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/*
* Copyright 2008-2009 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.
*/
#include <thrust/functional.h>
#include <thrust/iterator/counting_iterator.h>
#include <thrust/iterator/transform_iterator.h>
#include <cusp/array1d.h>
#include <cstddef>
namespace cusp
{
namespace detail
{
namespace detail
{
// Integer hash functions
template <typename IndexType, typename T>
struct random_integer_functor : public thrust::unary_function<IndexType,T>
{
size_t seed;
random_integer_functor(const size_t seed)
: seed(seed) {}
// source: http://www.concentric.net/~ttwang/tech/inthash.htm
__host__ __device__
T hash(const IndexType i, thrust::detail::false_type) const
{
unsigned int h = (unsigned int) i ^ (unsigned int) seed;
h = ~h + (h << 15);
h = h ^ (h >> 12);
h = h + (h << 2);
h = h ^ (h >> 4);
h = h + (h << 3) + (h << 11);
h = h ^ (h >> 16);
return T(h);
}
__host__ __device__
T hash(const IndexType i, thrust::detail::true_type) const
{
unsigned long long h = (unsigned long long) i ^ (unsigned long long) seed;
h = ~h + (h << 21);
h = h ^ (h >> 24);
h = (h + (h << 3)) + (h << 8);
h = h ^ (h >> 14);
h = (h + (h << 2)) + (h << 4);
h = h ^ (h >> 28);
h = h + (h << 31);
return T(h);
}
__host__ __device__
T operator()(const IndexType i) const
{
return hash(i, typename thrust::detail::integral_constant<bool, sizeof(IndexType) == 8 || sizeof(T) == 8>::type());
}
};
template <typename UnsignedInteger, typename Real>
struct integer_to_real : public thrust::unary_function<UnsignedInteger,Real>
{
__host__ __device__
Real operator()(const UnsignedInteger i) const
{
const Real integer_bound = Real(UnsignedInteger(1) << (4 * sizeof(UnsignedInteger))) * Real(UnsignedInteger(1) << (4 * sizeof(UnsignedInteger)));
return Real(i) / integer_bound;
}
};
template <typename T>
struct random_integer_iterator
{
public:
typedef ptrdiff_t IndexType;
typedef typename thrust::counting_iterator<IndexType> CountingIterator;
typedef random_integer_functor<IndexType,T> Functor;
typedef typename thrust::transform_iterator<Functor, CountingIterator, T> TransformIterator;
typedef TransformIterator type;
static type make(const size_t seed)
{
return type(CountingIterator(0), Functor(seed));
}
};
template <typename T>
struct random_real_iterator
{};
template <>
struct random_real_iterator<float>
{
typedef typename random_integer_iterator<unsigned int>::type RandomIterator;
typedef integer_to_real<unsigned int, float> Functor;
typedef typename thrust::transform_iterator<Functor, RandomIterator, float> TransformIterator;
typedef TransformIterator type;
static type make(const size_t seed)
{
return type(random_integer_iterator<unsigned int>::make(seed), Functor());
}
};
template <>
struct random_real_iterator<double>
{
typedef typename random_integer_iterator<unsigned long long>::type RandomIterator;
typedef integer_to_real<unsigned long long, double> Functor;
typedef typename thrust::transform_iterator<Functor, RandomIterator, double> TransformIterator;
typedef TransformIterator type;
static type make(const size_t seed)
{
return type(random_integer_iterator<unsigned long long>::make(seed), Functor());
}
};
} // end namespace detail
/////////////////////
// Implicit Ranges //
/////////////////////
template <typename T>
class random_integers : public cusp::array1d_view<typename detail::random_integer_iterator<T>::type>
{
protected:
typedef typename detail::random_integer_iterator<T>::type Iterator;
typedef typename cusp::array1d_view<Iterator> Parent;
public:
random_integers(const size_t n, const size_t seed = 0)
: Parent(detail::random_integer_iterator<T>::make(seed),
detail::random_integer_iterator<T>::make(seed) + n)
{}
};
template <typename T>
class random_reals : public cusp::array1d_view<typename detail::random_real_iterator<T>::type>
{
protected:
typedef typename detail::random_real_iterator<T>::type Iterator;
typedef typename cusp::array1d_view<Iterator> Parent;
public:
random_reals(const size_t n, const size_t seed = 0)
: Parent(detail::random_real_iterator<T>::make(seed),
detail::random_real_iterator<T>::make(seed) + n)
{}
};
} // end namespace detail
} // end namespace cusp
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