Re: dgemm performance dependance from CacheEdge value

In message from Clint Whaley <whaley@...> (Fri, 08
Aug 2008 09:12:57 -0500):
>>I performed simultaneous installation of 4 atlas 3.9.1 examplars on
>>Opteron 2350.
>>The CacheEdge value obtained was 384K and 512K (depending from
>>build/tune thread).
>
>Not sure what 4 simult installs is supposed to do for you.  If you
>want to
>tune for parallel performance, then I recommend:
>   http://math-atlas.sourceforge.net/errata.html#SMPCE

Thanks ! It's better approach than my :-)

>>OK, 512K is that I want: 512= size(L3)/4.
>Not sure that CE is hitting the shared L3: I would guess the L2 . . .

  ATLAS3.9.0:
    STAGE 2-1-2: CacheEdge DETECTION
       CacheEdge set to 2621440 bytes
=================^IMHO it's L3 ^ ============

or from dMMCACHEEDGE.LOG:

gemm xdfindCE -f res/atlas_cacheedg
e.h
TA  TB       M       N       K   alpha    beta  CacheEdge       TIME
   MFLOPS
==  ==  ======  ======  ======  ======  ======  =========  =========
 ========

  T   N    1600    1600    1600    1.00    1.00          0      1.228
  6671.69
  T   N    1600    1600    1600    1.00    1.00         16     -2.000
     0.00
  T   N    1600    1600    1600    1.00    1.00         32     -2.000
     0.00
  T   N    1600    1600    1600    1.00    1.00         64      1.514
  5409.95
  T   N    1600    1600    1600    1.00    1.00        128      1.279
  6405.71
  T   N    1600    1600    1600    1.00    1.00        256      1.248
  6565.56
  T   N    1600    1600    1600    1.00    1.00        512      1.239
  6610.67
  T   N    1600    1600    1600    1.00    1.00       1024      1.227
  6673.78
  T   N    1600    1600    1600    1.00    1.00       2048      1.227
  6673.98
  T   N    1600    1600    1600    1.00    1.00       4096      1.227
  6674.22
  T   N    1600    1600    1600    1.00    1.00       8192      1.228
  6672.71

Initial CE=4096KB, mflop=6674.22

  T   N    1600    1600    1600    1.00    1.00       3072      1.227
  6674.70
  T   N    1600    1600    1600    1.00    1.00       2560      1.227
  6676.11
  T   N    1600    1600    1600    1.00    1.00       2304      1.227
  6674.23
  T   N    1600    1600    1600    1.00    1.00       2816      1.227
  6675.75

Best CE=2560KB, mflop=6676.11
====================================================================

This 3.9.0 data were the reason why I thought about using of L3 for
CE.

L2 is also for victims from L1 only. But looking on obtained CE value
- about 2 MB ! - I thought about L3.

> If you
>use
>3.9.1, ATLAS has a kernel that targets the K10h (with prefetch) more
>effectively.  I am presently working on 3.9.2, which should be out
>next
>week at the latest.  In the meantime, if you want to use 3.9.1, be
>sure
>to apply the bug fixes documented at:
>   http://sourceforge.net/tracker/index.php?func=detail&aid=2024948&group_id=23725&atid=379482

I tuned CE w/4 similtaneous installations w/3.9.1. There was no like
hangup , although 1 of 4 installations finished w/some error.

Yours
Mikhail


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