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/**
* Created by joonkukang on 2014. 1. 16..
*/
var math = require('./utils').math;
let optimize = module.exports;
optimize.hillclimb = function(options){
var domain = options['domain'];
var costf = options['costf'];
var i;
var vec = [];
for(i=0 ; i<domain.length ; i++)
vec.push(math.randInt(domain[i][0],domain[i][1]));
var current, best;
while(true) {
var neighbors = [];
var i,j;
for(i=0 ; i<domain.length ; i++) {
if(vec[i] > domain[i][0]) {
var newVec = [];
for(j=0 ; j<domain.length ; j++)
newVec.push(vec[j]);
newVec[i]-=1;
neighbors.push(newVec);
} else if (vec[i] < domain[i][1]) {
var newVec = [];
for(j=0 ; j<domain.length ; j++)
newVec.push(vec[j]);
newVec[i]+=1;
neighbors.push(newVec);
}
}
current = costf(vec);
best = current;
for(i=0 ; i<neighbors.length ; i++) {
var cost = costf(neighbors[i]);
if(cost < best) {
best = cost;
vec = neighbors[i];
}
}
if(best === current)
break;
}
return vec;
}
optimize.anneal = function(options){
var domain = options['domain'];
var costf = options['costf'];
var temperature = options['temperature'];
var cool = options['cool'];
var step = options['step'];
var callback
var i;
var vec = [];
for(i=0 ; i<domain.length ; i++)
vec.push(math.randInt(domain[i][0],domain[i][1]));
while(temperature > 0.1) {
var idx = math.randInt(0,domain.length - 1);
var dir = math.randInt(-step,step);
var newVec = [];
for(i=0; i<vec.length ; i++)
newVec.push(vec[i]);
newVec[idx]+=dir;
if(newVec[idx] < domain[idx][0]) newVec[idx] = domain[idx][0];
if(newVec[idx] > domain[idx][1]) newVec[idx] = domain[idx][1];
var ea = costf(vec);
var eb = costf(newVec);
var p = Math.exp(-1.*(eb-ea)/temperature);
if(eb < ea || Math.random() < p)
vec = newVec;
temperature *= cool;
}
return vec;
}
optimize.genetic = function(options){
var domain = options['domain'];
var costf = options['costf'];
var population = options['population'];
var q = options['q'] || 0.3;
var elite = options['elite'] || population * 0.04;
var epochs = options['epochs'] || 100;
var i,j;
// Initialize population array
var pop =[];
for(i=0; i<population; i++) {
var vec = [];
for(j=0; j<domain.length; j++)
vec.push(math.randInt(domain[j][0],domain[j][1]));
pop.push(vec);
}
pop.sort(function(a,b){return costf(a) - costf(b);});
for(i=0 ; i<epochs ; i++) {
// elitism
var newPop = [];
for(j=0;j<elite;j++)
newPop.push(pop[j]);
// compute fitnesses
var fitnesses = [];
for(j=0; j<pop.length; j++)
fitnesses[j] = q * Math.pow(1-q,j);
fitnesses = math.normalizeVec(fitnesses);
// crossover, mutate
for(j=0; j<pop.length - elite;j++) {
var idx1 = rouletteWheel(fitnesses);
var idx2 = rouletteWheel(fitnesses);
var crossovered = crossover(pop[idx1],pop[idx2]);
var mutated = mutate(crossovered);
newPop.push(mutated);
}
// replacement
pop = newPop;
pop.sort(function(a,b){return costf(a) - costf(b);});
//console.log("Current Cost : ",costf(pop[0]));
}
return pop[0];
function mutate(vec) {
var idx = math.randInt(0,domain.length - 1);
var newVec = [];
var i;
for(i=0; i<domain.length ; i++)
newVec.push(vec[i]);
newVec[idx] += (Math.random() < 0.5) ? 1 : -1;
if(newVec[idx] < domain[idx][0]) newVec[idx] = domain[idx][0];
if(newVec[idx] > domain[idx][1]) newVec[idx] = domain[idx][1];
return newVec;
}
function crossover(vec1,vec2) {
var idx = math.randInt(0,domain.length - 2);
var newVec = [];
var i;
for(i=0; i<idx ; i++)
newVec.push(vec1[i]);
for(i=idx; i<domain.length; i++)
newVec.push(vec2[i]);
return newVec;
}
function rouletteWheel(vec) {
var a = [0.0];
var i;
for(i=0;i<vec.length;i++) {
a.push(a[i] + vec[i]);
}
var rand = Math.random();
for(i=0;i< a.length;i++) {
if(rand > a[i] && rand <= a[i+1])
return i;
}
return -1;
}
};