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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.
#include "base/callback.h"
#include "base/component_export.h"
#include "base/macros.h"
#include "media/learning/common/labelled_example.h"
#include "media/learning/common/learning_task.h"
namespace media {
namespace learning {
// Client for a single learning task. Intended to be the primary API for client
// code that generates FeatureVectors / requests predictions for a single task.
// The API supports sending in an observed FeatureVector without a target value,
// so that framework-provided features (FeatureProvider) can be snapshotted at
// the right time. One doesn't generally want to wait until the TargetValue is
// observed to do that.
class COMPONENT_EXPORT(LEARNING_COMMON) LearningTaskController {
LearningTaskController() = default;
virtual ~LearningTaskController() = default;
// Used to set the target value and example weight.
using SetTargetValueCB = base::OnceCallback<void(TargetValue, WeightType)>;
// Record a FeatureVector that may be used for prediction and / or adding a
// new example. Call this at the time one would try to predict the
// TargetValue. This lets the framework snapshot any framework-provided
// feature values at prediction time. Later, if you want to turn these
// features into an example for training a model, then call the returned CB
// with the TargetValue and weight. Otherwise, you may discard the CB.
// TODO(liberato): This should optionally take a callback to receive a
// prediction for the FeatureVector.
// TODO(liberato): See if this ends up generating smaller code with pass-by-
// value or with |FeatureVector&&|, once we have callers that can actually
// benefit from it.
virtual SetTargetValueCB BeginObservation(const FeatureVector& features) = 0;
} // namespace learning
} // namespace media