// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2008-2016 Conrad Sanderson (http://conradsanderson.id.au)
// Copyright 2008-2016 National ICT Australia (NICTA)
//
// 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.
// ------------------------------------------------------------------------

//! \addtogroup mtSpReduceOp
//! @{

// NOTE: mtSpReduceOp is dedicated for reduction operations on sparse matrices,
// NOTE: including sum(), min(), max(), mean(), var(), stddev(),
// NOTE  where the entire sparse matrix is reduced to a vector.
// NOTE:
// NOTE: Even though it would make more sense for mtSpReduceOp to be derived from Base
// NOTE: (as it's more efficient to store the resulting vectors in dense format),
// NOTE: mtSpReduceOp is derived from SpBase so the default user-accessible output is in
// sparse storage format. NOTE. This is to mimic the behaviour of Octave and to keep
// compatibility with existing user code. NOTE: NOTE: However, for simplicity and
// efficiency, each mtSpReduceOp op_type::apply() function NOTE: must output to a dense
// matrix, ie. apply(Mat, ...). NOTE: The SpMat class handles mtSpReduceOp by converting
// the dense output to a sparse representation. NOTE: The Mat class has an explicit
// constructor to efficiently handle mtSpReduceOp.

template <typename out_eT, typename T1, typename op_type>
class mtSpReduceOp : public SpBase<out_eT, mtSpReduceOp<out_eT, T1, op_type> > {
 public:
  typedef out_eT elem_type;
  typedef typename get_pod_type<out_eT>::result pod_type;

  typedef typename T1::elem_type in_eT;

  static constexpr bool is_row = op_type::template traits<T1>::is_row;
  static constexpr bool is_col = op_type::template traits<T1>::is_col;
  static constexpr bool is_xvec = op_type::template traits<T1>::is_xvec;

  inline explicit mtSpReduceOp(const T1& in_m);
  inline mtSpReduceOp(const T1& in_m, const uword in_aux_uword_a,
                      const uword in_aux_uword_b);
  inline ~mtSpReduceOp();

  arma_aligned const T1& m;        //!< the operand; must be derived from SpBase
  arma_aligned uword aux_uword_a;  //!< auxiliary data, uword format
  arma_aligned uword aux_uword_b;  //!< auxiliary data, uword format
};

//! @}
