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325 lines
7.7 KiB
325 lines
7.7 KiB
11 years ago
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/*
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* Copyright 2008-2012 NVIDIA Corporation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <thrust/detail/type_traits.h>
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#include <thrust/detail/mpl/math.h>
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#include <limits>
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#include <cstddef>
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namespace thrust
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{
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namespace random
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{
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namespace detail
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{
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namespace math = thrust::detail::mpl::math;
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namespace detail
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{
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// two cases for this function avoids compile-time warnings of overflow
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template<typename UIntType, UIntType w,
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UIntType lhs, UIntType rhs,
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bool shift_will_overflow>
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struct lshift_w
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{
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static const UIntType value = 0;
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};
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template<typename UIntType, UIntType w,
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UIntType lhs, UIntType rhs>
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struct lshift_w<UIntType,w,lhs,rhs,false>
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{
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static const UIntType value = lhs << rhs;
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};
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} // end detail
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template<typename UIntType, UIntType w,
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UIntType lhs, UIntType rhs>
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struct lshift_w
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{
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static const bool shift_will_overflow = rhs >= w;
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static const UIntType value = detail::lshift_w<UIntType, w, lhs, rhs, shift_will_overflow>::value;
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};
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template<typename UIntType, UIntType lhs, UIntType rhs>
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struct lshift
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: lshift_w<UIntType, std::numeric_limits<UIntType>::digits, lhs, rhs>
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{};
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template<typename UIntType, int p>
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struct two_to_the_power
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: lshift<UIntType, 1, p>
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{};
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template<typename result_type, result_type a, result_type b, int d>
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class xor_combine_engine_max_aux_constants
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{
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public:
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static const result_type two_to_the_d = two_to_the_power<result_type, d>::value;
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static const result_type c = lshift<result_type, a, d>::value;
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static const result_type t =
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math::max<
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result_type,
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c,
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b
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>::value;
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static const result_type u =
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math::min<
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result_type,
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c,
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b
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>::value;
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static const result_type p = math::log2<u>::value;
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static const result_type two_to_the_p = two_to_the_power<result_type, p>::value;
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static const result_type k = math::div<result_type, t, two_to_the_p>::value;
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};
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template<typename result_type, result_type, result_type, int> struct xor_combine_engine_max_aux;
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template<typename result_type, result_type a, result_type b, int d>
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struct xor_combine_engine_max_aux_case4
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{
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typedef xor_combine_engine_max_aux_constants<result_type,a,b,d> constants;
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static const result_type k_plus_1_times_two_to_the_p =
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lshift<
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result_type,
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math::plus<result_type,constants::k,1>::value,
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constants::p
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>::value;
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static const result_type M =
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xor_combine_engine_max_aux<
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result_type,
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math::div<
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result_type,
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math::mod<
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result_type,
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constants::u,
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constants::two_to_the_p
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>::value,
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constants::two_to_the_p
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>::value,
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math::mod<
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result_type,
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constants::t,
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constants::two_to_the_p
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>::value,
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d
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>::value;
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static const result_type value = math::plus<result_type, k_plus_1_times_two_to_the_p, M>::value;
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};
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template<typename result_type, result_type a, result_type b, int d>
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struct xor_combine_engine_max_aux_case3
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{
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typedef xor_combine_engine_max_aux_constants<result_type,a,b,d> constants;
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static const result_type k_plus_1_times_two_to_the_p =
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lshift<
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result_type,
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math::plus<result_type,constants::k,1>::value,
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constants::p
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>::value;
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static const result_type M =
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xor_combine_engine_max_aux<
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result_type,
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math::div<
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result_type,
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math::mod<
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result_type,
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constants::t,
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constants::two_to_the_p
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>::value,
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constants::two_to_the_p
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>::value,
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math::mod<
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result_type,
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constants::u,
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constants::two_to_the_p
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>::value,
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d
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>::value;
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static const result_type value = math::plus<result_type, k_plus_1_times_two_to_the_p, M>::value;
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};
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template<typename result_type, result_type a, result_type b, int d>
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struct xor_combine_engine_max_aux_case2
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{
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typedef xor_combine_engine_max_aux_constants<result_type,a,b,d> constants;
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static const result_type k_plus_1_times_two_to_the_p =
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lshift<
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result_type,
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math::plus<result_type,constants::k,1>::value,
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constants::p
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>::value;
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static const result_type value =
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math::minus<
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result_type,
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k_plus_1_times_two_to_the_p,
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1
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>::value;
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};
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template<typename result_type, result_type a, result_type b, int d>
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struct xor_combine_engine_max_aux_case1
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{
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static const result_type c = lshift<result_type, a, d>::value;
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static const result_type value = math::plus<result_type,c,b>::value;
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};
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template<typename result_type, result_type a, result_type b, int d>
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struct xor_combine_engine_max_aux_2
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{
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typedef xor_combine_engine_max_aux_constants<result_type,a,b,d> constants;
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static const result_type value =
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thrust::detail::eval_if<
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// if k is odd...
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math::is_odd<result_type, constants::k>::value,
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thrust::detail::identity_<
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thrust::detail::integral_constant<
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result_type,
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xor_combine_engine_max_aux_case2<result_type,a,b,d>::value
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>
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>,
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thrust::detail::eval_if<
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// otherwise if a * 2^3 >= b, then case 3
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a * constants::two_to_the_d >= b,
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thrust::detail::identity_<
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thrust::detail::integral_constant<
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result_type,
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xor_combine_engine_max_aux_case3<result_type,a,b,d>::value
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>
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>,
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// otherwise, case 4
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thrust::detail::identity_<
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thrust::detail::integral_constant<
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result_type,
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xor_combine_engine_max_aux_case4<result_type,a,b,d>::value
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>
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>
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>
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>::type::value;
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};
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template<typename result_type,
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result_type a,
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result_type b,
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int d,
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bool use_case1 = (a == 0) || (b < two_to_the_power<result_type,d>::value)>
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struct xor_combine_engine_max_aux_1
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: xor_combine_engine_max_aux_case1<result_type,a,b,d>
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{};
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template<typename result_type,
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result_type a,
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result_type b,
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int d>
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struct xor_combine_engine_max_aux_1<result_type,a,b,d,false>
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: xor_combine_engine_max_aux_2<result_type,a,b,d>
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{};
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template<typename result_type,
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result_type a,
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result_type b,
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int d>
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struct xor_combine_engine_max_aux
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: xor_combine_engine_max_aux_1<result_type,a,b,d>
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{};
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template<typename Engine1, size_t s1, typename Engine2, size_t s2, typename result_type>
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struct xor_combine_engine_max
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{
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static const size_t w = std::numeric_limits<result_type>::digits;
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static const result_type m1 =
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math::min<
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result_type,
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result_type(Engine1::max - Engine1::min),
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two_to_the_power<result_type, w-s1>::value - 1
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>::value;
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static const result_type m2 =
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math::min<
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result_type,
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result_type(Engine2::max - Engine2::min),
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two_to_the_power<result_type, w-s2>::value - 1
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>::value;
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static const result_type s = s1 - s2;
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static const result_type M =
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xor_combine_engine_max_aux<
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result_type,
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m1,
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m2,
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s
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>::value;
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// the value is M(m1,m2,s) lshift_w s2
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static const result_type value =
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lshift_w<
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result_type,
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w,
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M,
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s2
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>::value;
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}; // end xor_combine_engine_max
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} // end detail
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} // end random
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} // end thrust
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