foundationdb/flow/DeterministicRandom.cpp

156 lines
4.3 KiB
C++

/*
* DeterministicRandom.cpp
*
* This source file is part of the FoundationDB open source project
*
* Copyright 2013-2022 Apple Inc. and the FoundationDB project authors
*
* Licensed 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.
*/
#include "fmt/format.h"
#include "flow/Arena.h"
#include "flow/DeterministicRandom.h"
#include <cstring>
uint64_t DeterministicRandom::gen64() {
uint64_t curr = next;
next = (uint64_t(random()) << 32) ^ random();
if (TRACE_SAMPLE())
TraceEvent(SevSample, "Random").log();
return curr;
}
DeterministicRandom::DeterministicRandom(uint32_t seed, bool useRandLog)
: random((unsigned long)seed), next((uint64_t(random()) << 32) ^ random()), useRandLog(useRandLog) {
UNSTOPPABLE_ASSERT(seed != 0); // docs for mersenne twister say x0>0
};
double DeterministicRandom::random01() {
double d = gen64() / double(uint64_t(-1));
if (randLog && useRandLog)
fprintf(randLog, "R01 %f\n", d);
return d;
}
int DeterministicRandom::randomInt(int min, int maxPlusOne) {
ASSERT(min < maxPlusOne);
unsigned int range;
if (maxPlusOne < 0)
range = std::abs(maxPlusOne - min);
else {
range = maxPlusOne;
range -= min;
}
uint64_t v = (gen64() % range);
int i;
if (min < 0 && (-static_cast<unsigned int>(min + 1)) >= v)
i = -static_cast<int>(-static_cast<unsigned int>(min + 1) - v) - 1;
else
i = v + min;
if (randLog && useRandLog)
fprintf(randLog, "Rint %d\n", i);
return i;
}
int64_t DeterministicRandom::randomInt64(int64_t min, int64_t maxPlusOne) {
ASSERT(min < maxPlusOne);
uint64_t range;
if (maxPlusOne < 0)
range = std::abs(maxPlusOne - min);
else {
range = maxPlusOne;
range -= min;
}
uint64_t v = (gen64() % range);
int64_t i;
if (min < 0 && (-static_cast<uint64_t>(min + 1)) >= v)
i = -static_cast<int64_t>(-static_cast<uint64_t>(min + 1) - v) - 1;
else
i = v + min;
if (randLog && useRandLog)
fmt::print(randLog, "Rint64 {}\n", i);
return i;
}
uint32_t DeterministicRandom::randomUInt32() {
return gen64();
}
uint64_t DeterministicRandom::randomUInt64() {
return gen64();
}
uint32_t DeterministicRandom::randomSkewedUInt32(uint32_t min, uint32_t maxPlusOne) {
ASSERT(min < maxPlusOne);
std::uniform_real_distribution<double> distribution(std::log(std::max<double>(min, 1.0 / M_E)),
std::log(maxPlusOne));
double exponent = distribution(random);
uint32_t value = static_cast<uint32_t>(std::pow(M_E, exponent));
return std::max(std::min(value, maxPlusOne - 1), min);
}
UID DeterministicRandom::randomUniqueID() {
uint64_t x, y;
x = gen64();
y = gen64();
if (randLog && useRandLog)
fmt::print(randLog, "Ruid {0} {1}\n", x, y);
return UID(x, y);
}
char DeterministicRandom::randomAlphaNumeric() {
static const char alphanum[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
char c = alphanum[gen64() % 62];
if (randLog && useRandLog)
fprintf(randLog, "Rchar %c\n", c);
return c;
}
std::string DeterministicRandom::randomAlphaNumeric(int length) {
std::string s;
s.reserve(length);
for (int i = 0; i < length; i++)
s += randomAlphaNumeric();
return s;
}
void DeterministicRandom::randomBytes(uint8_t* buf, int length) {
constexpr const int unitLen = sizeof(decltype(gen64()));
for (int i = 0; i < length; i += unitLen) {
auto val = gen64();
memcpy(buf + i, &val, std::min(unitLen, length - i));
}
if (randLog && useRandLog) {
constexpr const int cutOff = 32;
bool tooLong = length > cutOff;
fmt::print(randLog,
"Rbytes[{}] {}{}\n",
length,
StringRef(buf, std::min(cutOff, length)).printable(),
tooLong ? "..." : "");
}
}
uint64_t DeterministicRandom::peek() const {
return next;
}
void DeterministicRandom::addref() {
ReferenceCounted<DeterministicRandom>::addref();
}
void DeterministicRandom::delref() {
ReferenceCounted<DeterministicRandom>::delref();
}