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https://github.com/oxen-io/oxen-core.git
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8090ee3481
This adds a thread-local, pre-seeded rng at `tools::rng` (to avoid the multiple places we are creating + seeding such an RNG currently). This also moves the portable uniform value and generic shuffle code there as well as neither function is specific to service nodes and this seems a logical place for them.
61 lines
2.6 KiB
C++
61 lines
2.6 KiB
C++
// Copyright (c) 2019, The Loki Project
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//
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modification, are
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// permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice, this list of
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// conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice, this list
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// of conditions and the following disclaimer in the documentation and/or other
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// materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
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// used to endorse or promote products derived from this software without specific
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// prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#pragma once
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#include <random>
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namespace tools {
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/// A thread-local, pre-seeded mt19937_64 rng ready for use. Don't use this where an RNG with a
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/// specific seed is needed.
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extern thread_local std::mt19937_64 rng;
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/// Generates a deterministic uint64_t uniformly distributed over [0, n). This is roughly
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/// equivalent to `std::uniform_int_distribution<uint64_t>{0, n}(rng)`, but that is not guaranteed
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/// to be unique across platforms/compilers, while this is.
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uint64_t uniform_distribution_portable(std::mt19937_64& rng, uint64_t n);
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/// Uniformly shuffles all the elements in [begin, end) in a deterministic method so that, given the
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/// same seed, this will always produce the same result on any platform/compiler/etc.
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template<typename RandomIt>
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void shuffle_portable(RandomIt begin, RandomIt end, uint64_t seed)
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{
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if (end <= begin + 1) return;
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const size_t size = std::distance(begin, end);
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std::mt19937_64 rng{seed};
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for (size_t i = 1; i < size; i++)
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{
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size_t j = (size_t)uniform_distribution_portable(rng, i+1);
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using std::swap;
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swap(begin[i], begin[j]);
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}
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}
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};
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