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armadillo-code/include/armadillo_bits/op_sp_mean_meat.hpp
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// 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_mean
//! @{
template<typename T1>
inline
void
op_sp_mean::apply(Mat<typename T1::elem_type>& out, const mtSpReduceOp<typename T1::elem_type, T1, op_sp_mean>& in)
{
arma_debug_sigprint();
const uword dim = in.aux_uword_a;
arma_conform_check( (dim > 1), "mean(): 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_mean::apply_fast(out, p, dim);
}
template<typename T1>
inline
void
op_sp_mean::apply_fast
(
Mat<typename T1::elem_type>& out,
const SpProxy<T1>& p,
const uword dim
)
{
arma_debug_sigprint();
typedef typename T1::elem_type eT;
typedef typename T1::pod_type T;
const uword p_n_rows = p.get_n_rows();
const uword p_n_cols = p.get_n_cols();
if(dim == 0) // find the mean in each column
{
arma_debug_print("op_sp_mean::apply_fast(): dim = 0");
out.zeros(1, p_n_cols);
eT* out_mem = out.memptr();
if(SpProxy<T1>::use_iterator)
{
typename SpProxy<T1>::const_iterator_type it = p.begin();
const uword N = p.get_n_nonzero();
for(uword i=0; i < N; ++i) { out_mem[it.col()] += (*it); ++it; }
out /= T(p_n_rows);
}
else
{
for(uword col = 0; col < p_n_cols; ++col)
{
out_mem[col] = arrayops::accumulate
(
&p.get_values()[p.get_col_ptrs()[col]],
p.get_col_ptrs()[col + 1] - p.get_col_ptrs()[col]
) / T(p_n_rows);
}
}
}
else
if(dim == 1) // find the mean in each row
{
arma_debug_print("op_sp_mean::apply_fast(): dim = 1");
out.zeros(p_n_rows, 1);
eT* out_mem = out.memptr();
typename SpProxy<T1>::const_iterator_type it = p.begin();
const uword N = p.get_n_nonzero();
for(uword i=0; i < N; ++i) { out_mem[it.row()] += (*it); ++it; }
out /= T(p_n_cols);
}
if(out.internal_has_nonfinite())
{
op_sp_mean::apply_slow(out, p, dim);
}
}
template<typename T1>
inline
void
op_sp_mean::apply_slow
(
Mat<typename T1::elem_type>& out,
const SpProxy<T1>& p,
const uword dim
)
{
arma_debug_sigprint();
typedef typename T1::elem_type eT;
const uword p_n_rows = p.get_n_rows();
const uword p_n_cols = p.get_n_cols();
if(dim == 0) // find the mean in each column
{
arma_debug_print("op_sp_mean::apply_slow(): dim = 0");
out.zeros(1, p_n_cols);
for(uword col = 0; col < p_n_cols; ++col)
{
// Do we have to use an iterator or can we use memory directly?
if(SpProxy<T1>::use_iterator)
{
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());
out.at(0,col) = op_sp_mean::iterator_mean(it, end, n_zero, eT(0));
}
else
{
out.at(0,col) = op_sp_mean::direct_mean
(
&p.get_values()[p.get_col_ptrs()[col]],
p.get_col_ptrs()[col + 1] - p.get_col_ptrs()[col],
p_n_rows
);
}
}
}
else
if(dim == 1) // find the mean in each row
{
arma_debug_print("op_sp_mean::apply_slow(): dim = 1");
out.zeros(p_n_rows, 1);
for(uword row = 0; row < p_n_rows; ++row)
{
// We must use an iterator regardless of how it is stored.
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) = op_sp_mean::iterator_mean(it, end, n_zero, eT(0));
}
}
}
template<typename eT>
inline
eT
op_sp_mean::direct_mean
(
const eT* const X,
const uword length,
const uword N
)
{
arma_debug_sigprint();
typedef typename get_pod_type<eT>::result T;
const eT result = ((length > 0) && (N > 0)) ? eT(arrayops::accumulate(X, length) / T(N)) : eT(0);
return arma_isfinite(result) ? result : op_sp_mean::direct_mean_robust(X, length, N);
}
template<typename eT>
inline
eT
op_sp_mean::direct_mean_robust
(
const eT* const X,
const uword length,
const uword N
)
{
arma_debug_sigprint();
typedef typename get_pod_type<eT>::result T;
uword i, j;
eT r_mean = eT(0);
const uword diff = (N - length); // number of zeros
for(i = 0, j = 1; j < length; i += 2, j += 2)
{
const eT Xi = X[i];
const eT Xj = X[j];
r_mean += (Xi - r_mean) / T(diff + j);
r_mean += (Xj - r_mean) / T(diff + j + 1);
}
if(i < length)
{
const eT Xi = X[i];
r_mean += (Xi - r_mean) / T(diff + i + 1);
}
return r_mean;
}
template<typename T1>
inline
typename T1::elem_type
op_sp_mean::mean_all(const SpBase<typename T1::elem_type, T1>& X)
{
arma_debug_sigprint();
typedef typename T1::elem_type eT;
SpProxy<T1> p(X.get_ref());
if(p.get_n_elem() == 0)
{
arma_conform_check(true, "mean(): object has no elements");
return Datum<eT>::nan;
}
if(SpProxy<T1>::use_iterator)
{
typename SpProxy<T1>::const_iterator_type it = p.begin();
typename SpProxy<T1>::const_iterator_type end = p.end();
return op_sp_mean::iterator_mean(it, end, p.get_n_elem() - p.get_n_nonzero(), typename T1::elem_type(0));
}
else // use_iterator == false; that is, we can directly access the values array
{
return op_sp_mean::direct_mean(p.get_values(), p.get_n_nonzero(), p.get_n_elem());
}
}
template<typename T1, typename spop_type>
inline
typename T1::elem_type
op_sp_mean::mean_all(const SpOp<T1, spop_type>& expr)
{
arma_debug_sigprint();
typedef typename T1::elem_type eT;
constexpr bool is_vectorise = \
(is_same_type<spop_type, spop_vectorise_row>::yes)
|| (is_same_type<spop_type, spop_vectorise_col>::yes)
|| (is_same_type<spop_type, spop_vectorise_all>::yes);
if(is_vectorise)
{
return op_sp_mean::mean_all(expr.m);
}
const SpMat<eT> tmp = expr;
return op_sp_mean::mean_all(tmp);
}
template<typename T1, typename eT>
inline
eT
op_sp_mean::iterator_mean(T1& it, const T1& end, const uword n_zero, const eT junk)
{
arma_debug_sigprint();
arma_ignore(junk);
typedef typename get_pod_type<eT>::result T;
eT acc = eT(0);
T1 backup_it(it); // in case we have to use robust iterator_mean
const uword it_begin_pos = it.pos();
while(it != end)
{
acc += (*it);
++it;
}
const uword count = n_zero + (it.pos() - it_begin_pos);
const eT result = (count > 0) ? eT(acc / T(count)) : eT(0);
return arma_isfinite(result) ? result : op_sp_mean::iterator_mean_robust(backup_it, end, n_zero, eT(0));
}
template<typename T1, typename eT>
inline
eT
op_sp_mean::iterator_mean_robust(T1& it, const T1& end, const uword n_zero, const eT junk)
{
arma_debug_sigprint();
arma_ignore(junk);
typedef typename get_pod_type<eT>::result T;
eT r_mean = eT(0);
const uword it_begin_pos = it.pos();
while(it != end)
{
r_mean += ((*it - r_mean) / T(n_zero + (it.pos() - it_begin_pos) + 1));
++it;
}
return r_mean;
}
//! @}