10 Dec 1991 06:51:44 GMT

Related articles |
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Definition of Data Dependence Distance pugh@cs.umd.edu (1991-12-06) |

Re: Definition of Data Dependence Distance maydan@Neon.Stanford.EDU (1991-12-06) |

Re: Definition of Data Dependence Distance frazier@CS.UCLA.EDU (1991-12-06) |

Re: Definition of Data Dependence Distance grover@brahmand.Eng.Sun.COM (1991-12-10) |

Newsgroups: | comp.parallel,comp.compilers |

From: | grover@brahmand.Eng.Sun.COM (Vinod Grover) |

Keywords: | optimize, parallel |

Organization: | Sun Microsystems, Mt. View, Ca. |

References: | 91-12-041 |

Date: | 10 Dec 1991 06:51:44 GMT |

In article 91-12-041 pugh@cs.umd.edu (Bill Pugh) writes:

*>*

*> Does dependence distance represent the difference in the values of *

*> the loop variables, or the difference in the loop trip counts?*

I think the answer depends on why the compiler needs to know the dependence

distance. If one is interested in doing software pipelining or loop

unrolling, then you would care about the "iteration distance", becuase you

are interested in scheduling as many iterations as possible without

encountering a dependence.

If, on the other and, you are interested in doing a data-locality

transformation, you care about the "index-variable distance". Essentially

this requires knowing the distance between memory references.

Many compilers just normalize the loop and punt the whole issue.

Vinod Grover

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