// 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 spop_strans
//! @{

template <typename eT>
inline void spop_strans::apply_noalias(SpMat<eT>& B, const SpMat<eT>& A) {
  arma_debug_sigprint();

  B.reserve(A.n_cols, A.n_rows, A.n_nonzero);  // deliberately swapped

  if (A.n_nonzero == 0) {
    return;
  }

  // This follows the TRANSP algorithm described in
  // 'Sparse Matrix Multiplication Package (SMMP)'
  // (R.E. Bank and C.C. Douglas, 2001)

  const uword m = A.n_rows;
  const uword n = A.n_cols;

  const eT* a = A.values;
  eT* b = access::rwp(B.values);

  const uword* ia = A.col_ptrs;
  const uword* ja = A.row_indices;

  uword* ib = access::rwp(B.col_ptrs);
  uword* jb = access::rwp(B.row_indices);

  // // ib is already zeroed, as B is freshly constructed
  //
  // for(uword i=0; i < (m+1); ++i)
  //   {
  //   ib[i] = 0;
  //   }

  for (uword i = 0; i < n; ++i) {
    for (uword j = ia[i]; j < ia[i + 1]; ++j) {
      ib[ja[j] + 1]++;
    }
  }

  for (uword i = 0; i < m; ++i) {
    ib[i + 1] += ib[i];
  }

  for (uword i = 0; i < n; ++i) {
    for (uword j = ia[i]; j < ia[i + 1]; ++j) {
      const uword jj = ja[j];

      const uword ib_jj = ib[jj];

      jb[ib_jj] = i;

      b[ib_jj] = a[j];

      ib[jj]++;
    }
  }

  for (uword i = m - 1; i >= 1; --i) {
    ib[i] = ib[i - 1];
  }

  ib[0] = 0;
}

template <typename T1>
inline void spop_strans::apply(SpMat<typename T1::elem_type>& out,
                               const SpOp<T1, spop_strans>& in) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  const unwrap_spmat<T1> U(in.m);

  if (U.is_alias(out)) {
    SpMat<eT> tmp;

    spop_strans::apply_noalias(tmp, U.M);

    out.steal_mem(tmp);
  } else {
    spop_strans::apply_noalias(out, U.M);
  }
}

//! for transpose of non-complex matrices, redirected from spop_htrans::apply()
template <typename T1>
inline void spop_strans::apply(SpMat<typename T1::elem_type>& out,
                               const SpOp<T1, spop_htrans>& in) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  const unwrap_spmat<T1> U(in.m);

  if (U.is_alias(out)) {
    SpMat<eT> tmp;

    spop_strans::apply_noalias(tmp, U.M);

    out.steal_mem(tmp);
  } else {
    spop_strans::apply_noalias(out, U.M);
  }
}

//! @}
