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rocksdb/thrift/lib/cpp/test/loadgen/RNG.h

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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
#ifndef THRIFT_TEST_LOADGEN_RNG_H_
#define THRIFT_TEST_LOADGEN_RNG_H_ 1
#include <boost/random/mersenne_twister.hpp>
namespace apache { namespace thrift { namespace loadgen {
/**
* A random number generator to use for load tests.
*
* We keep one RNG per thread, to avoid having to perform locking when getting
* random numbers.
*
* RNG also implements the boost random number generator interface, so it can
* be used as an engine for boost random distributions.
*
*
* This class is essentially just a wrapper around boost::mt19937.
* We have to wrap it because some of the boost code copy-constructs the
* generators, causing the state of the original generator to never be updated.
* (In particular uniform_01 copy constructs its generator argument, and
* variate_generator may end up using uniform_01.)
*
* It's rather annoying that we have to define our own wrapper class for this.
*/
class RNG {
public:
// Use boost::mt19937 as the underlying RNG
typedef boost::mt19937 BoostRNG;
// result_type and has_fixed_range are required for the boost interfaces
typedef BoostRNG::result_type result_type;
static const bool has_fixed_range = false;
RNG(BoostRNG* rng) : rng_(rng) {}
/**
* Get the thread-local RNG.
*/
static RNG& getRNG();
/**
* Set the RNG seed.
*
* This value is used to pick seeds for new thread-local RNGs.
* It won't affect thread-local RNGs that have already been created.
*
* Note that that the seed value used for each thread-local RNG depends on
* the order in which the thread-local RNGs are created. You may not get
* consistent results across runs if your threads are not initialized in a
* consistent order.
*/
static void setGlobalSeed(result_type s);
/**
* Re-seed this RNG
*/
void seed(result_type s) {
rng_->seed(s);
}
/**
* Get a random number.
*
* Part of the boost random generator interface.
*/
result_type operator()() {
return (*rng_)();
}
/**
* Get the minimum value that can be returned.
*
* Part of the boost random generator interface.
*/
result_type min() const {
return rng_->min();
}
/**
* Get the maximum value that can be returned.
*
* Part of the boost random generator interface.
*/
result_type max() const {
return rng_->max();
}
/*
* Helper functions to pick random uint32_t values
*/
static uint32_t getU32();
static uint32_t getU32(uint32_t max);
static uint32_t getU32(uint32_t min, uint32_t max);
/**
* Helper function to pick random double values in the range [0.0, 1.0)
*/
static double getReal();
/**
* Helper function to pick random double values in the range [min, max)
*/
static double getReal(double min, double max);
/**
* Helper function to pick random values in a log-normal distribution.
*
* @param mean The mean value for the log-normal distribution.
* @param sigma The sigma value for the log-normal distribution.
* (This controls how spread-out the distribution will be.)
* If negative, defaults to half the mean.
*/
static double getLogNormal(double mean, double sigma = -1.0);
private:
BoostRNG* rng_;
};
}}} // apache::thrift::test
#endif // THRIFT_TEST_LOADGEN_RNG_H_