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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351636 91177308-0d34-0410-b5e6-96231b3b80d8
97 lines
3.1 KiB
C++
97 lines
3.1 KiB
C++
//===--- Random.h - Utilities for random sampling -------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Utilities for random sampling.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_FUZZMUTATE_RANDOM_H
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#define LLVM_FUZZMUTATE_RANDOM_H
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#include <random>
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#include "llvm/Support/raw_ostream.h"
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namespace llvm {
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/// Return a uniformly distributed random value between \c Min and \c Max
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template <typename T, typename GenT> T uniform(GenT &Gen, T Min, T Max) {
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return std::uniform_int_distribution<T>(Min, Max)(Gen);
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}
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/// Return a uniformly distributed random value of type \c T
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template <typename T, typename GenT> T uniform(GenT &Gen) {
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return uniform<T>(Gen, std::numeric_limits<T>::min(),
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std::numeric_limits<T>::max());
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}
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/// Randomly selects an item by sampling into a set with an unknown number of
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/// elements, which may each be weighted to be more likely choices.
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template <typename T, typename GenT> class ReservoirSampler {
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GenT &RandGen;
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typename std::remove_const<T>::type Selection = {};
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uint64_t TotalWeight = 0;
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public:
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ReservoirSampler(GenT &RandGen) : RandGen(RandGen) {}
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uint64_t totalWeight() const { return TotalWeight; }
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bool isEmpty() const { return TotalWeight == 0; }
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const T &getSelection() const {
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assert(!isEmpty() && "Nothing selected");
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return Selection;
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}
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explicit operator bool() const { return !isEmpty();}
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const T &operator*() const { return getSelection(); }
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/// Sample each item in \c Items with unit weight
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template <typename RangeT> ReservoirSampler &sample(RangeT &&Items) {
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for (auto &I : Items)
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sample(I, 1);
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return *this;
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}
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/// Sample a single item with the given weight.
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ReservoirSampler &sample(const T &Item, uint64_t Weight) {
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if (!Weight)
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// If the weight is zero, do nothing.
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return *this;
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TotalWeight += Weight;
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// Consider switching from the current element to this one.
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if (uniform<uint64_t>(RandGen, 1, TotalWeight) <= Weight)
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Selection = Item;
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return *this;
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}
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};
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template <typename GenT, typename RangeT,
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typename ElT = typename std::remove_reference<
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decltype(*std::begin(std::declval<RangeT>()))>::type>
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ReservoirSampler<ElT, GenT> makeSampler(GenT &RandGen, RangeT &&Items) {
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ReservoirSampler<ElT, GenT> RS(RandGen);
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RS.sample(Items);
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return RS;
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}
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template <typename GenT, typename T>
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ReservoirSampler<T, GenT> makeSampler(GenT &RandGen, const T &Item,
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uint64_t Weight) {
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ReservoirSampler<T, GenT> RS(RandGen);
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RS.sample(Item, Weight);
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return RS;
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}
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template <typename T, typename GenT>
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ReservoirSampler<T, GenT> makeSampler(GenT &RandGen) {
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return ReservoirSampler<T, GenT>(RandGen);
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}
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} // End llvm namespace
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#endif // LLVM_FUZZMUTATE_RANDOM_H
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