# Re: Compiler optimization and floating point operations

## glen herrmannsfeldt <gah@ugcs.caltech.edu>

Thu, 24 Oct 2013 20:21:21 +0000 (UTC)

*From comp.compilers*

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**From: ** | glen herrmannsfeldt <gah@ugcs.caltech.edu> |

**Newsgroups: ** | comp.compilers |

**Date: ** | Thu, 24 Oct 2013 20:21:21 +0000 (UTC) |

**Organization: ** | Aioe.org NNTP Server |

**References: ** | 13-10-026 13-10-029 |

**Keywords: ** | arithmetic, administrivia, comment |

**Posted-Date: ** | 24 Oct 2013 16:46:37 EDT |

(snip, John wrote)

*> [I think you mean they're not associative. I don't know any*

*> situations where a+b != b+a, but lots where a+(b+c) != (a+b)+c -John]*

I don't know of any with non-commutative addition, but there were

some Cray machines with non-commutative multiply.

For many Cray applications, getting a close answer fast is better

than the exact answer slow.

-- glen

[Oh, right. Can we safely assume that arithmetic model is dead? -John]

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