使用 JavaScript 编写优化算法 (1)

#!/usr/bin/env node --harmony

// Random Search

"use strict";

var util = require("util");

function objective_function(v) {
    return v.map(function(x) {
        return x*x;
    }).reduce(function(a, b) {
        return a+b;
    });
}

function random_vector(min_max) {
    return min_max.map(function(x) {
        return x[0] + (x[1] - x[0]) * Math.random();
    });
}

function search(search_space, max_iteration) {
    var best = {};
    for (var iteration = 0; iteration < max_iteration; iteration++) {
        var candidate = {
            ‘vector‘: random_vector(search_space)
        };
        candidate[‘cost‘] = objective_function(candidate[‘vector‘]);
        //console.log(candidate);
        if (iteration === 0 || candidate[‘cost‘] < best[‘cost‘]) {
            best = candidate;
        }
        console.log(‘ > iteration=‘ + (iteration+1) + ‘, best=‘ + best[‘cost‘]);
    }
    return best;
}

function generate_array(element, repeat) {
    return new Array(repeat+1).join(1).split(‘‘).map(function(){return element;});
}

function run () {
    var problem_size = 2;
    var search_space = generate_array([-5, 5], problem_size);
    var max_iteration = 100;
    var best = search(search_space, max_iteration);
    console.log("Done. Best Solution: " + util.inspect(best));
}

exports.objective_function = objective_function;
exports.random_vector = random_vector;
exports.generate_array = generate_array;
exports.search = search;
exports.run = run;

var rs = require(‘clever_algorithms_js‘).random_search;

rs.run();

var random_search = require(‘../../lib/stochastic/random_search‘);

exports[‘objective‘] = function (test) {
    test.equal(random_search.objective_function([1, 2]), 5);
    test.done();
};

exports[‘random_vector‘] = function (test) {
    var rv = random_search.random_vector([[1, 2], [2, 3]]);
    test.equal(rv.length, 2);
    test.ok(1 <= rv[0] && rv[0] <= 2);
    test.ok(2 <= rv[1] && rv[1] <= 3);
    test.done();
};

exports[‘generate_array‘] = function (test) {
    var a = random_search.generate_array([-5, 5], 2);
    test.equal(a.length, 2);
    test.deepEqual(a, [[-5,5], [-5,5]]);
    test.done();
};

exports[‘search‘] = function (test) {
    var problem_size = 2,
        search_space = random_search.generate_array([-5, 5], problem_size),
        max_iter = 100;
    var best = random_search.search(search_space, max_iter);
    test.notEqual(best, {});
    test.ok(-5 <= best[‘cost‘] && best[‘cost‘] <= 5);
    test.done();
};