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Re: Bug in floating point multiplication

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From Robin Becker <robin@reportlab.com>
Subject Re: Bug in floating point multiplication
Date Thu, 02 Jul 2015 16:29:40 +0100
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$ uname -a
Linux everest 4.0.6-1-ARCH #1 SMP PREEMPT Tue Jun 23 14:40:31 CEST 2015 i686 
GNU/Linux
robin@everest:~
$ python2
Python 2.7.10 (default, May 26 2015, 04:28:58)
[GCC 5.1.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
 >>> x = 1.0 - 1.0/2**53
 >>> assert x == 0.9999999999999999
 >>> for i in range(1, 1000000):
...     if int(i*x) == i:
...         print(i); break
...
2049
 >>>
robin@everest:~
$ python
Python 3.4.3 (default, Mar 26 2015, 07:36:01)
[GCC 4.9.2 20150304 (prerelease)] on linux
Type "help", "copyright", "credits" or "license" for more information.
 >>>
KeyboardInterrupt
 >>> x = 1 - 1/2**53
 >>> assert x == 0.9999999999999999
 >>>  for i in range(1, 1000000):
   File "<stdin>", line 1
     for i in range(1, 1000000):
     ^
IndentationError: unexpected indent
 >>> for i in range(1, 1000000):
...     if int(i*x) == i:
...          print(i); break
...
2049
 >>>
robin@everest:~/devel/filps




-- 
Robin Becker

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Thread

Bug in floating point multiplication Steven D'Aprano <steve@pearwood.info> - 2015-07-03 00:52 +1000
  Re: Bug in floating point multiplication Michael Poeltl <michael.poeltl@univie.ac.at> - 2015-07-02 17:10 +0200
  Re: Bug in floating point multiplication Chris Angelico <rosuav@gmail.com> - 2015-07-03 01:21 +1000
  Re: Bug in floating point multiplication Robin Becker <robin@reportlab.com> - 2015-07-02 16:24 +0100
  Re: Bug in floating point multiplication Paul Rubin <no.email@nospam.invalid> - 2015-07-02 08:26 -0700
    Re: Bug in floating point multiplication Chris Angelico <rosuav@gmail.com> - 2015-07-03 01:34 +1000
      Re: Bug in floating point multiplication Steven D'Aprano <steve@pearwood.info> - 2015-07-03 01:41 +1000
    Re: Bug in floating point multiplication Ian Kelly <ian.g.kelly@gmail.com> - 2015-07-02 09:38 -0600
  Re: Bug in floating point multiplication Vincent Vande Vyvre <vincent.vande.vyvre@telenet.be> - 2015-07-02 17:15 +0200
  Re: Bug in floating point multiplication Ian Kelly <ian.g.kelly@gmail.com> - 2015-07-02 09:28 -0600
  Re: Bug in floating point multiplication Robin Becker <robin@reportlab.com> - 2015-07-02 16:29 +0100
  Re: Bug in floating point multiplication Ian Kelly <ian.g.kelly@gmail.com> - 2015-07-02 09:32 -0600
  Re: Bug in floating point multiplication Steven D'Aprano <steve@pearwood.info> - 2015-07-03 01:42 +1000
  Re: Bug in floating point multiplication duncan smith <buzzard@invalid.invalid> - 2015-07-02 17:08 +0100
  Re: Bug in floating point multiplication MRAB <python@mrabarnett.plus.com> - 2015-07-02 17:20 +0100
  Re: Bug in floating point multiplication Tim Chase <python.list@tim.thechases.com> - 2015-07-02 11:59 -0500
  Re: Bug in floating point multiplication Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2015-07-02 19:49 +0200
    Re: Bug in floating point multiplication Ned Deily <nad@acm.org> - 2015-07-02 22:07 -0700
      Re: Bug in floating point multiplication Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2015-07-03 18:27 +0200
  Re: Bug in floating point multiplication Laurent Pointal <laurent.pointal@free.fr> - 2015-07-02 23:12 +0200
  Re: Bug in floating point multiplication Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-07-03 16:13 +0100
  Re: Bug in floating point multiplication Laura Creighton <lac@openend.se> - 2015-07-05 00:54 +0200
  Re: Bug in floating point multiplication Peter Otten <__peter__@web.de> - 2015-07-05 09:38 +0200

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