1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "suggest/core/layout/normal_distribution_2d.h"
18
19#include <gtest/gtest.h>
20
21#include <vector>
22
23namespace latinime {
24namespace {
25
26static const float ORIGIN_X = 0.0f;
27static const float ORIGIN_Y = 0.0f;
28static const float LARGE_STANDARD_DEVIATION = 100.0f;
29static const float SMALL_STANDARD_DEVIATION = 10.0f;
30static const float ZERO_RADIAN = 0.0f;
31
32TEST(NormalDistribution2DTest, ProbabilityDensity) {
33    const NormalDistribution2D distribution(ORIGIN_X, LARGE_STANDARD_DEVIATION, ORIGIN_Y,
34            SMALL_STANDARD_DEVIATION, ZERO_RADIAN);
35
36    static const float SMALL_COORDINATE = 10.0f;
37    static const float LARGE_COORDINATE = 20.0f;
38    // The probability density of the point near the distribution center is larger than the
39    // probability density of the point that is far from distribution center.
40    EXPECT_GE(distribution.getProbabilityDensity(SMALL_COORDINATE, SMALL_COORDINATE),
41            distribution.getProbabilityDensity(LARGE_COORDINATE, LARGE_COORDINATE));
42    // The probability density of the point shifted toward the direction that has larger standard
43    // deviation is larger than the probability density of the point shifted towards another
44    // direction.
45    EXPECT_GE(distribution.getProbabilityDensity(LARGE_COORDINATE, SMALL_COORDINATE),
46            distribution.getProbabilityDensity(SMALL_COORDINATE, LARGE_COORDINATE));
47}
48
49TEST(NormalDistribution2DTest, Rotate) {
50    static const float COORDINATES[] = {0.0f, 10.0f, 100.0f, -20.0f};
51    static const float EPSILON = 0.01f;
52    const NormalDistribution2D distribution(ORIGIN_X, LARGE_STANDARD_DEVIATION, ORIGIN_Y,
53            SMALL_STANDARD_DEVIATION, ZERO_RADIAN);
54    const NormalDistribution2D rotatedDistribution(ORIGIN_X, LARGE_STANDARD_DEVIATION, ORIGIN_Y,
55            SMALL_STANDARD_DEVIATION, M_PI_4);
56    for (const float x : COORDINATES) {
57        for (const float y : COORDINATES) {
58            // The probability density of the rotated distribution at the point and the probability
59            // density of the original distribution at the rotated point are the same.
60            const float probabilityDensity0 = distribution.getProbabilityDensity(x, y);
61            const float probabilityDensity1 = rotatedDistribution.getProbabilityDensity(-y, x);
62            EXPECT_NEAR(probabilityDensity0, probabilityDensity1, EPSILON);
63        }
64    }
65}
66
67}  // namespace
68}  // namespace latinime
69