// 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 op_sp_stddev
//! @{

template <typename T1>
inline void op_sp_stddev::apply(
    Mat<typename T1::pod_type>& out,
    const mtSpReduceOp<typename T1::pod_type, T1, op_sp_stddev>& in) {
  arma_debug_sigprint();

  const uword norm_type = in.aux_uword_a;
  const uword dim = in.aux_uword_b;

  arma_conform_check((norm_type > 1), "stddev(): parameter 'norm_type' must be 0 or 1");
  arma_conform_check((dim > 1), "stddev(): parameter 'dim' must be 0 or 1");

  const SpProxy<T1> p(in.m);

  const uword p_n_rows = p.get_n_rows();
  const uword p_n_cols = p.get_n_cols();

  if ((p_n_rows == 0) || (p_n_cols == 0) || (p.get_n_nonzero() == 0)) {
    if (dim == 0) {
      out.zeros((p_n_rows > 0) ? 1 : 0, p_n_cols);
    }
    if (dim == 1) {
      out.zeros(p_n_rows, (p_n_cols > 0) ? 1 : 0);
    }

    return;
  }

  op_sp_stddev::apply_slow(out, p, norm_type, dim);
}

template <typename T1>
inline void op_sp_stddev::apply_slow(Mat<typename T1::pod_type>& out,
                                     const SpProxy<T1>& p, const uword norm_type,
                                     const uword dim) {
  arma_debug_sigprint();

  typedef typename T1::elem_type in_eT;
  // typedef typename T1::pod_type  out_eT;

  const uword p_n_rows = p.get_n_rows();
  const uword p_n_cols = p.get_n_cols();

  if (dim == 0)  // find variance in each column
  {
    arma_debug_print("op_sp_stddev::apply_slow(): dim = 0");

    out.zeros(1, p_n_cols);

    for (uword col = 0; col < p_n_cols; ++col) {
      if (SpProxy<T1>::use_iterator) {
        // We must use an iterator; we can't access memory directly.
        typename SpProxy<T1>::const_iterator_type it = p.begin_col(col);
        typename SpProxy<T1>::const_iterator_type end = p.begin_col(col + 1);

        const uword n_zero = p_n_rows - (end.pos() - it.pos());

        // in_eT is used just to get the specialization right (complex / noncomplex)
        out.at(0, col) =
            std::sqrt(op_sp_var::iterator_var(it, end, n_zero, norm_type, in_eT(0)));
      } else {
        // We can use direct memory access to calculate the variance.
        out.at(0, col) = std::sqrt(op_sp_var::direct_var(
            &p.get_values()[p.get_col_ptrs()[col]],
            p.get_col_ptrs()[col + 1] - p.get_col_ptrs()[col], p_n_rows, norm_type));
      }
    }
  } else if (dim == 1)  // find variance in each row
  {
    arma_debug_print("op_sp_stddev::apply_slow(): dim = 1");

    out.zeros(p_n_rows, 1);

    for (uword row = 0; row < p_n_rows; ++row) {
      // We have to use an iterator here regardless of whether or not we can
      // directly access memory.
      typename SpProxy<T1>::const_row_iterator_type it = p.begin_row(row);
      typename SpProxy<T1>::const_row_iterator_type end = p.end_row(row);

      const uword n_zero = p_n_cols - (end.pos() - it.pos());

      out.at(row, 0) =
          std::sqrt(op_sp_var::iterator_var(it, end, n_zero, norm_type, in_eT(0)));
    }
  }
}

template <typename T1>
inline typename T1::pod_type op_sp_stddev::stddev_vec(const T1& X,
                                                      const uword norm_type) {
  arma_debug_sigprint();

  typedef typename T1::pod_type T;

  arma_conform_check((norm_type > 1), "stddev(): parameter 'norm_type' must be 0 or 1");

  // conditionally unwrap it into a temporary and then directly operate.

  const unwrap_spmat<T1> tmp(X);

  if (tmp.M.n_elem == 0) {
    arma_conform_check(true, "stddev(): object has no elements");

    return Datum<T>::nan;
  }

  return std::sqrt(
      op_sp_var::direct_var(tmp.M.values, tmp.M.n_nonzero, tmp.M.n_elem, norm_type));
}

//! @}
