96 lines
2.6 KiB
C++
96 lines
2.6 KiB
C++
// 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 fn_inplace_strans
|
|
//! @{
|
|
|
|
|
|
|
|
template<typename eT>
|
|
inline
|
|
void
|
|
inplace_strans
|
|
(
|
|
Mat<eT>& X,
|
|
const char* method = "std"
|
|
)
|
|
{
|
|
arma_debug_sigprint();
|
|
|
|
const char sig = (method != nullptr) ? method[0] : char(0);
|
|
|
|
arma_conform_check( ((sig != 's') && (sig != 'l')), "inplace_strans(): unknown method specified" );
|
|
|
|
const bool low_memory = (sig == 'l');
|
|
|
|
if( (low_memory == false) || (X.n_rows == X.n_cols) )
|
|
{
|
|
op_strans::apply_mat_inplace(X);
|
|
}
|
|
else
|
|
{
|
|
// in-place algorithm inspired by:
|
|
// Fred G. Gustavson, Tadeusz Swirszcz.
|
|
// In-Place Transposition of Rectangular Matrices.
|
|
// Applied Parallel Computing. State of the Art in Scientific Computing.
|
|
// Lecture Notes in Computer Science. Volume 4699, pp. 560-569, 2007.
|
|
|
|
|
|
// X.set_size() will check whether we can change the dimensions of X;
|
|
// X.set_size() will also reuse existing memory, as the number of elements hasn't changed
|
|
|
|
X.set_size(X.n_cols, X.n_rows);
|
|
|
|
const uword m = X.n_cols;
|
|
const uword n = X.n_rows;
|
|
|
|
std::vector<bool> visited(X.n_elem); // TODO: replace std::vector<bool> with a better implementation
|
|
|
|
for(uword col = 0; col < m; ++col)
|
|
for(uword row = 0; row < n; ++row)
|
|
{
|
|
const uword pos = col*n + row;
|
|
|
|
if(visited[pos] == false)
|
|
{
|
|
uword curr_pos = pos;
|
|
|
|
eT val = X.at(row, col);
|
|
|
|
while(visited[curr_pos] == false)
|
|
{
|
|
visited[curr_pos] = true;
|
|
|
|
const uword j = curr_pos / m;
|
|
const uword i = curr_pos - m * j;
|
|
|
|
const eT tmp = X.at(j, i);
|
|
X.at(j, i) = val;
|
|
val = tmp;
|
|
|
|
curr_pos = i*n + j;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
//! @}
|