mathjs
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Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser and offers an integrated solution to work with numbers, big numbers, complex numbers, units, and matrices.
54 lines (44 loc) • 1.51 kB
HTML
<html>
<head>
<title>Pi Bailey-Borwein-Plouffe</title>
<script src="../node_modules/decimal.js/decimal.js"></script>
</head>
<body>
<script>
Decimal.config({precision: 100});
function pi() {
// the Bailey-Borwein-Plouffe formula
// http://stackoverflow.com/questions/4484489/using-basic-arithmetics-for-calculating-pi-with-arbitary-precision
var zero = new Decimal(0);
var one = new Decimal(1);
var two = new Decimal(2);
var four = new Decimal(4);
var p16 = one;
var pi = zero;
var precision = Decimal.config().precision;
var k8 = zero;
for (var k = zero; k.lte(precision); k = k.plus(one)) {
// pi += 1/p16 * (4/(8*k + 1) - 2/(8*k + 4) - 1/(8*k + 5) - 1/(8*k+6));
// p16 *= 16;
//
// a little simpler:
// pi += p16 * (4/(8*k + 1) - 2/(8*k + 4) - 1/(8*k + 5) - 1/(8*k+6));
// p16 /= 16;
var f = four.div(k8.plus(1))
.minus(two.div(k8.plus(4)))
.minus(one.div(k8.plus(5)))
.minus(one.div(k8.plus(6)));
pi = pi.plus(p16.times(f));
p16 = p16.div(16);
k8 = k8.plus(8);
}
return pi;
}
console.time('estimation');
var calculatedPi = pi();
console.timeEnd('estimation');
document.write('<code>Real: 3.14159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664...</code><br>');
document.write('<code>Est: ' + calculatedPi.toString() + '</code>');
</script>
</body>
</html>