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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6. import java.math.BigInteger;
  7.  
  8. /* Name of the class has to be "Main" only if the class is public. */
  9. class Ideone
  10. {
  11. 	public static void main (String[] args) throws java.lang.Exception
  12. 	{
  13. 		long x = -1501598000831384712L;
  14. 		long y = -735932670715772870L;
  15. 		System.out.println(hex(x) + " * " + hex(y) + " = " + hex(hmul(x, y)));
  16. 	}
  17.  
  18. 	static String hex(long x) {
  19. 		return String.format("0x%016x", x);
  20. 	}
  21.  
  22. static long hmulbigint(long x, long y) {
  23. 	BigInteger c = BigInteger.valueOf(2).pow(64);
  24. 	BigInteger xb = BigInteger.valueOf(x);
  25. 	if (x < 0) xb = xb.add(c);
  26. 	BigInteger yb = BigInteger.valueOf(y);
  27. 	if (y < 0) yb = yb.add(c);
  28. 	BigInteger p = xb.multiply(yb);
  29. 	return p.shiftRight(64).longValue();
  30. }
  31.  
  32. 	static long hmul(long x, long y) {
  33.     // split
  34.     long xl = x & 0xffffffffL;
  35.     long xh = x >>> 32;
  36.     long yl = y & 0xffffffffL;
  37.     long yh = y >>> 32;
  38.     // partial products
  39.     long t00 = xl * yl;
  40.     long t01 = xh * yl;
  41.     long t10 = xl * yh;
  42.     long t11 = xh * yh;
  43.     // resolve carries
  44.     t11 += (t10 >>> 32) + (t01 >>> 32);
  45.     long tc = (t10 & 0xffffffffL) + (t01 & 0xffffffffL) + (t00 >>> 32);
  46.     t11 += tc >>> 32;
  47.     return t11;
  48. }
  49. }
Success #stdin #stdout 0.1s 28064KB
comments (?)
stdin 
Standard input is empty
stdout 
0xeb294092f5023378 * 0xf5c971229761c03a = 0xe1c7861d53e80bf3
https://ideone.com/JlMJva
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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