Data update

Task/Arithmetic-geometric-mean-Calculate-Pi/JavaScript/arithmetic-geometric-mean-calculate-pi.js

@@ -0,0 +1,38 @@
+const Decimal = require('decimal.js');
+
+// Set global precision (e.g., 512 digits)
+Decimal.set({ precision: 512 });
+
+const bigTwo = new Decimal(2);
+const bigFour = new Decimal(4);
+
+function bigSqrt(bd) {
+    let x0 = new Decimal(0);
+    let x1 = new Decimal(Math.sqrt(bd.toNumber()));
+    while (!x0.equals(x1)) {
+        x0 = x1;
+        x1 = bd.div(x0).plus(x0).div(bigTwo);
+    }
+    return x1;
+}
+
+function calculatePi() {
+    let a = new Decimal(1);
+    let g = a.div(bigSqrt(bigTwo));
+    let t;
+    let sum = new Decimal(0);
+    let pow = bigTwo;
+
+    while (!a.equals(g)) {
+        t = a.plus(g).div(bigTwo);
+        g = bigSqrt(a.times(g));
+        a = t;
+        pow = pow.times(bigTwo);
+        sum = sum.plus(a.times(a).minus(g.times(g)).times(pow));
+    }
+
+    const pi = bigFour.times(a.times(a)).div(new Decimal(1).minus(sum));
+    console.log(pi.toString());
+}
+
+calculatePi();