// Copyright (c) 2024 PaddlePaddle Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <algorithm>
#include <utility>
#include <vector>

#include "paddle/phi/core/dense_tensor.h"
#include "paddle/phi/core/kernel_registry.h"

#if defined(PADDLE_WITH_GLOO)
#include "paddle/phi/core/distributed/gloo_comm_context.h"
#endif

namespace phi {

template <typename T, typename Context>
void CScatterOpCPUKernel(const Context &dev_ctx,
                         const DenseTensor &x,
                         int ring_id,
                         int root,
                         int nranks,
                         bool use_calc_stream,
                         DenseTensor *out) {
#if defined(PADDLE_WITH_GLOO)
  auto in = &x;
  auto root_id = root;

  auto comm_ctx =
      static_cast<distributed::GlooCommContext *>(dev_ctx.GetCommContext());
  PADDLE_ENFORCE_NE(comm_ctx,
                    nullptr,
                    ::common::errors::Unavailable(
                        "NCCLCommContext is nullptr, collective op should "
                        "has ring_id attr."));
  comm_ctx->Scatter(out, *in, root_id);
#else
  PADDLE_THROW(common::errors::Unavailable(
      "PaddlePaddle should compile with GLOO by setting WITH_GLOO=ON"));
#endif
}
}  // namespace phi

PD_REGISTER_KERNEL(c_scatter,
                   CPU,
                   ALL_LAYOUT,
                   phi::CScatterOpCPUKernel,
                   float,
                   double,
                   int,
                   int64_t,
                   phi::float16) {}