From e1770a3061df8064b95422febb8deff2b75c419a Mon Sep 17 00:00:00 2001
From: Andrej Karpathy <andrej.karpathy@gmail.com>
Date: Sat, 27 Dec 2025 23:07:48 +0000
Subject: [PATCH] remove spurious cast, gets compiled away anyway but it's
 confusing people

---
 nanochat/gpt.py | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/nanochat/gpt.py b/nanochat/gpt.py
index 9a80c7c..69899ee 100644
--- a/nanochat/gpt.py
+++ b/nanochat/gpt.py
@@ -41,12 +41,10 @@ def norm(x):
 def apply_rotary_emb(x, cos, sin):
     assert x.ndim == 4  # multihead attention
     d = x.shape[3] // 2
-    x1, x2 = x[..., :d], x[..., d:] # split up last time into two halves
+    x1, x2 = x[..., :d], x[..., d:] # split up last dim into two halves
     y1 = x1 * cos + x2 * sin # rotate pairs of dims
     y2 = x1 * (-sin) + x2 * cos
-    out = torch.cat([y1, y2], 3) # re-assemble
-    out = out.to(x.dtype) # ensure input/output dtypes match
-    return out
+    return torch.cat([y1, y2], 3)
 
 class CausalSelfAttention(nn.Module):
     def __init__(self, config, layer_idx):