Data commit

Task/Arithmetic-geometric-mean-Calculate-Pi/Java/arithmetic-geometric-mean-calculate-pi.java

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+import java.math.BigDecimal;
+import java.math.MathContext;
+import java.util.Objects;
+
+public class Calculate_Pi {
+    private static final MathContext con1024 = new MathContext(1024);
+    private static final BigDecimal bigTwo = new BigDecimal(2);
+    private static final BigDecimal bigFour = new BigDecimal(4);
+
+    private static BigDecimal bigSqrt(BigDecimal bd, MathContext con) {
+        BigDecimal x0 = BigDecimal.ZERO;
+        BigDecimal x1 = BigDecimal.valueOf(Math.sqrt(bd.doubleValue()));
+        while (!Objects.equals(x0, x1)) {
+            x0 = x1;
+            x1 = bd.divide(x0, con).add(x0).divide(bigTwo, con);
+        }
+        return x1;
+    }
+
+    public static void main(String[] args) {
+        BigDecimal a = BigDecimal.ONE;
+        BigDecimal g = a.divide(bigSqrt(bigTwo, con1024), con1024);
+        BigDecimal t;
+        BigDecimal sum = BigDecimal.ZERO;
+        BigDecimal pow = bigTwo;
+        while (!Objects.equals(a, g)) {
+            t = a.add(g).divide(bigTwo, con1024);
+            g = bigSqrt(a.multiply(g), con1024);
+            a = t;
+            pow = pow.multiply(bigTwo);
+            sum = sum.add(a.multiply(a).subtract(g.multiply(g)).multiply(pow));
+        }
+        BigDecimal pi = bigFour.multiply(a.multiply(a)).divide(BigDecimal.ONE.subtract(sum), con1024);
+        System.out.println(pi);
+    }
+}