75 lines
2.1 KiB
C++
75 lines
2.1 KiB
C++
/*
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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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* Copyright 2015 Danny Robson <danny@nerdcruft.net>
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*/
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#ifdef __UTIL_NOISE_RAND_HASH_IPP
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#error
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#endif
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#define __UTIL_NOISE_RAND_HASH_IPP
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namespace util { namespace noise { namespace rand {
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//-------------------------------------------------------------------------
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template <
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typename U,
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size_t S,
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typename T,
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template <size_t,typename> class Q
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>
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U
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hash::scalar (uint64_t seed, Q<S,T> query) noexcept
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{
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constexpr decltype(seed) BITS = 0xFFFF;
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static_assert (std::is_integral<T>::value,
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"mixing only works on integral types");
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uint64_t accum = seed;
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for (auto i: query)
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accum = util::hash::murmur2::mix (accum, i);
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return (accum & BITS) / U{BITS};
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}
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//-------------------------------------------------------------------------
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template <
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template <size_t,typename> class R,
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typename U,
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size_t S,
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typename T,
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template <size_t,typename> class Q
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>
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R<S,U>
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hash::coord (uint64_t seed, Q<S,T> query) noexcept
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{
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constexpr decltype(seed) PERTURB = 0x96c39996c36c36c3;
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constexpr decltype(seed) BITS = 0xFFFF;
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auto accum = seed ^ PERTURB;
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for (auto i: query)
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accum = util::hash::murmur2::mix (accum, i);
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R<S,U> result;
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for (auto &i: result) {
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i = (accum & BITS);
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i /= BITS;
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accum = util::hash::murmur2::mix (accum, seed);
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}
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return result;
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}
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} } }
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