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package chu_nz_baby;
import java.util.*; import java.math.*;
/** * <p>title:π 圆周率的计算 </p> * <p>description:使用java bigdecimal完成圆周率(chudnovsky公式)的计算。可以指定计算精度和计算参数。 </p> * <p>copyright: copyright (c) 2004</p> * <a href="http://www.jason314.com/palgorithm.htm">圆周率的计算方法#chudnovsky公式</a> * <a href="http://www.oursci.org/magazine/200301/030126.htm">圆周率π的计算历程</a> * @author chu_nz_baby@hotmail.com * @version 1.0 */
public class pi {
private bigdecimal result;
public pi() {
}
public void run(int n, int scale) { if(system.getproperty("debug") != null){ system.out.println("n=" + n); }
bigdecimal upper = new bigdecimal(426880.0000 * math.sqrt(10005.0000)); upper = upper.setscale(scale, bigdecimal.round_half_even);
if(system.getproperty("debug") != null){ system.out.println("upper=" + upper); }
bigdecimal downer = bigdecimal.valueof(0);
for (int i = 0; i <= n; i++) { bigdecimal d0 = factorial(6 * i).multiply ( new bigdecimal( 545140134 * i + 13591409)); bigdecimal d1 = factorial(i); bigdecimal d2 = pow(d1, 3); bigdecimal d3 = factorial(3 * i); bigdecimal d4 = pow(-640320, 3 * i); bigdecimal d5 = d2.multiply(d3); bigdecimal d6 = d4.multiply(d5); bigdecimal d = d0.divide( d6, bigdecimal.round_half_even );
downer = downer.add(d);
}
if(system.getproperty("debug") != null){ system.out.println("downer=" + downer); }
if(system.getproperty("debug") != null){ system.out.println("upper.scale = " + upper.scale()); system.out.println("downer.scale = " + downer.scale()); }
result = upper.divide(downer, bigdecimal.round_half_even);
if(system.getproperty("debug") != null){ system.out.println("result.scale = " + result.scale()); }
}
public bigdecimal getresult() {
return result; }
public static bigdecimal pow(double val, int power){ return pow(new bigdecimal(val), power); }
public static bigdecimal pow(bigdecimal val, int power){ bigdecimal value = bigdecimal.valueof(1); for(int i = 1; i <= power; i ++){ value = value.multiply(val); } return value; }
public static bigdecimal factorial(int n){ bigdecimal value = bigdecimal.valueof(1); for(int i = 1; i <=n ; i++){ value = value.multiply(bigdecimal.valueof(i)); } return value; }
public static void main(string[] args) { if(args.length < 2){ system.out.println("usage: " + "java nz-baby.pi " + " 参数(0-无穷大) 精度(1-4294967296)"); system.out.println("usage: " + "java nz-baby.pi " + " n(0- ) scale(1-4294967296)"); system.exit(-1); }
int n = integer.parseint(args[0]); int scale = integer.parseint(args[1]);
system.out.println("palgorithm n=" + n + " scale=" + scale); system.out.println("start:" + new date(system.currenttimemillis())); pi p = new pi(); p.run(n, scale); system.out.println("end:" + new date(system.currenttimemillis())); system.out.println("result=" + p.getresult()); }
}
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