(-1, -2)
-                        .transpose(-3, -4)
-                        .view(ssize, batch, size, 1, K - 1, K - 1, 1, C, C),
-                        x[:, :, 1 : size * 2 : 2].view(
-                            ssize, batch, size, K - 1, 1, K - 1, C, 1, C
-                        ),
-                    )
-                ).transpose(-1, 5)
-            ).transpose(-1, -2)
+            left = x[:, :, 0 : size * 2 : 2].permute(0, 1, 2, 4, 6, 3, 5)
+            right = x[:, :, 1 : size * 2 : 2].permute(0, 1, 2, 3, 5, 4, 6)
+            return semiring.dot(
+                    left.view(ssize, batch, size, 1, K_1, 1, C, K_1* C),
+                    right.view(ssize, batch, size, K_1, 1, C, 1, K_1* C),
+                )
 
         size = bin_N
         for n in range(1, log_N + 1):