libcruft-util/noise/rand.ipp

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/*
* 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.
*
* Copyright 2015 Danny Robson <danny@nerdcruft.net>
*/
#ifdef __UTIL_NOISE_RAND_IPP
#error
#endif
#define __UTIL_NOISE_RAND_IPP
#include "../hash/murmur/murmur2.hpp"
namespace util { namespace noise {
template <typename T, typename V>
T
rand (uint64_t seed, V value)
{
uint64_t accum = seed;
for (auto i: value)
accum = hash::murmur2::mix (accum, i);
T out = (accum & 0xFFFF) / T{0xFFFF};
out *= 2;
out -= 1;
return out;
}
template <size_t N, typename T, typename V>
vector<N,T>
rand (uint64_t seed, V value)
{
uint64_t accum = seed;
for (auto i: value)
accum = hash::murmur2::mix (accum, i);
vector<N,T> out;
for (auto &i: out) {
i = (accum & 0xFFFF) / T{0xFFFF};
accum = hash::murmur2::mix (accum, seed);
}
return out * 2 - 1;
}
} }