fork download
copy 
  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12. 		// your code goes here
  13. //	}
  14.  
  15. // https://stackoverflow.com/questions/44008357/adding-and-subtracting-exact-values-to-float
  16.  
  17. //public class Toy {
  18. //    public static void main(String args[]) {
  19.         int length = 0x82000000;
  20.         int x = length >>> 24;
  21.         int y = (length >>> 24) & 0xFF;
  22.  
  23.         System.out.println("length = " + length + ", x = " + x + ", y = " + y);
  24.  
  25.         float float0 = 1.5f;
  26.         float float1 = 1.5000001f;
  27.         float float2 = 1.5000002f;
  28.         float float4 = 1.5000004f;
  29.         float float5 = 1.5000005f;
  30.  
  31.         // testLeaps(float0, float4);
  32.         // testLeaps(0, float5);
  33.         // testLeaps(0, -float1);
  34.         // testLeaps(-float1, 0);
  35.  
  36.         System.out.println(Math.nextAfter(-float1, Float.POSITIVE_INFINITY));
  37.         System.out.println(INT_POWER_MASK & Float.floatToIntBits(-float0));
  38.         System.out.println(INT_POWER_MASK & Float.floatToIntBits(float0));
  39.         // testLeaps(-float1, -float0);
  40.         testLeaps(-float0, 0);
  41.         testLeaps(float0, 0);
  42.     }
  43.  
  44.     public static void testLeaps(float value, float destination) {
  45.         System.out.println("optLeaps(" + value + ", " + destination + ") = " + optLeaps(value, destination));
  46.         System.out.println("getLeaps(" + value + ", " + destination + ") = " + getLeaps(value, destination));
  47.     }
  48.  
  49.     public static final int INT_POWER_MASK = 0x7f800000 | 0x007fffff; // ~0x80000000
  50.     /**
  51.      * Retrieves the integer difference between two float-point values according to
  52.      * the IEEE 754 floating-point "single format" bit layout.
  53.      * 
  54.      * <pre>
  55.      * mask 0x80000000 | 0x7f800000            | 0x007fffff
  56.      *            sign | exponent (8 bits)     | coefficient/significand/mantissa/fraction (23 bits) 
  57.      *              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  58.      *              |  |                       |                                                                    |
  59.      *              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
  60.      *               31 30                   23 22                                                                 0
  61.      * 0x7fc00000 => NaN
  62.      * 0x7f800000 +Infinity
  63.      * 0xff800000 -Infinity
  64.      * </pre>
  65.      * 
  66.      * Using base (radix) 10, the numerical value of such a float type number is
  67.      * `(-1)^sign x coefficient x 10^exponent`, so the coefficient is a key factor
  68.      * to calculation of leaps coefficient.
  69.      * 
  70.      * @param value       the first operand
  71.      * @param destination the second operand
  72.      * @return the integer span from {@code value} to {@code destination}
  73.      * @see <a href="https://e...content-available-to-author-only...a.org/wiki/Single-precision_floating-point_format">sign.exponent.mantissa</a>
  74.      */
  75.     public static int optLeaps(float value, float destination) {
  76.         // TODO process possible cases for some special inputs.
  77.  
  78.         int valueBits = Float.floatToIntBits(value); // IEEE 754 floating-point "single format" bit layout
  79.         int destinationBits = Float.floatToIntBits(destination); // IEEE 754 floating-point "single format" bit layout
  80.         int leaps; // Float.intBitsToFloat();
  81.         if ((destinationBits ^ valueBits) >= 0) {
  82.             leaps = Math.abs(destinationBits - valueBits);
  83.         } else {
  84.             leaps = (INT_POWER_MASK & destinationBits) + (INT_POWER_MASK & valueBits);
  85.         }
  86.         return leaps;
  87.     }
  88.  
  89.     public static int getLeaps(float value, float destination) {
  90.         int leaps = 0;
  91.         float signum = Math.signum(destination - value);
  92.  
  93.         // float direction = Float.POSITIVE_INFINITY * signum;
  94.         // while (value * signum < destination * signum) {
  95.         // value = Math.nextAfter(value, direction); // Float.POSITIVE_INFINITY * direction
  96.         // leaps++;
  97.         // }
  98.  
  99.         if (0 == signum) {
  100.             return 0;
  101.         }
  102.         if (0 < signum) {
  103.             while (value < destination) {
  104.                 value = Math.nextAfter(value, Float.POSITIVE_INFINITY);
  105.                 leaps++;
  106.             }
  107.         } else {
  108.             while (value > destination) {
  109.                 value = Math.nextAfter(value, Float.NEGATIVE_INFINITY);
  110.                 leaps++;
  111.             }
  112.         }
  113.         return leaps;
  114.     }
  115.  
  116.     // may optimiaze to reduce the elapsed time by roughly half
  117. //}
  118. }
Time limit exceeded #stdin #stdout 5s 2317312KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
length = -2113929216, x = 130, y = 130
-1.5
1069547520
1069547520
optLeaps(-1.5, 0.0) = 1069547520
getLeaps(-1.5, 0.0) = 1069547520
optLeaps(1.5, 0.0) = 1069547520
https://ideone.com/4j96Ul
Adding and subtracting exact values to float?

Retrieves the integer difference between two float-point values according to the IEEE 754 floating-point "single format" bit layout.
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!