New submission from Ma Lin <malin...@163.com>:
lzma/bz2 modules are using the same buffer growth algorithm: [1][2]
newsize = size + (size >> 3) + 6;
lzma/bz2 modules' default output buffer is 8192 bytes [3][4], so the growth
step is below.
For many cases, maybe the buffer is resized too many times.
Is it possible to design a new growth algorithm that grows faster when the size
is not very large.
1: 8,196 bytes
2: 9,226 bytes
3: 10,385 bytes
4: 11,689 bytes
5: 13,156 bytes
6: 14,806 bytes
7: 16,662 bytes
8: 18,750 bytes
9: 21,099 bytes
10: 23,742 bytes
11: 26,715 bytes
12: 30,060 bytes
13: 33,823 bytes
14: 38,056 bytes
15: 42,819 bytes
16: 48,177 bytes
17: 54,205 bytes
18: 60,986 bytes
19: 68,615 bytes
20: 77,197 bytes
21: 86,852 bytes
22: 97,714 bytes
23: 109,934 bytes
24: 123,681 bytes
25: 139,147 bytes
26: 156,546 bytes
27: 176,120 bytes
28: 198,141 bytes
29: 222,914 bytes
30: 250,784 bytes
31: 282,138 bytes
32: 317,411 bytes
33: 357,093 bytes
34: 401,735 bytes
35: 451,957 bytes
36: 508,457 bytes
37: 572,020 bytes
38: 643,528 bytes
39: 723,975 bytes
40: 814,477 bytes
41: 916,292 bytes
42: 1,030,834 bytes
43: 1,159,694 bytes
44: 1,304,661 bytes
45: 1,467,749 bytes
46: 1,651,223 bytes
47: 1,857,631 bytes
48: 2,089,840 bytes
49: 2,351,076 bytes
50: 2,644,966 bytes
51: 2,975,592 bytes
52: 3,347,547 bytes
53: 3,765,996 bytes
54: 4,236,751 bytes
55: 4,766,350 bytes
56: 5,362,149 bytes
57: 6,032,423 bytes
58: 6,786,481 bytes
59: 7,634,797 bytes
60: 8,589,152 bytes
61: 9,662,802 bytes
62: 10,870,658 bytes
63: 12,229,496 bytes
64: 13,758,189 bytes
65: 15,477,968 bytes
66: 17,412,720 bytes
67: 19,589,316 bytes
68: 22,037,986 bytes
69: 24,792,740 bytes
70: 27,891,838 bytes
71: 31,378,323 bytes
72: 35,300,619 bytes
73: 39,713,202 bytes
74: 44,677,358 bytes
75: 50,262,033 bytes
76: 56,544,793 bytes
77: 63,612,898 bytes
78: 71,564,516 bytes
79: 80,510,086 bytes
80: 90,573,852 bytes
81: 101,895,589 bytes
82: 114,632,543 bytes
83: 128,961,616 bytes
84: 145,081,824 bytes
85: 163,217,058 bytes
86: 183,619,196 bytes
87: 206,571,601 bytes
88: 232,393,057 bytes
89: 261,442,195 bytes
90: 294,122,475 bytes
91: 330,887,790 bytes
92: 372,248,769 bytes
93: 418,779,871 bytes
94: 471,127,360 bytes
95: 530,018,286 bytes
96: 596,270,577 bytes
97: 670,804,405 bytes
98: 754,654,961 bytes
99: 848,986,837 bytes
100: 955,110,197 bytes
[1] lzma buffer growth algorithm:
https://github.com/python/cpython/blob/v3.9.0b4/Modules/_lzmamodule.c#L133
[2] bz2 buffer growth algorithm:
https://github.com/python/cpython/blob/v3.9.0b4/Modules/_bz2module.c#L121
[3] lzma default buffer size:
https://github.com/python/cpython/blob/v3.9.0b4/Modules/_lzmamodule.c#L124
[4] bz2 default buffer size:
https://github.com/python/cpython/blob/v3.9.0b4/Modules/_bz2module.c#L109
----------
components: Library (Lib)
messages: 373454
nosy: malin
priority: normal
severity: normal
status: open
title: lzma/bz2 module: inefficient buffer growth algorithm
type: performance
versions: Python 3.10
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue41265>
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