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Subject: Re: The need to unmake move

Author: Jeremiah Penery

Date: 15:18:15 09/02/03

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On September 02, 2003 at 11:09:21, Robert Hyatt wrote:

>On September 01, 2003 at 23:58:38, Jeremiah Penery wrote:
>
>>On September 01, 2003 at 23:53:20, Robert Hyatt wrote:
>>
>>>It is almost guaranteed that _all_ critical search data for _all_ threads will
>>>be allocated in a single processor's local memory.
>>
>>That would be the worst possible usage of memory.  Why in the world would a
>>program perform like that?
>
>
>Do you understand how parallel programming works?  Suppose you want to
>do this:
>
>TREE  blocks[128];
>
>Where TREE is a big structure.
>
>That puts the blocks into consecutive memory addresses.

That's one part of the critical data structures, but there are more parts that
can get placed elsewhere.

>On a NUMA machine that puts the blocks into one processor's local memory,
>or it might split across two if you are near the end of one's memory.
>
>On a true SMP (non-NUMA) box, that works _perfectly_ and it is the way things
>are done.  On a NUMA box, it sucks.

Then on an SMP machine it gets put into one memory bank, and interleaving can't
be used, and you're still screwed.



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