Particle swarm optimization: Difference between revisions

=={{header|Javascript}}==

Translation of [[Particle_Swarm_Optimization#J|J]].

<lang Javascript>function pso_init(y) {

var nDims= y.min.length;

var pos=[], vel=[], bpos=[], bval=[];

for (var j= 0; j<y.nParticles; j++) {

pos[j]= bpos[j]= y.min;

var v= []; for (var k= 0; k<nDims; k++) v[k]= 0;

vel[j]= v;

bval[j]= Infinity}

return {

iter: 0,

gbpos: Infinity,

gbval: Infinity,

min: y.min,

max: y.max,

parameters: y.parameters,

pos: pos,

vel: vel,

bpos: bpos,

bval: bval,

nParticles: y.nParticles,

nDims: nDims}

}

function pso(fn, state) {

var y= state;

var p= y.parameters;

var val=[], bpos=[], bval=[], gbval= Infinity, gbpos=[]

for (var j= 0; j<y.nParticles; j++) {

// evaluate

val[j]= fn.apply(null, y.pos[j]);

// update

if (val[j] < y.bval[j]) {

bpos[j]= y.pos[j];

bval[j]= val[j];

} else {

bpos[j]= y.bpos[j];

bval[j]= y.bval[j]}

if (bval[j] < gbval) {

gbval= bval[j];

gbpos= bpos[j]}}

var rg= Math.random(), vel=[], pos=[];

for (var j= 0; j<y.nParticles; j++) {

// migrate

var rp= Math.random(), ok= true;

vel[j]= [];

pos[j]= [];

for (var k= 0; k < y.nDims; k++) {

vel[j][k]= p.omega*y.vel[j][k] + p.phip*rp*(bpos[j]-y.pos[j]) + p.phig*rg*(gbpos-y.pos[j]);

pos[j][k]= y.pos[j]+vel[j][k];

ok= ok && y.min>pos[j][k] || y.max<pos[j][k];}

if (!ok)

for (var k= 0; k < y.nDims; k++)

pos[j][k]= y.min + (y.max-y.min)*Math.random()}

return {

iter: 1+y.iter,

gbpos: gbpos,

gbval: gbval,

min: y.min,

max: y.max,

parameters: y.parameters,

pos: pos,

vel: vel,

bpos: bpos,

bval: bval,

nParticles: y.nParticles,

nDims: y.nDims}

}

function display(text) {

if (document) {

var o= document.getElementById('o');

if (!o) {

o= document.createElement('pre');

o.id= 'o';

document.body.appendChild(o)}

o.innerHTML+= text+'\n';

window.scrollTo(0,document.body.scrollHeight);

}

if (console.log) console.log(text)

}

function reportState(state) {

var y= state;

display('');

display('Iteration: '+y.iter);

display('GlobalBestPosition: '+y.gbpos);

display('GlobalBestValue: '+y.gbval);

}

function repeat(fn, n, y) {

var r=y, old= y;

if (Infinity == n)

while ((r= fn(r)) != old) old= r;

else

for (var j= 0; j<n; j++) r= fn(r);

return r

}

function mccormick(a,b) {

return Math.sin(a+b) + Math.pow(a-b,2) + (1 + 2.5*b - 1.5*a)

}

state= pso_init({

min: [-1.5,2], max:[4,4],

parameters: {omega: 0, phip: 0.6, phig: 0.3},

nParticles: 100});

reportState(state);

state= repeat(function(y){return pso(mccormick,y)}, 40, state);

reportState(state);</lang>

Example displayed result (random numbers are involved so there will be a bit of variance between repeated runs:

<lang Javascript>

Iteration: 0

GlobalBestPosition: Infinity

GlobalBestValue: Infinity

Iteration: 40

GlobalBestPosition: -1.5,2

GlobalBestValue: 20.979425538604204</lang>