e2rcore/implement/math/
sim_anneal.rs

1extern crate rand;
2
3use std::f32;
4use self::rand::distributions::{IndependentSample, Range};
5
6pub fn compute_discrete< F0, F1, F2 >( domain: &[ f32 ], candidate_generator: F0, temperature_function: F1, energy_function: F2, max_iter: usize, initial: usize ) -> usize
7    where F0: Fn( &[ f32 ], usize ) -> ( usize ), F1: Fn( f32 ) -> f32, F2: Fn( &[ f32 ], usize )-> f32
8
9{
10    assert!( initial < domain.len() );
11
12    let between = Range::new(0f32, 1f32);
13    let mut rng = rand::thread_rng();
14
15    let mut state = initial; //state is the index within the domain slice
16
17    for i in 0..max_iter {
18        // println!( "state: {:?}", state );
19        let k = i as f32/ max_iter as f32;
20        let t = temperature_function( k ); //output range between [0,1]
21        let candidate = candidate_generator( &domain[..], i ); //candidate is the index within the domain slice
22        let r = between.ind_sample(&mut rng); //generate from a uniform distribution [0,1]
23        let e_current = energy_function( &domain[..], state );
24        let e_candidate = energy_function( &domain[..], candidate );
25        let e_diff = e_candidate - e_current; // diff is between [-1, 1]
26        if e_diff < 0f32 { //candidate energy is lower than current
27            state = candidate;
28        } else { //diff is between [0, 1]
29            let a = t * e_diff;
30            if a > r {
31                state = candidate;                
32            }
33        }
34    }
35    state
36}
37
38pub fn temperature_function_default( fraction: f32 ) -> f32 {
39    assert!( fraction >= 0f32 && fraction <= 1f32 );
40    f32::consts::E.powf( -fraction * 7f32 )
41}
42
43pub fn candidate_generator_default( input: &[f32], _index_current: usize ) -> usize {
44    let between = Range::new(0usize, input.len() );
45    let mut rng = rand::thread_rng();
46    between.ind_sample(&mut rng)
47}
48
49pub fn energy_function_default( input: &[f32], index_current: usize ) -> f32 {
50    let e = input[index_current];
51    assert!( e >= 0f32 );
52    assert!( e <= 1f32 );
53    e
54}
e2rcore/implement/math/sim_anneal.rs

e2rcore/implement/math/
sim_anneal.rs
