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/*
* Copyright (C) 2013 The Android Open Source Project
*
* 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.
*/
#ifndef LATINIME_SUGGEST_UTILS_H
#define LATINIME_SUGGEST_UTILS_H
#include "defines.h"
#include "proximity_info_params.h"
namespace latinime {
class SuggestUtils {
public:
static float getDistanceScalingFactor(const float normalizedSquaredDistance) {
if (normalizedSquaredDistance < 0.0f) {
return -1.0f;
}
// Promote or demote the score according to the distance from the sweet spot
static const float A = ZERO_DISTANCE_PROMOTION_RATE / 100.0f;
static const float B = 1.0f;
static const float C = 0.5f;
static const float MIN = 0.3f;
static const float R1 = NEUTRAL_SCORE_SQUARED_RADIUS;
static const float R2 = HALF_SCORE_SQUARED_RADIUS;
const float x = normalizedSquaredDistance / static_cast<float>(
ProximityInfoParams::NORMALIZED_SQUARED_DISTANCE_SCALING_FACTOR);
const float factor = max((x < R1)
? (A * (R1 - x) + B * x) / R1
: (B * (R2 - x) + C * (x - R1)) / (R2 - R1), MIN);
// factor is a piecewise linear function like:
// A -_ .
// ^-_ .
// B \ .
// \_ .
// C ------------.
// .
// 0 R1 R2 .
return factor;
}
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(SuggestUtils);
};
} // namespace latinime
#endif // LATINIME_SUGGEST_UTILS_H
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