Commit 65bc4109 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

mean and variance: More tests 



Add some more tests that test conventional and weighted mean
simultaneously, and with a table of values that represents events that
we'll be using this to look for so we can verify-by-eyeball that the
output looks sane.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent aab5e097

fs/bcachefs/mean_and_variance.h

+6 −8
Original line number Diff line number Diff line
@@ -176,14 +176,12 @@ static inline s64 fast_divpow2(s64 n, u8 d) 
 *

 * see linked pdf equation 12.

 */

static inline struct mean_and_variance

mean_and_variance_update(struct mean_and_variance s, s64 v)

static inline void

mean_and_variance_update(struct mean_and_variance *s, s64 v)

{

	return (struct mean_and_variance) {

		.n           = s.n + 1,

		.sum         = s.sum + v,

		.sum_squares = u128_add(s.sum_squares, u128_square(abs(v))),

	};

	s->n++;

	s->sum += v;

	s->sum_squares = u128_add(s->sum_squares, u128_square(abs(v)));

}



s64 mean_and_variance_get_mean(struct mean_and_variance s);

fs/bcachefs/mean_and_variance_test.c

+94 −7
Original line number Diff line number Diff line
@@ -9,15 +9,15 @@ static void mean_and_variance_basic_test(struct kunit *test) 
{

	struct mean_and_variance s = {};



	s = mean_and_variance_update(s, 2);

	s = mean_and_variance_update(s, 2);

	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);



	s = mean_and_variance_update(s, 4);

	s = mean_and_variance_update(s, 4);

	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);
@@ -33,8 +33,6 @@ static void mean_and_variance_weighted_test(struct kunit *test) 
{

	struct mean_and_variance_weighted s = { .weight = 2 };



	s.weight = 2;



	mean_and_variance_weighted_update(&s, 10);

	KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s), 10);

	KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s), 0);
@@ -60,7 +58,6 @@ static void mean_and_variance_weighted_test(struct kunit *test) 
	mean_and_variance_weighted_update(&s, -30);

	KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s), -16);

	KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s), 72);



}



static void mean_and_variance_weighted_advanced_test(struct kunit *test)
@@ -81,7 +78,93 @@ static void mean_and_variance_weighted_advanced_test(struct kunit *test) 


	KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_mean(s), -11);

	KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_variance(s), 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 = { .weight = weight };



	for (unsigned i = 0; i < initial_n; i++) {

		mean_and_variance_update(&mv, initial_value);

		mean_and_variance_weighted_update(&vw, initial_value);



		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),	initial_value);

		KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_stddev(vw),0);

	}



	for (unsigned i = 0; i < n; i++) {

		mean_and_variance_update(&mv, data[i]);

		mean_and_variance_weighted_update(&vw, data[i]);



		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),	weighted_mean[i]);

		KUNIT_EXPECT_EQ(test, mean_and_variance_weighted_get_stddev(vw),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)
@@ -139,6 +222,10 @@ static struct kunit_case mean_and_variance_test_cases[] = { 
	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),

	{}

};

fs/bcachefs/util.c

+2 −2
Original line number Diff line number Diff line
@@ -350,7 +350,7 @@ static inline void bch2_time_stats_update_one(struct bch2_time_stats *stats, 


	if (time_after64(end, start)) {

		duration = end - start;

		stats->duration_stats = mean_and_variance_update(stats->duration_stats, duration);

		mean_and_variance_update(&stats->duration_stats, duration);

		mean_and_variance_weighted_update(&stats->duration_stats_weighted, duration);

		stats->max_duration = max(stats->max_duration, duration);

		stats->min_duration = min(stats->min_duration, duration);
@@ -359,7 +359,7 @@ static inline void bch2_time_stats_update_one(struct bch2_time_stats *stats, 


	if (time_after64(end, stats->last_event)) {

		freq = end - stats->last_event;

		stats->freq_stats = mean_and_variance_update(stats->freq_stats, freq);

		mean_and_variance_update(&stats->freq_stats, freq);

		mean_and_variance_weighted_update(&stats->freq_stats_weighted, freq);

		stats->max_freq = max(stats->max_freq, freq);

		stats->min_freq = min(stats->min_freq, freq);