Temporarily disables Split-KV feature

Author: LoserCheems

csrc/flash_api.cpp

@@ -255,6 +255,14 @@ std::tuple<at::Tensor, at::Tensor> set_params_splitkv(
         TORCH_CHECK(params.num_splits <= 128, "num_splits > 128 not supported");
     }
 
+    // Temporarily disable Split-KV, because some bugs are still being fixed.
+    // See: https://github.com/SmallDoges/flash-dmattn/issues/47
+    // Regardless of how it is set externally, always set num_splits back to 1.
+    // This is to avoid the extra memory overhead of Split-KV.
+    params.num_splits = 1;
+    softmax_lse_accum.reset();
+    out_accum.reset();
+
     return std::make_tuple(softmax_lse_accum, out_accum);
 }