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/*
* Copyright 2008-2013 NVIDIA Corporation
*
* 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.
*/
/*! \file discard_block_engine.h
* \brief A random number engine which adapts a base engine and produces
* numbers by discarding all but a contiguous blocks of its values.
*/
#pragma once
#include <thrust/detail/config.h>
#include <thrust/detail/config.h>
#include <iostream>
#include <thrust/detail/cstdint.h>
#include <thrust/random/detail/random_core_access.h>
THRUST_NAMESPACE_BEGIN
namespace random
{
/*! \addtogroup random_number_engine_adaptors Random Number Engine Adaptor Class Templates
* \ingroup random
* \{
*/
/*! \class discard_block_engine
* \brief A \p discard_block_engine adapts an existing base random number engine and produces
* random values by discarding some of the values returned by its base engine.
* Each cycle of the compound engine begins by returning \c r values successively produced
* by the base engine and ends by discarding <tt>p-r</tt> such values. The engine's state
* is the state of its base engine followed by the number of calls to <tt>operator()</tt>
* that have occurred since the beginning of the current cycle.
*
* \tparam Engine The type of the base random number engine to adapt.
* \tparam p The discard cycle length.
* \tparam r The number of values to return of the base engine. Because <tt>p-r</tt> will be
* discarded, <tt>r <= p</tt>.
*
* The following code snippet shows an example of using a \p discard_block_engine instance:
*
* \code
* #include <thrust/random/linear_congruential_engine.h>
* #include <thrust/random/discard_block_engine.h>
* #include <iostream>
*
* int main(void)
* {
* // create a discard_block_engine from minstd_rand, with a cycle length of 13
* // keep every first 10 values, and discard the next 3
* thrust::discard_block_engine<thrust::minstd_rand, 13, 10> rng;
*
* // print a random number to standard output
* std::cout << rng() << std::endl;
*
* return 0;
* }
* \endcode
*/
template<typename Engine, size_t p, size_t r>
class discard_block_engine
{
public:
// types
/*! \typedef base_type
* \brief The type of the adapted base random number engine.
*/
typedef Engine base_type;
/*! \typedef result_type
* \brief The type of the unsigned integer produced by this \p linear_congruential_engine.
*/
typedef typename base_type::result_type result_type;
// engine characteristics
/*! The length of the production cycle.
*/
static const size_t block_size = p;
/*! The number of used numbers per production cycle.
*/
static const size_t used_block = r;
/*! The smallest value this \p discard_block_engine may potentially produce.
*/
static const result_type min = base_type::min;
/*! The largest value this \p discard_block_engine may potentially produce.
*/
static const result_type max = base_type::max;
// constructors and seeding functions
/*! This constructor constructs a new \p discard_block_engine and constructs
* its \p base_type engine using its null constructor.
*/
__host__ __device__
discard_block_engine();
/*! This constructor constructs a new \p discard_block_engine using
* a given \p base_type engine to initialize its adapted base engine.
*
* \param urng A \p base_type to use to initialize this \p discard_block_engine's
* adapted base engine.
*/
__host__ __device__
explicit discard_block_engine(const base_type &urng);
/*! This constructor initializes a new \p discard_block_engine with a given seed.
*
* \param s The seed used to intialize this \p discard_block_engine's adapted base engine.
*/
__host__ __device__
explicit discard_block_engine(result_type s);
/*! This method initializes the state of this \p discard_block_engine's adapted base engine
* by using its \p default_seed value.
*/
__host__ __device__
void seed(void);
/*! This method initializes the state of this \p discard_block_engine's adapted base engine
* by using the given seed.
*
* \param s The seed with which to intialize this \p discard_block_engine's adapted base engine.
*/
__host__ __device__
void seed(result_type s);
// generating functions
/*! This member function produces a new random value and updates this \p discard_block_engine's state.
* \return A new random number.
*/
__host__ __device__
result_type operator()(void);
/*! This member function advances this \p discard_block_engine's state a given number of times
* and discards the results.
*
* \param z The number of random values to discard.
* \note This function is provided because an implementation may be able to accelerate it.
*/
__host__ __device__
void discard(unsigned long long z);
// property functions
/*! This member function returns a const reference to this \p discard_block_engine's
* adapted base engine.
*
* \return A const reference to the base engine this \p discard_block_engine adapts.
*/
__host__ __device__
const base_type &base(void) const;
/*! \cond
*/
private:
base_type m_e;
unsigned int m_n;
friend struct thrust::random::detail::random_core_access;
__host__ __device__
bool equal(const discard_block_engine &rhs) const;
template<typename CharT, typename Traits>
std::basic_ostream<CharT,Traits>& stream_out(std::basic_ostream<CharT,Traits> &os) const;
template<typename CharT, typename Traits>
std::basic_istream<CharT,Traits>& stream_in(std::basic_istream<CharT,Traits> &is);
/*! \endcond
*/
}; // end discard_block_engine
/*! This function checks two \p discard_block_engines for equality.
* \param lhs The first \p discard_block_engine to test.
* \param rhs The second \p discard_block_engine to test.
* \return \c true if \p lhs is equal to \p rhs; \c false, otherwise.
*/
template<typename Engine, size_t p, size_t r>
__host__ __device__
bool operator==(const discard_block_engine<Engine,p,r> &lhs,
const discard_block_engine<Engine,p,r> &rhs);
/*! This function checks two \p discard_block_engines for inequality.
* \param lhs The first \p discard_block_engine to test.
* \param rhs The second \p discard_block_engine to test.
* \return \c true if \p lhs is not equal to \p rhs; \c false, otherwise.
*/
template<typename Engine, size_t p, size_t r>
__host__ __device__
bool operator!=(const discard_block_engine<Engine,p,r> &lhs,
const discard_block_engine<Engine,p,r> &rhs);
/*! This function streams a discard_block_engine to a \p std::basic_ostream.
* \param os The \p basic_ostream to stream out to.
* \param e The \p discard_block_engine to stream out.
* \return \p os
*/
template<typename Engine, size_t p, size_t r,
typename CharT, typename Traits>
std::basic_ostream<CharT,Traits>&
operator<<(std::basic_ostream<CharT,Traits> &os,
const discard_block_engine<Engine,p,r> &e);
/*! This function streams a discard_block_engine in from a std::basic_istream.
* \param is The \p basic_istream to stream from.
* \param e The \p discard_block_engine to stream in.
* \return \p is
*/
template<typename Engine, size_t p, size_t r,
typename CharT, typename Traits>
std::basic_istream<CharT,Traits>&
operator>>(std::basic_istream<CharT,Traits> &is,
discard_block_engine<Engine,p,r> &e);
/*! \} // end random_number_engine_adaptors
*/
} // end random
// import names into thrust::
using random::discard_block_engine;
THRUST_NAMESPACE_END
#include <thrust/random/detail/discard_block_engine.inl>
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