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// Copyright 2018 Stefan Kroboth
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.
//! # Cross-in-tray test function
//!
//! Defined as
//!
//! `f(x_1, x_2) = -0.0001 * ( | sin(x_1)*sin(x_2)*exp(| 100 -
//! \sqrt{x_1^2+_2^2) / pi |) | + 1)^0.1`
//!
//! where `x_i \in [-10, 10]`.
//!
//! The global minima are at
//! * `f(x_1, x_2) = f(1.34941, 1.34941) = -2.06261`.
//! * `f(x_1, x_2) = f(1.34941, -1.34941) = -2.06261`.
//! * `f(x_1, x_2) = f(-1.34941, 1.34941) = -2.06261`.
//! * `f(x_1, x_2) = f(-1.34941, -1.34941) = -2.06261`.
use std::f64::consts::PI;
/// Cross-in-tray test function
///
/// Defined as
///
/// `f(x_1, x_2) = -0.0001 * ( | sin(x_1)*sin(x_2)*exp(| 100 -
/// \sqrt{x_1^2+_2^2) / pi |) | + 1)^0.1`
///
/// where `x_i \in [-10, 10]`.
///
/// The global minima are at
/// * `f(x_1, x_2) = f(1.34941, 1.34941) = -2.06261`.
/// * `f(x_1, x_2) = f(1.34941, -1.34941) = -2.06261`.
/// * `f(x_1, x_2) = f(-1.34941, 1.34941) = -2.06261`.
/// * `f(x_1, x_2) = f(-1.34941, -1.34941) = -2.06261`.
pub fn cross_in_tray(param: &[f64]) -> f64 {
assert!(param.len() == 2);
let (x1, x2) = (param[0], param[1]);
// let pi = T::from_f64(PI).unwrap();
// T::from_f64(-0.0001).unwrap()
// * ((x1.sin() * x2.sin()
// * (T::from_f64(100.0).unwrap() - (x1.powi(2) + x2.powi(2)).sqrt() / pi)
// .abs()
// .exp())
// .abs() + T::from_f64(1.0).unwrap())
// .powf(T::from_f64(0.1).unwrap())
-0.0001
* ((x1.sin() * x2.sin() * (100.0 - (x1.powi(2) + x2.powi(2)).sqrt() / PI).abs().exp()).abs()
+ 1.0)
.powf(0.1)
}
mod tests {
#[test]
fn test_cross_in_tray_optimum() {
// This isnt exactly a great way to test this. The function can only be computed with the
// use of f64; however, I only have the minimum points available in f32, which is why I use
// the f32 EPSILONs.
assert!(
(::cross_in_tray(&[1.34941_f64, 1.34941_f64]) + 2.062611870).abs()
< ::std::f32::EPSILON.into()
);
assert!(
(::cross_in_tray(&[1.34941_f64, -1.34941_f64]) + 2.062611870).abs()
< ::std::f32::EPSILON.into()
);
assert!(
(::cross_in_tray(&[-1.34941_f64, 1.34941_f64]) + 2.062611870).abs()
< ::std::f32::EPSILON.into()
);
assert!(
(::cross_in_tray(&[-1.34941_f64, -1.34941_f64]) + 2.062611870).abs()
< ::std::f32::EPSILON.into()
);
}
#[test]
#[should_panic]
fn test_cross_in_tray_param_length() {
::cross_in_tray(&[0.0, -1.0, 0.1]);
}
}