2020-01-05 release

2025-11-17 03:01:51 +03:00 · 2020-09-06 18:53:08 +02:00
parent 9096e544ba
commit 91459fb672
63 changed files with 95633 additions and 0 deletions
--- a/examples/pi_bigdecimal.js
+++ b/examples/pi_bigdecimal.js
@@ -0,0 +1,70 @@
+/*
+ * 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 = 13591409d;
+    const CHUD_B = 545140134d;
+    const CHUD_C = 640320d;
+    const CHUD_C3 = 10939058860032000d; /* 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 = (2d * b1 - 1d) * (6d * b1 - 1d) * (6d * b1 - 5d);
+            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 = 0d;
+        }
+        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 / 12d) * 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);
+    r = BigDecimal.round(r, { roundingMode: "down",
+                              maximumFractionDigits: n_digits })
+    print(r);
+})();