CalcPi.java

import java.math.BigDecimal;
import java.math.RoundingMode;

class CalcPi {
    public static void main(String[] args) {
        var start = System.currentTimeMillis();
        final long RADIUS = 3000000000L;
        final long RADIUS_E2 = RADIUS * RADIUS;
        long count = 0;
        System.out.println("RADIUS_E2=" + RADIUS_E2);


        long offsetX = RADIUS;
        for (long y = 0;y < RADIUS;y++) {
            long y2 = y * y;
            for (long x = offsetX;x > 0;x--) {
                long distance_e2 = x * x + y2;
                if (distance_e2 < RADIUS_E2) {
                    offsetX = x;
                    count += offsetX;
                    break;
                }
            }
        }
        
        BigDecimal counted2 = new BigDecimal(count);
        BigDecimal devider = new BigDecimal(RADIUS / 2).multiply(new BigDecimal(RADIUS / 2));
        BigDecimal pi = counted2.divide(devider, 50, RoundingMode.HALF_DOWN);
        System.out.println("counted2=" + counted2);
        System.out.println("pi=" + pi);
        // System.out.println(counted / RADIUS / RADIUS);
        System.out.println(System.currentTimeMillis() - start + "ms");
    }
}