Run results for: atan2 vs acos

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:120.0) Gecko/20100101 Firefox/120.0

Browser: Firefox 120

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
acos	2801.6 Ops/sec
atan2	81.8 Ops/sec

Script Preparation code:

var N = 1000000;
var x = new Float32Array(N);
var y = new Float32Array(N);

for (var i = 0; i < N; ++i) {
    x[i] = 100 * Math.random();
    y[i] = 100 * Math.random();
}

Tests:

acos
var fn = Math.acos; for (var i = 0; i < N; ++i) { fn(x[i]/Math.sqrt(x[i]*x[i]+y[i]*y[i])); }
atan2
var fn = Math.atan; for (var i = 0; i < N; ++i) { fn(y[i], x[i]); }