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