source file: /home/buildslave/tahoe/edgy/build/src/allmydata/util/mathutil.py
file stats: 36 lines, 36 executed: 100.0% covered
1. # Copyright (c) 2005-2007 Bryce "Zooko" Wilcox-O'Hearn
2. # mailto:zooko@zooko.com
3. # http://zooko.com/repos/pyutil
4. # Permission is hereby granted, free of charge, to any person obtaining a copy
5. # of this work to deal in this work without restriction (including the rights
6. # to use, modify, distribute, sublicense, and/or sell copies).
7.
8. """
9. A few commonly needed functions.
10. """
11.
12. import math
13.
14. def div_ceil(n, d):
15. """
16. The smallest integer k such that k*d >= n.
17. """
18. return (n/d) + (n%d != 0)
19.
20. def next_multiple(n, k):
21. """
22. The smallest multiple of k which is >= n.
23. """
24. return div_ceil(n, k) * k
25.
26. def pad_size(n, k):
27. """
28. The smallest number that has to be added to n so that n is a multiple of k.
29. """
30. if n%k:
31. return k - n%k
32. else:
33. return 0
34.
35. def is_power_of_k(n, k):
36. return k**int(math.log(n, k) + 0.5) == n
37.
38. def next_power_of_k(n, k):
39. if n == 0:
40. x = 0
41. else:
42. x = int(math.log(n, k) + 0.5)
43. r = k**x
44. if k**x < n:
45. return k**(x+1)
46. else:
47. return k**x
48.
49. def ave(l):
50. return sum(l) / len(l)
51.
52. def log_ceil(n, b):
53. """
54. The smallest integer k such that b^k >= n.
55.
56. log_ceil(n, 2) is the number of bits needed to store any of n values, e.g.
57. the number of bits needed to store any of 128 possible values is 7.
58. """
59. p = 1
60. k = 0
61. while p < n:
62. p *= b
63. k += 1
64. return k
65.
66. def log_floor(n, b):
67. """
68. The largest integer k such that b^k <= n.
69. """
70. p = 1
71. k = 0
72. while p <= n:
73. p *= b
74. k += 1
75. return k - 1