/*!
 *  Copyright (c) 2017 by Contributors
 * \brief Binary op constructions
 * \file nn/bnn.h
 */
#ifndef TOPI_NN_BNN_H_
#define TOPI_NN_BNN_H_

#include <string>

#include "tvm/tvm.h"
#include "tvm/ir_pass.h"
#include "topi/tags.h"
#include "topi/detail/constant_utils.h"

namespace topi {
namespace nn {
using namespace tvm;

/*!
* \brief Binarization and bit-packing along a certain axis.
*
* \param data N-D tensor, can be any layout
* \param axis The axis along which to do binarization and bit-packing. This axis
* must have a size equal to an integer multiple of 32.
* \param name The name of the operation
* \param tag The tag to mark the operation
*
* \return Output tensor with dtype uint32
*/
inline tvm::Tensor binarize_pack(const tvm::Tensor& data,
                                 int axis,
                                 std::string name = "PackedInput",
                                 std::string tag = "binarize_pack") {
  auto ishape = data->shape;
  CHECK_EQ(GetConstInt(ishape[axis]) % 32, 0)
    << "binarize_pack: axis size must be a multiple of 32";

  auto n = ishape.size();
  Array<Expr> oshape;
  for (size_t i = 0; i < n; ++i) {
    oshape.push_back(i == static_cast<size_t>(axis) ?
                     tvm::ir::Simplify(ishape[i] / 32) :
                     ishape[i]);
  }

  return tvm::compute(
    oshape,
    [&](const Array<Var>& indices) {
      Array<Expr> start_idx;
      for (size_t i = 0; i < n; ++i) {
        start_idx.push_back(i == static_cast<size_t>(axis) ?
                            indices[i] * 32 :
                            static_cast<Expr>(indices[i]));
      }
      auto packed = make_const(UInt(32), 0);
      for (size_t j = 0; j < 32; ++j) {
        Array<Expr> idx;
        for (size_t i = 0; i < n; ++i) {
          idx.push_back(i == static_cast<size_t>(axis) ?
                        start_idx[i] + static_cast<int>(j) :
                        start_idx[i]);
        }
        auto sign = tvm::cast(UInt(32), data(idx) >= 0);
        packed = (packed | sign);
        if (j == 31) {
          return packed;
        }
        packed = packed << 1;
      }
      return packed;  // never reached, but suppress compiler warning
    }, name, tag);
}

/*!
* \brief Binary matrix multiplication using xor and bit-count
*
* \param data Tensor with shape [batch, in_dim], dtype is uint32
* \param weight Tensor with shape [out_dim, in_dim], dtype is uint32
*
* \return Tensor with shape [batch, out_dim], dtype is float32
*/
inline tvm::Tensor binary_dense(const tvm::Tensor& data,
                                const tvm::Tensor& weight) {
  CHECK_EQ(data->shape.size(), 2) << "binary_dense requires 2-D data";
  CHECK_EQ(weight->shape.size(), 2) << "binary_dense requires 2-D weight";
  CHECK_EQ(data->dtype, UInt(32)) << "binary_dense requires uint32 data";
  CHECK_EQ(weight->dtype, UInt(32)) << "binary_dense requires uint32 weight";

  auto batch = data->shape[0];
  auto in_dim = data->shape[1];
  auto out_dim = weight->shape[0];

  auto k = tvm::reduce_axis(Range(0, in_dim), "k");
  auto matmul = tvm::compute(
    { batch, out_dim },
    [&](Var i, Var j) {
      return tvm::sum(popcount(data(i, k) ^ weight(j, k)), { k });
    }, "tensor", "binary_dense");

  return tvm::compute(
    { batch, out_dim },
    [&](Var i, Var j) {
      return 32 * in_dim - 2.0f * matmul(i, j);
    }, "tensor", kElementWise);
}

}  // namespace nn
}  // namespace topi
#endif  // TOPI_NN_BNN_H_
