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fix newtons_method handling of non-finite derivatives

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This commit is contained in:
Simon Gardling 2022-05-18 15:01:33 -04:00
parent d665b72a4c
commit 782d567302
2 changed files with 25 additions and 1 deletions
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8
src/misc.rs
View File

@ -253,8 +253,14 @@ pub fn newtons_method(
) -> Option<f64> { ) -> Option<f64> {
let mut x1: f64 = *start_x; let mut x1: f64 = *start_x;
let mut x2: f64; let mut x2: f64;
let mut derivative: f64;
loop { loop {
x2 = x1 - (f(x1) / f_1(x1)); derivative = f_1(x1);
if !derivative.is_finite() {
return None;
}
x2 = x1 - (f(x1) / derivative);
if !x2.is_finite() | !range.contains(&x2) { if !x2.is_finite() | !range.contains(&x2) {
return None; return None;
} }

18
tests/misc.rs
View File

@ -201,4 +201,22 @@ fn newtons_method() {
&f64::EPSILON, &f64::EPSILON,
); );
assert_eq!(data, None); assert_eq!(data, None);
let data = newtons_method(
&|_: f64| f64::INFINITY,
&|x: f64| x.sin(),
&0.0,
&(-10.0..10.0),
&f64::EPSILON,
);
assert_eq!(data, None);
let data = newtons_method(
&|x: f64| x.sin(),
&|_: f64| f64::INFINITY,
&0.0,
&(-10.0..10.0),
&f64::EPSILON,
);
assert_eq!(data, None);
} }