Calculate the floor of the log, base 2
/*
* $RCSfile: MathUtil.java,v $
* $Revision: 1.1 $
* $Date: 2005/02/11 05:02:25 $
* $State: Exp $
*
* Class: MathUtil
*
* Description: Utility mathematical methods
*
*
*
* COPYRIGHT:
*
* This software module was originally developed by Raphal Grosbois and
* Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel
* Askelf (Ericsson Radio Systems AB); and Bertrand Berthelot, David
* Bouchard, Flix Henry, Gerard Mozelle and Patrice Onno (Canon Research
* Centre France S.A) in the course of development of the JPEG2000
* standard as specified by ISO/IEC 15444 (JPEG 2000 Standard). This
* software module is an implementation of a part of the JPEG 2000
* Standard. Swiss Federal Institute of Technology-EPFL, Ericsson Radio
* Systems AB and Canon Research Centre France S.A (collectively JJ2000
* Partners) agree not to assert against ISO/IEC and users of the JPEG
* 2000 Standard (Users) any of their rights under the copyright, not
* including other intellectual property rights, for this software module
* with respect to the usage by ISO/IEC and Users of this software module
* or modifications thereof for use in hardware or software products
* claiming conformance to the JPEG 2000 Standard. Those intending to use
* this software module in hardware or software products are advised that
* their use may infringe existing patents. The original developers of
* this software module, JJ2000 Partners and ISO/IEC assume no liability
* for use of this software module or modifications thereof. No license
* or right to this software module is granted for non JPEG 2000 Standard
* conforming products. JJ2000 Partners have full right to use this
* software module for his/her own purpose, assign or donate this
* software module to any third party and to inhibit third parties from
* using this software module for non JPEG 2000 Standard conforming
* products. This copyright notice must be included in all copies or
* derivative works of this software module.
*
* Copyright (c) 1999/2000 JJ2000 Partners.
* */
/**
* This class contains a collection of utility methods fro mathematical
* operations. All methods are static.
* */
public class MathUtil {
/**
* Method that calculates the floor of the log, base 2,
* of 'x'. The calculation is performed in integer arithmetic,
* therefore, it is exact.
*
* @param x The value to calculate log2 on.
*
* @return floor(log(x)/log(2)), calculated in an exact way.
* */
public static int log2(int x) {
int y,v;
// No log of 0 or negative
if (x <= 0) {
throw new IllegalArgumentException(""+x+" <= 0");
}
// Calculate log2 (it's actually floor log2)
v = x;
y = -1;
while (v>0) {
v >>=1;
y++;
}
return y;
}
}
Related examples in the same category
1. | Absolute value | | |
2. | Find absolute value of float, int, double and long using Math.abs | | |
3. | Find ceiling value of a number using Math.ceil | | |
4. | Find exponential value of a number using Math.exp | | |
5. | Find floor value of a number using Math.floor | | |
6. | Find minimum of two numbers using Math.min | | |
7. | Find power using Math.pow | | |
8. | Find square root of a number using Math.sqrt | | |
9. | Find natural logarithm value of a number using Math.log | | |
10. | Find maximum of two numbers using Math.max | | |
11. | Get the power value | | |
12. | Using the Math Trig Methods | | |
13. | Using BigDecimal for Precision | | |
14. | Demonstrate our own version round() | | |
15. | Demonstrate a few of the Math functions for Trigonometry | | |
16. | Exponential Demo | | |
17. | Min Demo | | |
18. | Basic Math Demo | | |
19. | Using strict math in applications | | |
20. | Conversion between polar and rectangular coordinates | | |
21. | Using the pow() function | | |
22. | Using strict math at the method level | | |
23. | Calculating hyperbolic functions | | |
24. | Calculating trigonometric functions | | |
25. | Weighted floating-point comparisons | | |
26. | Solving right triangles | | |
27. | Applying the quadratic formula | | |
28. | Greatest Common Divisor (GCD) of positive integer numbers | | |
29. | Least Common Multiple (LCM) of two strictly positive integer numbers | | |
30. | Moving Average | | |
31. | Make Exponention | | |
32. | Caclulate the factorial of N | | |
33. | Trigonometric Demo | | |
34. | Complex Number Demo | | |
35. | sqrt(a^2 + b^2) without under/overflow | | |
36. | Returns an integer hash code representing the given double array value. | | |
37. | Returns an integer hash code representing the given double value. | | |
38. | Returns n!. Shorthand for n Factorial, the product of the numbers 1,...,n as a double. | | |
39. | Returns n!. Shorthand for n Factorial, the product of the numbers 1,...,n. | | |
40. | Returns the hyperbolic sine of x. | | |
41. | Contains static definition for matrix math methods. | | |
42. | For a double precision value x, this method returns +1.0 if x >= 0 and -1.0 if x < 0. Returns NaN if x is NaN. | | |
43. | For a float value x, this method returns +1.0F if x >= 0 and -1.0F if x < 0. Returns NaN if x is NaN. | | |
44. | Normalize an angle in a 2&pi wide interval around a center value. | | |
45. | Normalizes an angle to a relative angle. | | |
46. | Normalizes an angle to an absolute angle | | |
47. | Normalizes an angle to be near an absolute angle | | |
48. | Returns the natural logarithm of n!. | | |
49. | Returns the least common multiple between two integer values. | | |
50. | Gets the greatest common divisor of the absolute value of two numbers | | |
51. | Matrix manipulation | | |
52. | Returns exact (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient | | |
53. | Returns a double representation of the (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient | | |
54. | Returns the natural log of the (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient | | |
55. | Returns the hyperbolic cosine of x. | | |
56. | Math Utils | | |
57. | Implements the methods which are in the standard J2SE's Math class, but are not in in J2ME's. | | |
58. | Utility methods for mathematical problems. | | |
59. | A math utility class with static methods. | | |
60. | Computes the binomial coefficient "n over k" | | |
61. | Log Gamma | | |
62. | Log Beta | | |
63. | Beta | | |
64. | Gamma | | |
65. | Factorial | | |
66. | Computes p(x;n,p) where x~B(n,p) | | |
67. | Returns the sum of two doubles expressed in log space | | |
68. | sigmod | | |
69. | sigmod rev | | |
70. | Numbers that are closer than this are considered equal | | |
71. | Returns the KL divergence, K(p1 || p2). | | |
72. | Returns the sum of two doubles expressed in log space | | |
73. | Returns the difference of two doubles expressed in log space | | |
74. | Is Prime | | |
75. | Statistical functions on arrays of numbers, namely, the mean, variance, standard deviation, covariance, min and max | | |
76. | This class calculates the Factorial of a numbers passed into the program through command line arguments. | | |
77. | Calculates the Greatest Common Divisor of two numbers passed into the program through command line arguments. | | |
78. | Variance: the square of the standard deviation. | | |
79. | Population Standard Deviation | | |
80. | Returns from a static prime table the least prime that is greater than or equal to a specified value. | | |