82 lines
3.0 KiB
Python
82 lines
3.0 KiB
Python
#!/usr/bin/env python
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#
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# Public Domain 2014-2016 MongoDB, Inc.
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# Public Domain 2008-2014 WiredTiger, Inc.
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#
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# This is free and unencumbered software released into the public domain.
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#
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# Anyone is free to copy, modify, publish, use, compile, sell, or
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# distribute this software, either in source code form or as a compiled
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# binary, for any purpose, commercial or non-commercial, and by any
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# means.
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#
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# In jurisdictions that recognize copyright laws, the author or authors
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# of this software dedicate any and all copyright interest in the
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# software to the public domain. We make this dedication for the benefit
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# of the public at large and to the detriment of our heirs and
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# successors. We intend this dedication to be an overt act of
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# relinquishment in perpetuity of all present and future rights to this
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# software under copyright law.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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# IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
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# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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# OTHER DEALINGS IN THE SOFTWARE.
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# suite_random.py
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# A quick and predictable pseudo random number generator.
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class suite_random:
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"""
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Generate random 32 bit integers that are predictable,
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and use no global state. We use the Multiply-with-carry
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method invented by George Marsaglia, because it is quick
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and easy to implement.
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"""
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def __init__(self, *args):
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arglen = len(args)
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if arglen == 1:
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self.seedw = int(args[0]) & 0xffffffff
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self.seedz = int(args[0]) & 0xffffffff
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elif arglen == 2:
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self.seedw = int(args[0]) & 0xffffffff
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self.seedz = int(args[1]) & 0xffffffff
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else:
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self.seedw = 521288629
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self.seedz = 362436069
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def rand32(self):
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"""
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returns a random 32 bit integer
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"""
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w = self.seedw
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z = self.seedz
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if w == 0 or z == 0:
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self.seedw = 521288629
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self.seedz = 362436069
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self.seedz = (36969 * (z & 65535) + (z >> 16)) & 0xffffffff
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self.seedw = (18000 * (w & 65535) + (w >> 16)) & 0xffffffff
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return ((z << 16) + w & 65535) & 0xffffffff
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def rand_range(self, n, m):
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"""
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returns a random integer in the range [N,M).
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"""
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if m > 0xffffffff or n < 0:
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raise ValueError("rand32_range expects args between 0 , 2^32")
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if n >= m:
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raise ValueError("rand32_range(n,m) expects n < m")
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r = self.rand32()
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return (r % (m - n)) + n
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def rand_float(self):
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"""
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returns a random floating point value between 0 and 1.0
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The number returned does not encompass all possibilities,
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only 2^32 values within the range.
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"""
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return (self.rand32() + 0.0)/0x100000000
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