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/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2018 Claire Xenia Wolf <claire@yosyshq.com>
* Copyright (C) 2018 Serge Bazanski <q3k@q3k.org>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#ifndef DETERMINISTIC_RNG_H
#define DETERMINISTIC_RNG_H
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <vector>
#include "nextpnr_namespaces.h"
NEXTPNR_NAMESPACE_BEGIN
struct DeterministicRNG
{
uint64_t rngstate;
DeterministicRNG() : rngstate(0x3141592653589793) {}
uint64_t rng64()
{
// xorshift64star
// https://arxiv.org/abs/1402.6246
uint64_t retval = rngstate * 0x2545F4914F6CDD1D;
rngstate ^= rngstate >> 12;
rngstate ^= rngstate << 25;
rngstate ^= rngstate >> 27;
return retval;
}
int rng() { return rng64() & 0x3fffffff; }
int rng(int n)
{
assert(n > 0);
// round up to power of 2
int m = n - 1;
m |= (m >> 1);
m |= (m >> 2);
m |= (m >> 4);
m |= (m >> 8);
m |= (m >> 16);
m += 1;
while (1) {
int x = rng64() & (m - 1);
if (x < n)
return x;
}
}
void rngseed(uint64_t seed)
{
rngstate = seed ? seed : 0x3141592653589793;
for (int i = 0; i < 5; i++)
rng64();
}
template <typename Iter> void shuffle(const Iter &begin, const Iter &end)
{
std::size_t size = end - begin;
for (std::size_t i = 0; i != size; i++) {
std::size_t j = i + rng(size - i);
if (j > i)
std::swap(*(begin + i), *(begin + j));
}
}
template <typename T> void shuffle(std::vector<T> &a) { shuffle(a.begin(), a.end()); }
template <typename T> void sorted_shuffle(std::vector<T> &a)
{
std::sort(a.begin(), a.end());
shuffle(a);
}
};
NEXTPNR_NAMESPACE_END
#endif
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