random_permutation.hh

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/// @file   numeric/random/random_permutation.hh
/// @brief  Reorder the elements in a vector using a RNG object
/// @author Andrew Leaver-Fay
///
/// @remarks
///  @li -


#ifndef INCLUDED_numeric_random_random_permutation_hh
#define INCLUDED_numeric_random_random_permutation_hh


// Unit headers
#include <numeric/random/random.hh>

// Utility headers
#include <utility/vector0.hh>
#include <utility/vector1.hh>

// C++ Headers
#include <algorithm>
#include <cmath>
#include <iostream>

namespace numeric {
namespace random {

template< class T >
void
random_permutation(
  utility::vector1< T > & vect,
  RandomGenerator & rg
)
{
  Size const vsize = vect.size();
  for ( Size ii = vsize; ii >= 2; --ii ) {
    Size swap_partner = static_cast< Size > (std::floor( ii*rg.uniform() + 1 ));

    T temp = vect[ swap_partner ];
    vect[ swap_partner ] = vect[ ii ];
    vect[ ii ] = temp;
  }
}

template< class T >
void
random_permutation(
  utility::vector0< T > & vect,
  RandomGenerator & rg
)
{
  Size const vsize = vect.size();
  for ( Size ii = vsize - 1; ii >= 1; --ii ) {
    Size swap_partner = static_cast< Size > ( std::floor( ii*rg.uniform() ));

    T temp = vect[ swap_partner ];
    vect[ swap_partner ] = vect[ ii ];
    vect[ ii ] = temp;
  }
}


template< class T >
void
random_permutation(
  std::vector< T > & vect,
  RandomGenerator & rg
)
{
  Size const vsize = vect.size();
  for ( Size ii = vsize - 1; ii >= 1; --ii ) {
    Size swap_partner = static_cast< Size > ( std::floor( ii*rg.uniform() ));

    T temp = vect[ swap_partner ];
    vect[ swap_partner ] = vect[ ii ];
    vect[ ii ] = temp;
  }
}


/// @brief randomly shuffle elements of a sequence
template< typename RandomAccessIterator >
void
random_permutation(
  RandomAccessIterator first,
  RandomAccessIterator last,
  RandomGenerator & rg
)
{
  if ( first != last ) {
    for ( RandomAccessIterator i = first + 1; i != last; ++i ) {
      std::iter_swap( i, first + static_cast< Size >( ( i - first + 1 ) * rg.uniform() ) );
    }
  }
}


} // namespace random
} // namespace numeric


#endif // INCLUDED_numeric_random_random_permutation_HH