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Subject: Re: Data on hash table probing and memory bandwidth

Author: Robert Hyatt

Date: 13:31:21 12/16/02

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On December 16, 2002 at 16:03:11, Miguel A. Ballicora wrote:

>On December 16, 2002 at 14:51:18, Robert Hyatt wrote:
>
>>On December 16, 2002 at 13:32:46, Dieter Buerssner wrote:
>>
>>>I did similar tests. IIRC, I got differences of > 5% faster for, what you called
>>>"new". I unfortunately do not have the code for the "old" (2 different tables)
>>>handy anymore, to recheck. You are not probing in quiescence search, so it is
>>>reasonable to expect, that your differences are smaller.
>>>
>>>Anyway, for a very small code change (I would guess not more than 1 hour),
>>>getting 5% is not so bad.
>>>
>>>Regards,
>>>Dieter
>>
>>
>>No, although for me it was 2% which is not so hot...
>>
>>I will probably stick with it since it is done, of course....
>
>Did you make sure that your table is aligned avery 16 bytes and not 8, for
>instance?
>
>Miguel


Yes.  If you look at init.c you will see where I force the starting address to
be a multiple
of 16 regardless of what malloc() gives me.

However, my entries are 16 bytes long, and have three in a "set".  No way to map
a "set" to
the front of a cache line every time.  It is going to be staggered no matter
what...



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