ic-metrics 0.8.0

Allocation-free, dependency-free measurement arithmetic
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150

use crate::MeasurementAggregate;

use super::{MeasurementMeanError, MeasurementSummary};

#[test]
fn summary_mean_preserves_recording_and_saturation_contracts() {
    let mut summary = MeasurementSummary::EMPTY;
    assert_eq!(summary.mean(), Ok(None));
    summary.record(0);
    assert_eq!(summary.mean(), Ok(Some(0)));
    summary.record(9);
    assert_eq!(summary.mean(), Ok(Some(4)));
    summary.record(u64::MAX - 9);
    assert_eq!(summary.total(), u128::from(u64::MAX));
    assert_eq!(summary.mean(), Ok(Some(u128::from(u64::MAX) / 3)));
    assert!(!summary.aggregate().total_saturated());
    summary.record(1);
    assert_eq!(summary.mean(), Ok(Some((u128::from(u64::MAX) + 1) / 4)));
    assert!(!summary.aggregate().total_saturated());
    assert_eq!(summary.latest(), Some(1));
    let mut saturated_count = MeasurementSummary {
        aggregate: maximum_zero_count(),
        latest: 0,
    };
    assert_eq!(saturated_count.mean(), Ok(Some(0)));
    saturated_count.record(9);
    assert_eq!(
        saturated_count.mean(),
        Err(MeasurementMeanError::SaturatedSamples)
    );
}

#[test]
fn summary_means_are_available_in_constant_evaluation() {
    const PROJECTIONS: (Option<u128>, Option<u128>) = {
        let mut summary = MeasurementSummary::EMPTY;
        summary.record(9);
        summary.record(0);
        let Ok(mean) = summary.mean() else {
            panic!("exact mean")
        };
        let Ok(scaled) = summary.scaled_mean(10) else {
            panic!("exact scaled mean")
        };
        (mean, scaled)
    };
    assert_eq!(PROJECTIONS, (Some(4), Some(45)));
    let mut summary = MeasurementSummary::EMPTY;
    assert_eq!(summary.scaled_mean(10), Ok(None));
    summary.record(0);
    assert_eq!(summary.scaled_mean(10), Ok(Some(0)));
    summary = MeasurementSummary::from_parts(maximum_zero_count(), Some(0)).unwrap();
    assert_eq!(summary.scaled_mean(u64::MAX), Ok(Some(0)));
    summary.record(0);
    assert_eq!(
        summary.scaled_mean(0),
        Err(MeasurementMeanError::SaturatedSamples)
    );
}

#[test]
fn empty_and_measured_zero_are_distinct() {
    let mut summary = MeasurementSummary::EMPTY;
    assert_eq!(summary, MeasurementSummary::default());
    assert_eq!(summary.samples(), 0);
    assert_eq!(summary.total(), 0);
    assert_eq!(summary.latest(), None);
    assert_eq!(summary.maximum(), None);

    summary.record(0);
    assert_eq!(summary.samples(), 1);
    assert_eq!(summary.total(), 0);
    assert_eq!(summary.latest(), Some(0));
    assert_eq!(summary.maximum(), Some(0));
}

#[test]
fn latest_and_maximum_follow_individual_observations() {
    let mut summary = MeasurementSummary::EMPTY;
    for value in [7, 12, 3, 0] {
        summary.record(value);
    }
    assert_eq!(summary.samples(), 4);
    assert_eq!(summary.total(), 22);
    assert_eq!(summary.latest(), Some(0));
    assert_eq!(summary.maximum(), Some(12));
}

#[test]
fn total_saturation_preserves_count_latest_and_maximum() {
    let mut aggregate = MeasurementAggregate::EMPTY;
    for _ in 0..64 {
        aggregate.merge(aggregate);
        aggregate.record(u64::MAX);
    }
    aggregate.record(u64::MAX);
    aggregate.record(u64::MAX);
    let mut summary = MeasurementSummary {
        aggregate,
        latest: u64::MAX,
    };
    assert_eq!(summary.total(), u128::MAX);
    assert!(!summary.aggregate().total_saturated());
    summary.record(1);
    summary.record(2);
    assert_eq!(summary.samples(), u64::MAX);
    assert_eq!(summary.total(), u128::MAX);
    assert!(summary.aggregate().samples_saturated());
    assert!(summary.aggregate().total_saturated());
    assert_eq!(summary.latest(), Some(2));
    assert_eq!(summary.maximum(), Some(u64::MAX));
}

#[test]
fn count_saturation_does_not_freeze_other_observations() {
    let mut summary = MeasurementSummary {
        aggregate: maximum_zero_count(),
        latest: 0,
    };
    summary.record(4);
    assert_eq!(summary.samples(), u64::MAX);
    assert_eq!(summary.total(), 4);
    assert_eq!(summary.latest(), Some(4));
    assert_eq!(summary.maximum(), Some(4));
}

#[test]
fn recording_is_available_in_constant_evaluation() {
    const SUMMARY: MeasurementSummary = {
        let mut summary = MeasurementSummary::EMPTY;
        summary.record(9);
        summary.record(2);
        summary
    };
    assert_eq!(SUMMARY.samples(), 2);
    assert_eq!(SUMMARY.total(), 11);
    assert_eq!(SUMMARY.latest(), Some(2));
    assert_eq!(SUMMARY.maximum(), Some(9));
}

// Repeated disjoint zero-sample batches construct an exact cap without a fake
// production path or an impractically large recording loop.
fn maximum_zero_count() -> MeasurementAggregate {
    let mut aggregate = MeasurementAggregate::EMPTY;
    for _ in 0..64 {
        aggregate.merge(aggregate);
        aggregate.record(0);
    }
    aggregate
}