Merge tag 'debian/1.52.1+dfsg1-1_exp2' into proxmox/buster

[rustc.git] / vendor / rand-0.7.3 / src / distributions / unit_circle.rs

diff --git a/vendor/rand-0.7.3/src/distributions/unit_circle.rs b/vendor/rand-0.7.3/src/distributions/unit_circle.rs
new file mode 100644 (file)
index 0000000..37885d8
--- /dev/null
+++ b/vendor/rand-0.7.3/src/distributions/unit_circle.rs
@@ -0,0 +1,102 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(deprecated)]
+#![allow(clippy::all)]
+
+use crate::distributions::{Distribution, Uniform};
+use crate::Rng;
+
+/// Samples uniformly from the edge of the unit circle in two dimensions.
+///
+/// Implemented via a method by von Neumann[^1].
+///
+/// [^1]: von Neumann, J. (1951) [*Various Techniques Used in Connection with
+///       Random Digits.*](https://mcnp.lanl.gov/pdf_files/nbs_vonneumann.pdf)
+///       NBS Appl. Math. Ser., No. 12. Washington, DC: U.S. Government Printing
+///       Office, pp. 36-38.
+#[deprecated(since = "0.7.0", note = "moved to rand_distr crate")]
+#[derive(Clone, Copy, Debug)]
+pub struct UnitCircle;
+
+impl UnitCircle {
+    /// Construct a new `UnitCircle` distribution.
+    #[inline]
+    pub fn new() -> UnitCircle {
+        UnitCircle
+    }
+}
+
+impl Distribution<[f64; 2]> for UnitCircle {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> [f64; 2] {
+        let uniform = Uniform::new(-1., 1.);
+        let mut x1;
+        let mut x2;
+        let mut sum;
+        loop {
+            x1 = uniform.sample(rng);
+            x2 = uniform.sample(rng);
+            sum = x1 * x1 + x2 * x2;
+            if sum < 1. {
+                break;
+            }
+        }
+        let diff = x1 * x1 - x2 * x2;
+        [diff / sum, 2. * x1 * x2 / sum]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::UnitCircle;
+    use crate::distributions::Distribution;
+
+    /// Assert that two numbers are almost equal to each other.
+    ///
+    /// On panic, this macro will print the values of the expressions with their
+    /// debug representations.
+    macro_rules! assert_almost_eq {
+        ($a:expr, $b:expr, $prec:expr) => {
+            let diff = ($a - $b).abs();
+            if diff > $prec {
+                panic!(format!(
+                    "assertion failed: `abs(left - right) = {:.1e} < {:e}`, \
+                     (left: `{}`, right: `{}`)",
+                    diff, $prec, $a, $b
+                ));
+            }
+        };
+    }
+
+    #[test]
+    fn norm() {
+        let mut rng = crate::test::rng(1);
+        let dist = UnitCircle::new();
+        for _ in 0..1000 {
+            let x = dist.sample(&mut rng);
+            assert_almost_eq!(x[0] * x[0] + x[1] * x[1], 1., 1e-15);
+        }
+    }
+
+    #[test]
+    fn value_stability() {
+        let mut rng = crate::test::rng(2);
+        let expected = [
+            [-0.9965658683520504, -0.08280380447614634],
+            [-0.9790853270389644, -0.20345004884984505],
+            [-0.8449189758898707, 0.5348943112253227],
+        ];
+        let samples = [
+            UnitCircle.sample(&mut rng),
+            UnitCircle.sample(&mut rng),
+            UnitCircle.sample(&mut rng),
+        ];
+        assert_eq!(samples, expected);
+    }
+}