fs/bcachefs/mean_and_variance_test.c

   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
   8 static 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
  32 static 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
  63 static 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
  89 static 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: */
 127 static 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: */
 140 static 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
 152 static 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
 170 static 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
 201 static 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
 212 static struct kunit_suite mean_and_variance_test_suite = {
 213         .name           = "mean and variance tests",
 214         .test_cases     = mean_and_variance_test_cases
 215 };
 216
 217 kunit_test_suite(mean_and_variance_test_suite);
 218
 219 MODULE_AUTHOR("Daniel B. Hill");
 220 MODULE_DESCRIPTION("bcachefs filesystem mean and variance unit tests");
 221 MODULE_LICENSE("GPL");