135 lines
3.8 KiB
C++
135 lines
3.8 KiB
C++
/*
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* DeterministicRandom.h
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*
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* This source file is part of the FoundationDB open source project
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*
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* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef FLOW_DETERIMINISTIC_RANDOM_H
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#define FLOW_DETERIMINISTIC_RANDOM_H
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#pragma once
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#include <cinttypes>
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#include "flow/IRandom.h"
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#include "flow/Error.h"
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#include "flow/Trace.h"
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#include "flow/FastRef.h"
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#include <random>
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class DeterministicRandom : public IRandom, public ReferenceCounted<DeterministicRandom> {
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private:
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std::mt19937 random;
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uint64_t next;
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bool useRandLog;
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uint64_t gen64() {
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uint64_t curr = next;
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next = (uint64_t(random()) << 32) ^ random();
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if (TRACE_SAMPLE()) TraceEvent(SevSample, "Random");
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return curr;
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}
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public:
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DeterministicRandom( uint32_t seed, bool useRandLog=false ) : random( (unsigned long)seed ), next( (uint64_t(random()) << 32) ^ random() ), useRandLog(useRandLog) {
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UNSTOPPABLE_ASSERT( seed != 0 ); // docs for mersenne twister say x0>0
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};
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double random01() {
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double d = gen64() / double(uint64_t(-1));
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if (randLog && useRandLog) fprintf(randLog, "R01 %f\n", d);
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return d;
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}
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int randomInt(int min, int maxPlusOne) {
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ASSERT(min < maxPlusOne);
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unsigned int range;
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if (maxPlusOne < 0)
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range = std::abs(maxPlusOne - min);
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else {
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range = maxPlusOne;
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range -= min;
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}
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uint64_t v = (gen64() % range);
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int i;
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if (min < 0 && ((unsigned int) -min) > v)
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i = -(int)(((unsigned int) -min) - v);
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else
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i = v + min;
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if (randLog && useRandLog) fprintf(randLog, "Rint %d\n", i);
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return i;
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}
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int64_t randomInt64(int64_t min, int64_t maxPlusOne) {
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ASSERT(min < maxPlusOne);
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uint64_t range;
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if (maxPlusOne < 0)
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range = std::abs(maxPlusOne - min);
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else {
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range = maxPlusOne;
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range -= min;
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}
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uint64_t v = (gen64() % range);
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int64_t i;
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if (min < 0 && ((uint64_t) -min) > v)
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i = -(int64_t)(((uint64_t) -min) - v);
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else
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i = v + min;
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if (randLog && useRandLog) fprintf(randLog, "Rint64 %" PRId64 "\n", i);
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return i;
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}
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uint32_t randomUInt32() { return gen64(); }
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uint32_t randomSkewedUInt32(uint32_t min, uint32_t maxPlusOne) {
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std::uniform_real_distribution<double> distribution( std::log(min), std::log(maxPlusOne-1) );
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double logpower = distribution(random);
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uint32_t loguniform = static_cast<uint32_t>( std::pow( 10, logpower ) );
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// doubles can be imprecise, so let's make sure we don't violate an edge case.
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return std::max(std::min(loguniform, maxPlusOne-1), min);
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}
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UID randomUniqueID() {
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uint64_t x,y;
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x = gen64();
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y = gen64();
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if (randLog && useRandLog) fprintf(randLog, "Ruid %" PRIx64 " %" PRIx64 "\n", x, y);
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return UID(x,y);
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}
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char randomAlphaNumeric() {
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static const char alphanum[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
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char c = alphanum[ gen64() % 62 ];
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if (randLog && useRandLog) fprintf(randLog, "Rchar %c\n", c);
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return c;
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}
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std::string randomAlphaNumeric( int length ) {
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std::string s;
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s.reserve( length );
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for( int i = 0; i < length; i++ )
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s += randomAlphaNumeric();
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return s;
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}
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uint64_t peek() const { return next; }
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virtual void addref() { ReferenceCounted<DeterministicRandom>::addref(); }
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virtual void delref() { ReferenceCounted<DeterministicRandom>::delref(); }
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};
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#endif
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