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1// SPDX-License-Identifier: GPL-2.0
2#include <kunit/test.h>
3
4#include "mean_and_variance.h"
5
6#define MAX_SQR (SQRT_U64_MAX*SQRT_U64_MAX)
7
8static void mean_and_variance_basic_test(struct kunit *test)
9{
10 struct mean_and_variance s = {};
11
12 mean_and_variance_update(&s, 2);
13 mean_and_variance_update(&s, 2);
14
15 KUNIT_EXPECT_EQ(test, mean_and_variance_get_mean(s), 2);
16 KUNIT_EXPECT_EQ(test, mean_and_variance_get_variance(s), 0);
17 KUNIT_EXPECT_EQ(test, s.n, 2);
18
19 mean_and_variance_update(&s, 4);
20 mean_and_variance_update(&s, 4);
21
22 KUNIT_EXPECT_EQ(test, mean_and_variance_get_mean(s), 3);
23 KUNIT_EXPECT_EQ(test, mean_and_variance_get_variance(s), 1);
24 KUNIT_EXPECT_EQ(test, s.n, 4);
25}
26
27/*
28 * Test values computed using a spreadsheet from the psuedocode at the bottom:
29 * https://fanf2.user.srcf.net/hermes/doc/antiforgery/stats.pdf
30 */
31
32static void mean_and_variance_weighted_test(struct kunit *test)
33{
34 struct mean_and_variance_weighted s = { };
35
36 mean_and_variance_weighted_update(&s, 10, false, 2);
37 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), 10);
38 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 0);
39
40 mean_and_variance_weighted_update(&s, 20, true, 2);
41 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), 12);
42 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 18);
43
44 mean_and_variance_weighted_update(&s, 30, true, 2);
45 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), 16);
46 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 72);
47
48 s = (struct mean_and_variance_weighted) { };
49
50 mean_and_variance_weighted_update(&s, -10, false, 2);
51 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), -10);
52 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 0);
53
54 mean_and_variance_weighted_update(&s, -20, true, 2);
55 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), -12);
56 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 18);
57
58 mean_and_variance_weighted_update(&s, -30, true, 2);
59 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), -16);
60 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 72);
61}
62
63static void mean_and_variance_weighted_advanced_test(struct kunit *test)
64{
65 struct mean_and_variance_weighted s = { };
66 bool initted = false;
67 s64 i;
68
69 for (i = 10; i <= 100; i += 10) {
70 mean_and_variance_weighted_update(&s, i, initted, 8);
71 initted = true;
72 }
73
74 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 8), 11);
75 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 8), 107);
76
77 s = (struct mean_and_variance_weighted) { };
78 initted = false;
79
80 for (i = -10; i >= -100; i -= 10) {
81 mean_and_variance_weighted_update(&s, i, initted, 8);
82 initted = true;
83 }
84
85 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 8), -11);
86 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 8), 107);
87}
88
89static void do_mean_and_variance_test(struct kunit *test,
90 s64 initial_value,
91 s64 initial_n,
92 s64 n,
93 unsigned weight,
94 s64 *data,
95 s64 *mean,
96 s64 *stddev,
97 s64 *weighted_mean,
98 s64 *weighted_stddev)
99{
100 struct mean_and_variance mv = {};
101 struct mean_and_variance_weighted vw = { };
102
103 for (unsigned i = 0; i < initial_n; i++) {
104 mean_and_variance_update(&mv, initial_value);
105 mean_and_variance_weighted_update(&vw, initial_value, false, weight);
106
107 KUNIT_EXPECT_EQ(test, mean_and_variance_get_mean(mv), initial_value);
108 KUNIT_EXPECT_EQ(test, mean_and_variance_get_stddev(mv), 0);
109 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(vw, weight), initial_value);
110 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_stddev(vw, weight),0);
111 }
112
113 for (unsigned i = 0; i < n; i++) {
114 mean_and_variance_update(&mv, data[i]);
115 mean_and_variance_weighted_update(&vw, data[i], true, weight);
116
117 KUNIT_EXPECT_EQ(test, mean_and_variance_get_mean(mv), mean[i]);
118 KUNIT_EXPECT_EQ(test, mean_and_variance_get_stddev(mv), stddev[i]);
119 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(vw, weight), weighted_mean[i]);
120 KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_stddev(vw, weight),weighted_stddev[i]);
121 }
122
123 KUNIT_EXPECT_EQ(test, mv.n, initial_n + n);
124}
125
126/* Test behaviour with a single outlier, then back to steady state: */
127static void mean_and_variance_test_1(struct kunit *test)
128{
129 s64 d[] = { 100, 10, 10, 10, 10, 10, 10 };
130 s64 mean[] = { 22, 21, 20, 19, 18, 17, 16 };
131 s64 stddev[] = { 32, 29, 28, 27, 26, 25, 24 };
132 s64 weighted_mean[] = { 32, 27, 22, 19, 17, 15, 14 };
133 s64 weighted_stddev[] = { 38, 35, 31, 27, 24, 21, 18 };
134
135 do_mean_and_variance_test(test, 10, 6, ARRAY_SIZE(d), 2,
136 d, mean, stddev, weighted_mean, weighted_stddev);
137}
138
139/* Test behaviour where we switch from one steady state to another: */
140static void mean_and_variance_test_2(struct kunit *test)
141{
142 s64 d[] = { 100, 100, 100, 100, 100 };
143 s64 mean[] = { 22, 32, 40, 46, 50 };
144 s64 stddev[] = { 32, 39, 42, 44, 45 };
145 s64 weighted_mean[] = { 32, 49, 61, 71, 78 };
146 s64 weighted_stddev[] = { 38, 44, 44, 41, 38 };
147
148 do_mean_and_variance_test(test, 10, 6, ARRAY_SIZE(d), 2,
149 d, mean, stddev, weighted_mean, weighted_stddev);
150}
151
152static void mean_and_variance_fast_divpow2(struct kunit *test)
153{
154 s64 i;
155 u8 d;
156
157 for (i = 0; i < 100; i++) {
158 d = 0;
159 KUNIT_EXPECT_EQ(test, fast_divpow2(i, d), div_u64(i, 1LLU << d));
160 KUNIT_EXPECT_EQ(test, abs(fast_divpow2(-i, d)), div_u64(i, 1LLU << d));
161 for (d = 1; d < 32; d++) {
162 KUNIT_EXPECT_EQ_MSG(test, abs(fast_divpow2(i, d)),
163 div_u64(i, 1 << d), "%lld %u", i, d);
164 KUNIT_EXPECT_EQ_MSG(test, abs(fast_divpow2(-i, d)),
165 div_u64(i, 1 << d), "%lld %u", -i, d);
166 }
167 }
168}
169
170static void mean_and_variance_u128_basic_test(struct kunit *test)
171{
172 u128_u a = u64s_to_u128(0, U64_MAX);
173 u128_u a1 = u64s_to_u128(0, 1);
174 u128_u b = u64s_to_u128(1, 0);
175 u128_u c = u64s_to_u128(0, 1LLU << 63);
176 u128_u c2 = u64s_to_u128(U64_MAX, U64_MAX);
177
178 KUNIT_EXPECT_EQ(test, u128_hi(u128_add(a, a1)), 1);
179 KUNIT_EXPECT_EQ(test, u128_lo(u128_add(a, a1)), 0);
180 KUNIT_EXPECT_EQ(test, u128_hi(u128_add(a1, a)), 1);
181 KUNIT_EXPECT_EQ(test, u128_lo(u128_add(a1, a)), 0);
182
183 KUNIT_EXPECT_EQ(test, u128_lo(u128_sub(b, a1)), U64_MAX);
184 KUNIT_EXPECT_EQ(test, u128_hi(u128_sub(b, a1)), 0);
185
186 KUNIT_EXPECT_EQ(test, u128_hi(u128_shl(c, 1)), 1);
187 KUNIT_EXPECT_EQ(test, u128_lo(u128_shl(c, 1)), 0);
188
189 KUNIT_EXPECT_EQ(test, u128_hi(u128_square(U64_MAX)), U64_MAX - 1);
190 KUNIT_EXPECT_EQ(test, u128_lo(u128_square(U64_MAX)), 1);
191
192 KUNIT_EXPECT_EQ(test, u128_lo(u128_div(b, 2)), 1LLU << 63);
193
194 KUNIT_EXPECT_EQ(test, u128_hi(u128_div(c2, 2)), U64_MAX >> 1);
195 KUNIT_EXPECT_EQ(test, u128_lo(u128_div(c2, 2)), U64_MAX);
196
197 KUNIT_EXPECT_EQ(test, u128_hi(u128_div(u128_shl(u64_to_u128(U64_MAX), 32), 2)), U32_MAX >> 1);
198 KUNIT_EXPECT_EQ(test, u128_lo(u128_div(u128_shl(u64_to_u128(U64_MAX), 32), 2)), U64_MAX << 31);
199}
200
201static struct kunit_case mean_and_variance_test_cases[] = {
202 KUNIT_CASE(mean_and_variance_fast_divpow2),
203 KUNIT_CASE(mean_and_variance_u128_basic_test),
204 KUNIT_CASE(mean_and_variance_basic_test),
205 KUNIT_CASE(mean_and_variance_weighted_test),
206 KUNIT_CASE(mean_and_variance_weighted_advanced_test),
207 KUNIT_CASE(mean_and_variance_test_1),
208 KUNIT_CASE(mean_and_variance_test_2),
209 {}
210};
211
212static struct kunit_suite mean_and_variance_test_suite = {
213 .name = "mean and variance tests",
214 .test_cases = mean_and_variance_test_cases
215};
216
217kunit_test_suite(mean_and_variance_test_suite);
218
219MODULE_AUTHOR("Daniel B. Hill");
220MODULE_DESCRIPTION("bcachefs filesystem mean and variance unit tests");
221MODULE_LICENSE("GPL");