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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 fn_randperm
//! @{
template<typename obj_type>
inline
void
internal_randperm_helper(obj_type& x, const uword N, const uword N_keep)
{
arma_extra_debug_sigprint();
typedef typename obj_type::elem_type eT;
// see op_sort_index_bones.hpp for the definition of arma_sort_index_packet
// and the associated comparison functor
typedef arma_sort_index_packet<int> packet;
std::vector<packet> packet_vec(N);
for(uword i=0; i < N; ++i)
{
packet_vec[i].val = int(arma_rng::randi<int>());
packet_vec[i].index = i;
}
arma_sort_index_helper_ascend<int> comparator;
if(N >= 2)
{
if(N_keep < N)
{
typename std::vector<packet>::iterator first = packet_vec.begin();
typename std::vector<packet>::iterator nth = first + N_keep;
typename std::vector<packet>::iterator pastlast = packet_vec.end();
std::partial_sort(first, nth, pastlast, comparator);
}
else
{
std::sort( packet_vec.begin(), packet_vec.end(), comparator );
}
}
if(is_Row<obj_type>::value)
{
x.set_size(1,N_keep);
}
else
{
x.set_size(N_keep,1);
}
eT* x_mem = x.memptr();
for(uword i=0; i < N_keep; ++i)
{
x_mem[i] = eT( packet_vec[i].index );
}
}
template<typename obj_type>
arma_warn_unused
inline
typename enable_if2< is_Mat<obj_type>::value, obj_type >::result
randperm(const uword N)
{
arma_extra_debug_sigprint();
obj_type x;
if(N > 0) { internal_randperm_helper(x, N, N); }
return x;
}
arma_warn_unused
inline
uvec
randperm(const uword N)
{
arma_extra_debug_sigprint();
uvec x;
if(N > 0) { internal_randperm_helper(x, N, N); }
return x;
}
template<typename obj_type>
arma_warn_unused
inline
typename enable_if2< is_Mat<obj_type>::value, obj_type >::result
randperm(const uword N, const uword M)
{
arma_extra_debug_sigprint();
arma_debug_check( (M > N), "randperm(): 'M' must be less than or equal to 'N'" );
obj_type x;
if( (N > 0) && (M > 0) ) { internal_randperm_helper(x, N, M); }
return x;
}
arma_warn_unused
inline
uvec
randperm(const uword N, const uword M)
{
arma_extra_debug_sigprint();
arma_debug_check( (M > N), "randperm(): 'M' must be less than or equal to 'N'" );
uvec x;
if( (N > 0) && (M > 0) ) { internal_randperm_helper(x, N, M); }
return x;
}
//! @}
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