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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/browser/metrics/perf/random_selector.h"
#include <ostream>
#include "base/check_op.h"
#include "base/notreached.h"
#include "base/rand_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_split.h"
#include "base/strings/string_util.h"
RandomSelector::RandomSelector() : sum_of_weights_(0) {}
RandomSelector::~RandomSelector() = default;
// static
double RandomSelector::SumWeights(const std::vector<WeightAndValue>& odds) {
double sum = 0.0;
for (const auto& odd : odds) {
if (odd.weight <= 0.0)
return -1.0;
sum += odd.weight;
}
return sum;
}
bool RandomSelector::SetOdds(const std::vector<WeightAndValue>& odds) {
double sum = SumWeights(odds);
if (sum <= 0.0)
return false;
odds_ = odds;
sum_of_weights_ = sum;
return true;
}
const std::string& RandomSelector::Select() {
// Get a random double between 0 and the sum.
double random = RandDoubleUpTo(sum_of_weights_);
// Figure out what it belongs to.
return GetValueFor(random);
}
double RandomSelector::RandDoubleUpTo(double max) {
CHECK_GT(max, 0.0);
return max * base::RandDouble();
}
const std::string& RandomSelector::GetValueFor(double random) {
double current = 0.0;
for (const auto& odd : odds_) {
current += odd.weight;
if (random < current)
return odd.value;
}
NOTREACHED() << "Invalid value for key: " << random;
}
// Print the value. Used for friendly test failure messages.
::std::ostream& operator<<(
::std::ostream& os, const RandomSelector::WeightAndValue& value) {
return os << "{" << value.weight << ", \"" << value.value << "\"}";
}
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