siderust 0.7.0

High-precision astronomy and satellite mechanics in Rust.
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
151
152
153
154
155
156

// SPDX-License-Identifier: AGPL-3.0-or-later
// Copyright (C) 2026 Vallés Puig, Ramon

//! Integration tests for `math_core::root_finding`, the astronomy-agnostic
//! Brent & bisection solvers that use typed [`qtty`] quantities.

use siderust::calculus::math_core::root_finding;
use siderust::qtty::{Day, Quantity, Radian};
use siderust::time::{ModifiedJulianDate, Period};
use std::cell::Cell;

type Days = Quantity<Day>;
type Mjd = ModifiedJulianDate;
type Radians = Quantity<Radian>;

// =============================================================================
// Brent's method
// =============================================================================

#[test]
fn brent_finds_sine_root_near_pi() {
    let root = root_finding::brent(Days::new(3.0), Days::new(4.0), |t: Days| {
        Radians::new(t.value().sin())
    })
    .expect("should find π");
    assert!(
        (root.value() - std::f64::consts::PI).abs() < 1e-9,
        "expected root near π, got {}",
        root.value()
    );
}

#[test]
fn brent_finds_linear_root() {
    let root = root_finding::brent(Days::new(0.0), Days::new(10.0), |t: Days| {
        Radians::new(t.value() - 5.0)
    })
    .expect("should find 5");
    assert!((root.value() - 5.0).abs() < 1e-10);
}

#[test]
fn brent_handles_step_function() {
    let root = root_finding::brent(Days::new(-2.0), Days::new(2.0), |t: Days| {
        Radians::new(if t.value() < 0.0 { -5.0 } else { 5.0 })
    })
    .expect("step crossing");
    assert!(root.abs().value() < 1e-6);
}

#[test]
fn brent_returns_none_for_invalid_bracket() {
    assert!(
        root_finding::brent(Days::new(0.0), Days::new(1.0), |_: Days| Radians::new(42.0)).is_none()
    );
}

#[test]
fn brent_returns_endpoint_when_exact() {
    let root = root_finding::brent(Days::new(0.0), Days::new(5.0), |t: Days| {
        Radians::new(t.value() - 5.0)
    })
    .expect("endpoint root");
    assert!((root.value() - 5.0).abs() < 1e-12);
}

#[test]
fn brent_with_values_saves_evaluations() {
    let count = Cell::new(0usize);
    let f = |t: Mjd| -> Radians {
        count.set(count.get() + 1);
        Radians::new(t.mjd_value().sin())
    };
    let f_lo = Radians::new((3.0_f64).sin());
    let f_hi = Radians::new((4.0_f64).sin());

    let _ =
        root_finding::brent_with_values(Period::new(Mjd::new(3.0), Mjd::new(4.0)), f_lo, f_hi, f);
    let with_vals = count.get();

    count.set(0);
    let _ = root_finding::brent(Days::new(3.0), Days::new(4.0), |t: Days| {
        count.set(count.get() + 1);
        Radians::new(t.value().sin())
    });
    let without = count.get();

    // brent_with_values saves the 2 endpoint evaluations
    assert!(
        with_vals <= without,
        "with_values used {} calls, plain brent used {}",
        with_vals,
        without
    );
}

#[test]
fn brent_tol_respects_relaxed_tolerance() {
    let root = root_finding::brent_tol(
        Period::new(Mjd::new(3.0), Mjd::new(4.0)),
        Radians::new((3.0_f64).sin()),
        Radians::new((4.0_f64).sin()),
        |t: Mjd| Radians::new(t.mjd_value().sin()),
        Days::new(1e-3),
    )
    .expect("relaxed tolerance");
    assert!((root.mjd_value() - std::f64::consts::PI).abs() < 2e-3);
}

#[test]
fn brent_cubic() {
    let root = root_finding::brent(Days::new(1.0), Days::new(2.0), |t: Days| {
        Radians::new(t.value().powi(3) - 2.0)
    })
    .expect("cbrt 2");
    assert!((root.value() - 2.0_f64.powf(1.0 / 3.0)).abs() < 1e-9);
}

// =============================================================================
// Bisection
// =============================================================================

#[test]
fn bisection_finds_sine_root() {
    let root = root_finding::bisection(Days::new(3.0), Days::new(4.0), |t: Days| {
        Radians::new(t.value().sin())
    })
    .expect("π via bisection");
    assert!((root.value() - std::f64::consts::PI).abs() < 1e-8);
}

#[test]
fn bisection_returns_none_for_invalid_bracket() {
    assert!(
        root_finding::bisection(Days::new(0.0), Days::new(1.0), |_: Days| Radians::new(42.0))
            .is_none()
    );
}

#[test]
fn bisection_handles_step_function() {
    let root = root_finding::bisection(Days::new(-1.0), Days::new(1.0), |t: Days| {
        Radians::new(if t.value() < 0.0 { -5.0 } else { 5.0 })
    })
    .expect("step crossing via bisection");
    assert!(root.abs().value() < 1e-6);
}

#[test]
fn bisection_endpoint_root() {
    let root = root_finding::bisection(Days::new(0.0), Days::new(5.0), |t: Days| {
        Radians::new(t.value())
    })
    .expect("root at 0");
    assert!(root.abs().value() < 1e-12);
}