ceph/src/boost/boost/compute/algorithm/stable_partition.hpp

   1 //---------------------------------------------------------------------------//
   2 // Copyright (c) 2014 Roshan <thisisroshansmail@gmail.com>
   3 //
   4 // Distributed under the Boost Software License, Version 1.0
   5 // See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt
   7 //
   8 // See http://boostorg.github.com/compute for more information.
   9 //---------------------------------------------------------------------------//
  10
  11 #ifndef BOOST_COMPUTE_ALGORITHM_STABLE_PARTITION_HPP
  12 #define BOOST_COMPUTE_ALGORITHM_STABLE_PARTITION_HPP
  13
  14 #include <boost/compute/system.hpp>
  15 #include <boost/compute/context.hpp>
  16 #include <boost/compute/functional.hpp>
  17 #include <boost/compute/command_queue.hpp>
  18 #include <boost/compute/algorithm/copy_if.hpp>
  19 #include <boost/compute/container/vector.hpp>
  20
  21 namespace boost {
  22 namespace compute {
  23
  24 ///
  25 /// \brief Partitioning algorithm
  26 ///
  27 /// Partitions the elements in the range [\p first, \p last) according to
  28 /// \p predicate. The order of the elements is preserved.
  29 /// \return Iterator pointing to end of true values
  30 ///
  31 /// \param first Iterator pointing to start of range
  32 /// \param last Iterator pointing to end of range
  33 /// \param predicate Unary predicate to be applied on each element
  34 /// \param queue Queue on which to execute
  35 ///
  36 /// Space complexity: \Omega(3n)
  37 ///
  38 /// \see is_partitioned() and partition()
  39 ///
  40 template<class Iterator, class UnaryPredicate>
  41 inline Iterator stable_partition(Iterator first,
  42                                  Iterator last,
  43                                  UnaryPredicate predicate,
  44                                  command_queue &queue = system::default_queue())
  45 {
  46     typedef typename std::iterator_traits<Iterator>::value_type value_type;
  47
  48     // make temporary copy of the input
  49     ::boost::compute::vector<value_type> tmp(first, last, queue);
  50
  51     // copy true values
  52     Iterator last_true =
  53         ::boost::compute::copy_if(tmp.begin(),
  54                                   tmp.end(),
  55                                   first,
  56                                   predicate,
  57                                   queue);
  58
  59     // copy false values
  60     Iterator last_false =
  61         ::boost::compute::copy_if(tmp.begin(),
  62                                   tmp.end(),
  63                                   last_true,
  64                                   not1(predicate),
  65                                   queue);
  66
  67     // return iterator pointing to the last true value
  68     return last_true;
  69 }
  70
  71 } // end compute namespace
  72 } // end boost namespace
  73
  74 #endif // BOOST_COMPUTE_ALGORITHM_STABLE_PARTITION_HPP