William Stein wrote:
> 2009/6/13 Clint Whaley <wha...@cs.utsa.edu>:
>> The actual error you guys are showing below looks more like something
>> really odd happened during an install: It is trying to choose a small
>> block factor, and has chosen 0. Looking at the place the assertion
>> failed, its GuessSmallNB() in ATLAS/tune/blas/gemm/mmsearch.c,
>> which might freak out like this if mu or nu were chosen to be huge
>> values (the L1 is small, at 8K). To track this down, I'd probably throw
>> in some print statements in GuessSmallNB() to see what part of the
>> computation is failing.
>>
>> If you just want to force it to continue, I think it'd be safe to simply
>> have the routine return(28); as the first statement . . .
>
> Many thanks for that hint!
>
> William
>
>> Cheers,
>> Clint
Hi Clint, William, Casey and anyone else reading this!
I downloaded the ATLAS 3.8.3 source code and built it outside of Sage,
so the following results are directly from your ATLAS source.
This was compiled on a Sun T5240 with 128 virtual processors running at
1167 MHz.
I used all the GNU tools - gcc version 4.4.0, the GNU linker (version
2.15), GNU assembler (version 2.15).
I stuck a few print statements as suggested (see my revised file below).
The outputs were:
Arguments passed to GuessSmallNB were: pre=d L1Size=8192 mu=6 nu=5
L1Size=1024 size=8 imult=30 nb=0
Printing nb for a second time, as it may have changed if it was less
than 28. nb=0
I've not tried changing the code in sage yet so it returns 28. I'll do
that before I go to bed and let it run (its 2326 here in the UK).
Dave
-----------
static int GuessSmallNB(char pre, int L1Size, int mu, int nu)
/*
* Returns a small nb useful for in-cache timings
*/
{
int imult, nb, size;
printf("Arguments passed to GuessSmallNB were: pre=%c L1Size=%d
mu=%d nu=%d\n",pre, L1Size, mu, nu);
size = (pre == 'd' || pre == 'z') ? ATL_dsize : ATL_ssize;
L1Size /= size;
imult = Mylcm(mu, nu);
/*
* Try to get a block factor where A, B & C all fit into cache
*/
for (nb=imult; 3*nb*nb < L1Size; nb += imult);
nb -= imult;
/*
* If block to small, settle for fitting one block comfortably in cache
*/
printf("L1Size=%d size=%d imult=%d nb=%d\n",L1Size, size,imult,nb);
if (nb < 28)
{
for (; nb*nb+(mu+nu)*nb*2 < L1Size; nb += imult);
nb -= imult;
}
printf("Printing nb for a second time, as it may have changed if it
was less than 28. nb=%d\n",nb);
fprintf(stderr, "L1Size=%d, pre=%c, Smallnb=%d\n", L1Size, pre, nb);
assert(nb);
return(nb);
}
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