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| author | Guido van Rossum <guido@python.org> | 1998-05-29 17:51:59 (GMT) |
|---|---|---|
| committer | Guido van Rossum <guido@python.org> | 1998-05-29 17:51:59 (GMT) |
| commit | cc20b76ad00d5932eda124a49818c0af4265d3d4 (patch) | |
| tree | 2c0112a1d92d1fdfced6bb0fb66b9c418622c4d5 | |
| parent | d03e1197cb5052e3f758794e2a7aecf9f5ca5f46 (diff) | |
| download | cpython-cc20b76ad00d5932eda124a49818c0af4265d3d4.zip cpython-cc20b76ad00d5932eda124a49818c0af4265d3d4.tar.gz cpython-cc20b76ad00d5932eda124a49818c0af4265d3d4.tar.bz2 | |
Add comments explaining thread unsafety of this code.
| -rw-r--r-- | Lib/whrandom.py | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Lib/whrandom.py b/Lib/whrandom.py index 95e88f3..7f33fd6 100644 --- a/Lib/whrandom.py +++ b/Lib/whrandom.py @@ -29,6 +29,13 @@ # Adrian Baddeley. +# Multi-threading note: the random number generator used here is not +# thread-safe; it is possible that nearly simultaneous calls in +# different theads return the same random value. To avoid this, you +# have to use a lock around all calls. (I didn't want to slow this +# down in the serial case by using a lock here.) + + class whrandom: # # Initialize an instance. @@ -60,6 +67,8 @@ class whrandom: # Get the next random number in the range [0.0, 1.0). # def random(self): + # This part is thread-unsafe: + # BEGIN CRITICAL SECTION x, y, z = self._seed # x = (171 * x) % 30269 @@ -67,6 +76,7 @@ class whrandom: z = (170 * z) % 30323 # self._seed = x, y, z + # END CRITICAL SECTION # return (x/30269.0 + y/30307.0 + z/30323.0) % 1.0 # |