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linux/fs/bcachefs/mean_and_variance_test.c
Darrick J. Wong 4b4f0876ab bcachefs: mean_and_variance: put struct mean_and_variance_weighted on a diet 
The only caller of this code (time_stats) always knows the weights and
whether or not any information has been collected.  Pass this
information into the mean and variance code so that it doesn't have to
store that information.  This reduces the structure size from 24 to 16
bytes, which shrinks each time_stats counter to 192 bytes from 208.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-03-13 21:37:58 -04:00

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// SPDX-License-Identifier: GPL-2.0
#include <kunit/test.h>
#include "mean_and_variance.h"
#define MAX_SQR (SQRT_U64_MAX*SQRT_U64_MAX)
static void mean_and_variance_basic_test(struct kunit *test)
{
struct mean_and_variance s = {};
mean_and_variance_update(&s, 2);
mean_and_variance_update(&s, 2);
KUNIT_EXPECT_EQ(test, mean_and_variance_get_mean(s), 2);
KUNIT_EXPECT_EQ(test, mean_and_variance_get_variance(s), 0);
KUNIT_EXPECT_EQ(test, s.n, 2);
mean_and_variance_update(&s, 4);
mean_and_variance_update(&s, 4);
KUNIT_EXPECT_EQ(test, mean_and_variance_get_mean(s), 3);
KUNIT_EXPECT_EQ(test, mean_and_variance_get_variance(s), 1);
KUNIT_EXPECT_EQ(test, s.n, 4);
}
/*
* Test values computed using a spreadsheet from the psuedocode at the bottom:
* https://fanf2.user.srcf.net/hermes/doc/antiforgery/stats.pdf
*/
static void mean_and_variance_weighted_test(struct kunit *test)
{
struct mean_and_variance_weighted s = { };
mean_and_variance_weighted_update(&s, 10, false, 2);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), 10);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 0);
mean_and_variance_weighted_update(&s, 20, true, 2);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), 12);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 18);
mean_and_variance_weighted_update(&s, 30, true, 2);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), 16);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 72);
s = (struct mean_and_variance_weighted) { };
mean_and_variance_weighted_update(&s, -10, false, 2);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), -10);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 0);
mean_and_variance_weighted_update(&s, -20, true, 2);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), -12);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 18);
mean_and_variance_weighted_update(&s, -30, true, 2);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 2), -16);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 2), 72);
}
static void mean_and_variance_weighted_advanced_test(struct kunit *test)
{
struct mean_and_variance_weighted s = { };
bool initted = false;
s64 i;
for (i = 10; i <= 100; i += 10) {
mean_and_variance_weighted_update(&s, i, initted, 8);
initted = true;
}
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 8), 11);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 8), 107);
s = (struct mean_and_variance_weighted) { };
initted = false;
for (i = -10; i >= -100; i -= 10) {
mean_and_variance_weighted_update(&s, i, initted, 8);
initted = true;
}
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s, 8), -11);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s, 8), 107);
}
static void do_mean_and_variance_test(struct kunit *test,
s64 initial_value,
s64 initial_n,
s64 n,
unsigned weight,
s64 *data,
s64 *mean,
s64 *stddev,
s64 *weighted_mean,
s64 *weighted_stddev)
{
struct mean_and_variance mv = {};
struct mean_and_variance_weighted vw = { };
for (unsigned i = 0; i < initial_n; i++) {
mean_and_variance_update(&mv, initial_value);
mean_and_variance_weighted_update(&vw, initial_value, false, weight);
KUNIT_EXPECT_EQ(test, mean_and_variance_get_mean(mv), initial_value);
KUNIT_EXPECT_EQ(test, mean_and_variance_get_stddev(mv), 0);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(vw, weight), initial_value);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_stddev(vw, weight),0);
}
for (unsigned i = 0; i < n; i++) {
mean_and_variance_update(&mv, data[i]);
mean_and_variance_weighted_update(&vw, data[i], true, weight);
KUNIT_EXPECT_EQ(test, mean_and_variance_get_mean(mv), mean[i]);
KUNIT_EXPECT_EQ(test, mean_and_variance_get_stddev(mv), stddev[i]);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(vw, weight), weighted_mean[i]);
KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_stddev(vw, weight),weighted_stddev[i]);
}
KUNIT_EXPECT_EQ(test, mv.n, initial_n + n);
}
/* Test behaviour with a single outlier, then back to steady state: */
static void mean_and_variance_test_1(struct kunit *test)
{
s64 d[] = { 100, 10, 10, 10, 10, 10, 10 };
s64 mean[] = { 22, 21, 20, 19, 18, 17, 16 };
s64 stddev[] = { 32, 29, 28, 27, 26, 25, 24 };
s64 weighted_mean[] = { 32, 27, 22, 19, 17, 15, 14 };
s64 weighted_stddev[] = { 38, 35, 31, 27, 24, 21, 18 };
do_mean_and_variance_test(test, 10, 6, ARRAY_SIZE(d), 2,
d, mean, stddev, weighted_mean, weighted_stddev);
}
static void mean_and_variance_test_2(struct kunit *test)
{
s64 d[] = { 100, 10, 10, 10, 10, 10, 10 };
s64 mean[] = { 10, 10, 10, 10, 10, 10, 10 };
s64 stddev[] = { 9, 9, 9, 9, 9, 9, 9 };
s64 weighted_mean[] = { 32, 27, 22, 19, 17, 15, 14 };
s64 weighted_stddev[] = { 38, 35, 31, 27, 24, 21, 18 };
do_mean_and_variance_test(test, 10, 6, ARRAY_SIZE(d), 2,
d, mean, stddev, weighted_mean, weighted_stddev);
}
/* Test behaviour where we switch from one steady state to another: */
static void mean_and_variance_test_3(struct kunit *test)
{
s64 d[] = { 100, 100, 100, 100, 100 };
s64 mean[] = { 22, 32, 40, 46, 50 };
s64 stddev[] = { 32, 39, 42, 44, 45 };
s64 weighted_mean[] = { 32, 49, 61, 71, 78 };
s64 weighted_stddev[] = { 38, 44, 44, 41, 38 };
do_mean_and_variance_test(test, 10, 6, ARRAY_SIZE(d), 2,
d, mean, stddev, weighted_mean, weighted_stddev);
}
static void mean_and_variance_test_4(struct kunit *test)
{
s64 d[] = { 100, 100, 100, 100, 100 };
s64 mean[] = { 10, 11, 12, 13, 14 };
s64 stddev[] = { 9, 13, 15, 17, 19 };
s64 weighted_mean[] = { 32, 49, 61, 71, 78 };
s64 weighted_stddev[] = { 38, 44, 44, 41, 38 };
do_mean_and_variance_test(test, 10, 6, ARRAY_SIZE(d), 2,
d, mean, stddev, weighted_mean, weighted_stddev);
}
static void mean_and_variance_fast_divpow2(struct kunit *test)
{
s64 i;
u8 d;
for (i = 0; i < 100; i++) {
d = 0;
KUNIT_EXPECT_EQ(test, fast_divpow2(i, d), div_u64(i, 1LLU << d));
KUNIT_EXPECT_EQ(test, abs(fast_divpow2(-i, d)), div_u64(i, 1LLU << d));
for (d = 1; d < 32; d++) {
KUNIT_EXPECT_EQ_MSG(test, abs(fast_divpow2(i, d)),
div_u64(i, 1 << d), "%lld %u", i, d);
KUNIT_EXPECT_EQ_MSG(test, abs(fast_divpow2(-i, d)),
div_u64(i, 1 << d), "%lld %u", -i, d);
}
}
}
static void mean_and_variance_u128_basic_test(struct kunit *test)
{
u128_u a = u64s_to_u128(0, U64_MAX);
u128_u a1 = u64s_to_u128(0, 1);
u128_u b = u64s_to_u128(1, 0);
u128_u c = u64s_to_u128(0, 1LLU << 63);
u128_u c2 = u64s_to_u128(U64_MAX, U64_MAX);
KUNIT_EXPECT_EQ(test, u128_hi(u128_add(a, a1)), 1);
KUNIT_EXPECT_EQ(test, u128_lo(u128_add(a, a1)), 0);
KUNIT_EXPECT_EQ(test, u128_hi(u128_add(a1, a)), 1);
KUNIT_EXPECT_EQ(test, u128_lo(u128_add(a1, a)), 0);
KUNIT_EXPECT_EQ(test, u128_lo(u128_sub(b, a1)), U64_MAX);
KUNIT_EXPECT_EQ(test, u128_hi(u128_sub(b, a1)), 0);
KUNIT_EXPECT_EQ(test, u128_hi(u128_shl(c, 1)), 1);
KUNIT_EXPECT_EQ(test, u128_lo(u128_shl(c, 1)), 0);
KUNIT_EXPECT_EQ(test, u128_hi(u128_square(U64_MAX)), U64_MAX - 1);
KUNIT_EXPECT_EQ(test, u128_lo(u128_square(U64_MAX)), 1);
KUNIT_EXPECT_EQ(test, u128_lo(u128_div(b, 2)), 1LLU << 63);
KUNIT_EXPECT_EQ(test, u128_hi(u128_div(c2, 2)), U64_MAX >> 1);
KUNIT_EXPECT_EQ(test, u128_lo(u128_div(c2, 2)), U64_MAX);
KUNIT_EXPECT_EQ(test, u128_hi(u128_div(u128_shl(u64_to_u128(U64_MAX), 32), 2)), U32_MAX >> 1);
KUNIT_EXPECT_EQ(test, u128_lo(u128_div(u128_shl(u64_to_u128(U64_MAX), 32), 2)), U64_MAX << 31);
}
static struct kunit_case mean_and_variance_test_cases[] = {
KUNIT_CASE(mean_and_variance_fast_divpow2),
KUNIT_CASE(mean_and_variance_u128_basic_test),
KUNIT_CASE(mean_and_variance_basic_test),
KUNIT_CASE(mean_and_variance_weighted_test),
KUNIT_CASE(mean_and_variance_weighted_advanced_test),
KUNIT_CASE(mean_and_variance_test_1),
KUNIT_CASE(mean_and_variance_test_2),
KUNIT_CASE(mean_and_variance_test_3),
KUNIT_CASE(mean_and_variance_test_4),
{}
};
static struct kunit_suite mean_and_variance_test_suite = {
.name = "mean and variance tests",
.test_cases = mean_and_variance_test_cases
};
kunit_test_suite(mean_and_variance_test_suite);
MODULE_AUTHOR("Daniel B. Hill");
MODULE_LICENSE("GPL");
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