1cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines//==- llvm/Support/RandomNumberGenerator.h - RNG for diversity ---*- C++ -*-==// 2cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// 3cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// The LLVM Compiler Infrastructure 4cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// 5cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// This file is distributed under the University of Illinois Open Source 6cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// License. See LICENSE.TXT for details. 7cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// 8cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines//===----------------------------------------------------------------------===// 9cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// 10cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// This file defines an abstraction for random number generation (RNG). 11cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// Note that the current implementation is not cryptographically secure 12cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// as it uses the C++11 <random> facilities. 13cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines// 14cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines//===----------------------------------------------------------------------===// 15cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines 16cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines#ifndef LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ 17cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines#define LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ 18cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines 19cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines#include "llvm/ADT/StringRef.h" 20cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines#include "llvm/Support/Compiler.h" 21cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines#include "llvm/Support/DataTypes.h" // Needed for uint64_t on Windows. 22cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines#include <random> 23cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines 24cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hinesnamespace llvm { 25cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines 26cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines/// A random number generator. 27cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines/// Instances of this class should not be shared across threads. 28cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hinesclass RandomNumberGenerator { 29cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hinespublic: 30cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// Seeds and salts the underlying RNG engine. The salt of type StringRef 31cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// is passed into the constructor. The seed can be set on the command 32cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// line via -rng-seed=<uint64>. 33cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// The reason for the salt is to ensure different random streams even if 34cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// the same seed is used for multiple invocations of the compiler. 35cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// A good salt value should add additional entropy and be constant across 36cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// different machines (i.e., no paths) to allow for reproducible builds. 37cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// An instance of this class can be retrieved from the current Module. 38cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// \see Module::getRNG 39cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines RandomNumberGenerator(StringRef Salt); 40cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines 41cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines /// Returns a random number in the range [0, Max). 42cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines uint64_t next(uint64_t Max); 43cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines 44cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hinesprivate: 45cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines // 64-bit Mersenne Twister by Matsumoto and Nishimura, 2000 46cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines // http://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine 47cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines std::mt19937_64 Generator; 48cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines 49cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines // Noncopyable. 50cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines RandomNumberGenerator(const RandomNumberGenerator &other) 51cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines LLVM_DELETED_FUNCTION; 52cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines RandomNumberGenerator & 53cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines operator=(const RandomNumberGenerator &other) LLVM_DELETED_FUNCTION; 54cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines}; 55cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines} 56cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines 57cd81d94322a39503e4a3e87b6ee03d4fcb3465fbStephen Hines#endif 58