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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MEDIA_LEARNING_COMMON_TARGET_HISTOGRAM_H_
#define MEDIA_LEARNING_COMMON_TARGET_HISTOGRAM_H_
#include <ostream>
#include <string>
#include "base/component_export.h"
#include "base/containers/flat_map.h"
#include "base/macros.h"
#include "media/learning/common/labelled_example.h"
#include "media/learning/common/value.h"
#include "mojo/public/cpp/bindings/struct_traits.h" // nogncheck
namespace media {
namespace learning {
namespace mojom {
class TargetHistogramDataView;
}
// Intermediate type for mojom struct traits translation.
// See learning_types.mojom.
struct COMPONENT_EXPORT(LEARNING_COMMON) TargetHistogramPair {
TargetValue target_value;
double count;
};
// Histogram of target values that allows fractional counts.
class COMPONENT_EXPORT(LEARNING_COMMON) TargetHistogram {
public:
// We use a flat_map since this will often have only one or two TargetValues,
// such as "true" or "false".
using CountMap = base::flat_map<TargetValue, double>;
TargetHistogram();
TargetHistogram(const TargetHistogram& rhs);
TargetHistogram(TargetHistogram&& rhs);
~TargetHistogram();
TargetHistogram& operator=(const TargetHistogram& rhs);
TargetHistogram& operator=(TargetHistogram&& rhs);
bool operator==(const TargetHistogram& rhs) const;
// Add |rhs| to our counts.
TargetHistogram& operator+=(const TargetHistogram& rhs);
// Increment |rhs| by one.
TargetHistogram& operator+=(const TargetValue& rhs);
// Increment the histogram by |example|'s target value and weight.
TargetHistogram& operator+=(const LabelledExample& example);
// Return the number of counts for |value|.
double operator[](const TargetValue& value) const;
double& operator[](const TargetValue& value);
// Return the total counts in the map.
double total_counts() const {
double total = 0.;
for (auto& entry : counts_)
total += entry.second;
return total;
}
CountMap::const_iterator begin() const { return counts_.begin(); }
CountMap::const_iterator end() const { return counts_.end(); }
// Return the number of buckets in the histogram.
// TODO(liberato): Do we want this?
size_t size() const { return counts_.size(); }
// Find the singular value with the highest counts, and copy it into
// |value_out| and (optionally) |counts_out|. Returns true if there is a
// singular maximum, else returns false with the out params undefined.
bool FindSingularMax(TargetValue* value_out,
double* counts_out = nullptr) const;
// Return the average value of the entries in this histogram. Of course,
// this only makes sense if the TargetValues can be interpreted as numeric.
double Average() const;
// Normalize the histogram so that it has one total count, unless it's
// empty. It will continue to have zero in that case.
void Normalize();
std::string ToString() const;
private:
friend struct mojo::StructTraits<
media::learning::mojom::TargetHistogramDataView,
media::learning::TargetHistogram>;
const CountMap& counts() const { return counts_; }
// [value] == counts
CountMap counts_;
// Allow copy and assign.
};
COMPONENT_EXPORT(LEARNING_COMMON)
std::ostream& operator<<(std::ostream& out, const TargetHistogram& dist);
} // namespace learning
} // namespace media
#endif // MEDIA_LEARNING_COMMON_TARGET_HISTOGRAM_H_
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