22 Sep 1998 14:37:53 -0400

Related articles |
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[12 earlier articles] |

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: 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) |

Re: inlining + optimization = nuisance bugs chase@world.std.com (David Chase) (1998-09-22) |

Re: inlining + optimization = nuisance bugs christian.bau@isltd.insignia.com (1998-09-22) |

Re: inlining + optimization = nuisance bugs andrewf@slhosiery.com.au (Andrew Fry) (1998-09-24) |

Re: inlining + optimization = nuisance bugs comments@cygnus-software.com (Bruce Dawson) (1998-09-24) |

Re: inlining + optimization = nuisance bugs Martin.Ward@SMLtd.Com (1998-09-26) |

Re: inlining + optimization = nuisance bugs toon@moene.indiv.nluug.nl (Toon Moene) (1998-09-29) |

Re: inlining + optimization = nuisance bugs wclodius@aol.com (1998-09-29) |

[9 later articles] |

From: | David Chase <chase@world.std.com> |

Newsgroups: | comp.compilers |

Date: | 22 Sep 1998 14:37:53 -0400 |

Organization: | NaturalBridge LLC |

References: | 98-09-071 98-09-096 |

Keywords: | arithmetic |

Zalman Stern wrote:

*> You can say things like "Floating-point is imprecise anyway" and*

*> "Well if you'd just write robust code, this wouldn't happen" but it's*

*> just dancing around the fact that the tools make it (very) difficult*

*> to express a precise algorithm.*

Kahan's term for people promoting this point of view ("if you'd just

write robust code") was "the guilt squad". Luddy's counter- example

in favor of inconsistent use of high precision arithmetic is not a

good one, since every numerical analysis course I ever taken explained

the concept of "machine epsilon" and what would happen if you added

two numbers differing by a more extreme ratio. Machine epsilon

figures into proofs of convergence for many numerical algorithms. (I

took these courses as an undergradual and gradual student, and worked

through some of the proofs.)

In contrast, inconsistent use of higher precision (what you can get

with fused-multiply-add) does not. That it is faster, does not make

it better.

David Chase

NaturalBridge LLC

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