Fix inverse RoPE formula: swap signs on cross terms

2026-05-19 03:22:10 +00:00
parent fece06f746
commit 4ed91b81d0
1 changed files with 2 additions and 2 deletions
--- a/vllm/patches/deepseek_v4_attention.py
+++ b/vllm/patches/deepseek_v4_attention.py
@@ -583,9 +583,9 @@ def _apply_inv_rope_bf16(
    rope = o_f32[..., nope_dim:]
    y_even = rope[..., 0::2]
    y_odd = rope[..., 1::2]
-    # Inverse: sin → -sin
+    # Inverse: sin → -sin (swap signs on the cross terms)
    rope_out = torch.stack(
-        (y_even * cos - y_odd * sin, y_odd * cos + y_even * sin),
+        (y_even * cos + y_odd * sin, y_odd * cos - y_even * sin),
        dim=-1,
    ).flatten(-2)
    o_f32 = o_f32.clone()