/* * PI computation in Javascript using the QuickJS bigdecimal type * (decimal floating point) */"use strict"; /* compute PI with a precision of 'prec' digits */function calc_pi(prec) { const CHUD_A = 13591409m; const CHUD_B = 545140134m; const CHUD_C = 640320m; const CHUD_C3 = 10939058860032000m; /* C^3/24 */ const CHUD_DIGITS_PER_TERM = 14.18164746272548; /* log10(C/12)*3 */ /* return [P, Q, G] */ function chud_bs(a, b, need_G) { var c, P, Q, G, P1, Q1, G1, P2, Q2, G2, b1; if (a == (b - 1n)) { b1 = BigDecimal(b); G = (2m * b1 - 1m) * (6m * b1 - 1m) * (6m * b1 - 5m); P = G * (CHUD_B * b1 + CHUD_A); if (b & 1n) P = -P; G = G; Q = b1 * b1 * b1 * CHUD_C3; } else { c = (a + b) >> 1n; [P1, Q1, G1] = chud_bs(a, c, true); [P2, Q2, G2] = chud_bs(c, b, need_G); P = P1 * Q2 + P2 * G1; Q = Q1 * Q2; if (need_G) G = G1 * G2; else G = 0m; } return [P, Q, G]; } var n, P, Q, G; /* number of serie terms */ n = BigInt(Math.ceil(prec / CHUD_DIGITS_PER_TERM)) + 10n; [P, Q, G] = chud_bs(0n, n, false); Q = BigDecimal.div(Q, (P + Q * CHUD_A), { roundingMode: "half-even", maximumSignificantDigits: prec }); G = (CHUD_C / 12m) * BigDecimal.sqrt(CHUD_C, { roundingMode: "half-even", maximumSignificantDigits: prec }); return Q * G;} (function() { var r, n_digits, n_bits; if (typeof scriptArgs != "undefined") { if (scriptArgs.length < 2) { print("usage: pi n_digits"); return; } n_digits = scriptArgs[1] | 0; } else { n_digits = 1000; } /* we add more digits to reduce the probability of bad rounding for the last digits */ r = calc_pi(n_digits + 20); print(r.toFixed(n_digits, "down"));})();
/*
* PI computation in Javascript using the QuickJS bigdecimal type
* (decimal floating point)
*/
"use strict";
/* compute PI with a precision of 'prec' digits */
function calc_pi(prec) {
const CHUD_A = 13591409m;
const CHUD_B = 545140134m;
const CHUD_C = 640320m;
const CHUD_C3 = 10939058860032000m; /* C^3/24 */
const CHUD_DIGITS_PER_TERM = 14.18164746272548; /* log10(C/12)*3 */
/* return [P, Q, G] */
function chud_bs(a, b, need_G) {
var c, P, Q, G, P1, Q1, G1, P2, Q2, G2, b1;
if (a == (b - 1n)) {
b1 = BigDecimal(b);
G = (2m * b1 - 1m) * (6m * b1 - 1m) * (6m * b1 - 5m);
P = G * (CHUD_B * b1 + CHUD_A);
if (b & 1n)
P = -P;
G = G;
Q = b1 * b1 * b1 * CHUD_C3;
} else {
c = (a + b) >> 1n;
[P1, Q1, G1] = chud_bs(a, c, true);
[P2, Q2, G2] = chud_bs(c, b, need_G);
P = P1 * Q2 + P2 * G1;
Q = Q1 * Q2;
if (need_G)
G = G1 * G2;
else
G = 0m;
}
return [P, Q, G];
}
var n, P, Q, G;
/* number of serie terms */
n = BigInt(Math.ceil(prec / CHUD_DIGITS_PER_TERM)) + 10n;
[P, Q, G] = chud_bs(0n, n, false);
Q = BigDecimal.div(Q, (P + Q * CHUD_A),
{ roundingMode: "half-even",
maximumSignificantDigits: prec });
G = (CHUD_C / 12m) * BigDecimal.sqrt(CHUD_C,
{ roundingMode: "half-even",
maximumSignificantDigits: prec });
return Q * G;
}
(function() {
var r, n_digits, n_bits;
if (typeof scriptArgs != "undefined") {
if (scriptArgs.length < 2) {
print("usage: pi n_digits");
return;
}
n_digits = scriptArgs[1] | 0;
} else {
n_digits = 1000;
}
/* we add more digits to reduce the probability of bad rounding for
the last digits */
r = calc_pi(n_digits + 20);
print(r.toFixed(n_digits, "down"));
})();