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