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
// 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. //! # Styblinski-Tang test function //! //! Defined as //! //! `f(x_1, x_2, ..., x_n) = 1/2 * \sum_{i=1}^{n} \left[ x_i^4 - 16 * x_i^2 + 5 * x_i \right]` //! //! where `x_i \in [-5, 5]`. //! //! The global minimum is at `f(x_1, x_2, ..., x_n) = f(-2.903534, -2.903534, ..., -2.903534) = //! -39.16616*n`. use num::{Float, FromPrimitive}; use std::iter::Sum; /// Styblinski-Tang test function /// /// Defined as /// /// `f(x_1, x_2, ..., x_n) = 1/2 * \sum_{i=1}^{n} \left[ x_i^4 - 16 * x_i^2 + 5 * x_i \right]` /// /// where `x_i \in [-5, 5]`. /// /// The global minimum is at `f(x_1, x_2, ..., x_n) = f(-2.903534, -2.903534, ..., -2.903534) = /// -39.16616*n`. pub fn styblinski_tang<T: Float + FromPrimitive + Sum>(param: &[T]) -> T { T::from_f64(0.5).unwrap() * param .iter() .map(|x| { x.powi(4) - T::from_f64(16.0).unwrap() * x.powi(2) + T::from_f64(5.0).unwrap() * *x }) .sum() } mod tests { #[test] fn test_styblinski_tang_optimum() { assert!( (::styblinski_tang(&[-2.903534_f32, -2.903534_f32, -2.903534_f32]) + 117.49849_f32) .abs() < ::std::f32::EPSILON ); } }