MPS support workaround for complex tensors

Avoid repeat() on complex tensors in MPS by using cat fallback using torch.cat on MPS.

Resolves the runtime error 'repeat(): Not supported for complex yet!'

sam2/modeling/position_encoding.py

@@ -211,6 +211,10 @@ def apply_rotary_enc(
     # repeat freqs along seq_len dim to match k seq_len
     if repeat_freqs_k:
         r = xk_.shape[-2] // xq_.shape[-2]
-        freqs_cis = freqs_cis.repeat(*([1] * (freqs_cis.ndim - 2)), r, 1)
+        if freqs_cis.is_complex() and freqs_cis.device.type == "mps":
+            # MPS doesn't support repeat on complex; cat works fine.
+            freqs_cis = torch.cat([freqs_cis] * r, dim=-2)
+        else:
+            freqs_cis = freqs_cis.repeat(*([1] * (freqs_cis.ndim - 2)), r, 1)
     xk_out = torch.view_as_real(xk_ * freqs_cis).flatten(3)
     return xq_out.type_as(xq).to(xq.device), xk_out.type_as(xk).to(xk.device)