20 Aug 1998 13:56:26 -0400

Related articles |
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[6 earlier articles] |

Re: inlining + optimization = nuisance bugs darcy@usul.CS.Berkeley.EDU (1998-08-13) |

Re: inlining + optimization = nuisance bugs joachim.durchholz@munich.netsurf.de (Joachim Durchholz) (1998-08-17) |

Re: inlining + optimization = nuisance bugs lindahl@cs.virginia.edu (1998-08-19) |

Re: inlining + optimization = nuisance bugs jfc@mit.edu (1998-08-19) |

Re: inlining + optimization = nuisance bugs joachim.durchholz@munich.netsurf.de (Joachim Durchholz) (1998-08-19) |

Re: inlining + optimization = nuisance bugs roy@prism.gatech.edu (1998-08-20) |

Re: inlining + optimization = nuisance bugs awf@robots.ox.ac.uk (Andrew Fitzgibbon) (1998-08-20) |

Re: inlining + optimization = nuisance bugs bear@sonic.net (Ray Dillinger) (1998-08-22) |

Re: numerical methods sources chase@world.std.com (David Chase) (1998-08-24) |

Re: inlining + optimization = nuisance bugs luddy@concmp.com (Luddy Harrison) (1998-09-18) |

Re: inlining + optimization = nuisance bugs cfc@world.std.com (Chris F Clark) (1998-09-19) |

Re: inlining + optimization = nuisance bugs luddy@concmp.com (Luddy Harrison) (1998-09-22) |

Re: inlining + optimization = nuisance bugs zalman@netcom.com (1998-09-22) |

[16 later articles] |

From: | Andrew Fitzgibbon <awf@robots.ox.ac.uk> |

Newsgroups: | comp.compilers |

Date: | 20 Aug 1998 13:56:26 -0400 |

Organization: | Oxford University Robotics Group |

References: | 98-08-056 98-08-085 |

Keywords: | arithmetic, standards |

*> [I've never understood why people are so eager to have fast wrong*

*> answers. -John]*

Sometimes the IEEE is a little more pedantic than one wants. I don't care

if 0.0/0.0 trashes my hard disk, I won't let it happen. Similarly, if

ripple in the last digit makes a difference to my code, it's not robust

enough.

Of course correct should be the default, but I'm just making the point

that "fast wrong" should always be an option.

It *is* difficult to say how wrong, though. In some sense there's a

hierarchy like:

undefined exception behaviour on 0/0 or sqrt(-1)

simplifying "1.0 * x" to "x"

transforming "(a + b) + c" into "a + (b + c)"

transforming "vector /= 3.0" with "vector *= (1/3.0)"

nonrepeatable behaviour

silently treating doubles as singles.

Different people stop at different levels, and reorder the list.

--

Andrew Fitzgibbon, awf@robots.ox.ac.uk

Oxford Information Engineering Research Group +44 01865 273127

<a href=http://www.robots.ox.ac.uk/~awf> Home Page </a>

--

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