Beefy Boxes and Bandwidth Generously Provided by pair Networks
Syntactic Confectionery Delight
 
PerlMonks  

Re^6: The 10**21 Problem (Part 3)

by eyepopslikeamosquito (Canon)
on May 17, 2014 at 23:13 UTC ( #1086471=note: print w/ replies, xml ) Need Help??


in reply to Re^5: The 10**21 Problem (Part 3)
in thread The 10**21 Problem (Part 3)

There's no need to align the prefetch pointer.
Whoops, yes you are right. I made a silly mistake in my original test; with that blunder fixed, with your version, there is no difference in running speed (both run in 38 seconds).

Curiously, my version runs in 37 seconds with:

_mm_prefetch(&bytevecM[(unsigned int)m7 & 0xffffff80], _MM_HINT_T0); _mm_prefetch(&bytevecM[64+((unsigned int)m7 & 0xffffff80)], _MM_HINT_T +0);
versus 40 seconds with:
_mm_prefetch(&bytevecM[(unsigned int)m7], _MM_HINT_T0); _mm_prefetch(&bytevecM[(unsigned int)m7 ^ 64], _MM_HINT_T0);
I have no explanation for that, unless perhaps the prefetcher likes to prefetch in order (?).

Thanks for the other tips. Optimizing for the prefetcher seems to be something of a dark art -- if you know of any cool links on that, please let me know.


Comment on Re^6: The 10**21 Problem (Part 3)
Select or Download Code

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1086471]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others meditating upon the Monastery: (12)
As of 2014-07-28 22:14 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    My favorite superfluous repetitious redundant duplicative phrase is:









    Results (210 votes), past polls