Re: Compiling code for EM64T

[Guy Coates]

>
> We do care about the performance of the code as we need to get timing
> values on the architecture. Would it be possible to run the intel C/F77
> compilers on opterons to compile optimized for EMT.

Yes; that should work quite nicely.

Unfortunately, the Intel compiler does not have a good track record on
playing nicely with opterons. v8.0 of the compiler could produce binaries
which checked to see if they were running on an non-intel cpu (like an
opteron) and then refuse to run.

Take a look at this thread here:

http://groups-beta.google.com/group/comp.arch/browse_frm/thread/4e42f16511cf8640?hl=en&lr=&rnum=1&prev=/groups%3Fdq%3D%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26group%3Dcomp.arch%26selm%3Da13e403a.0402091438.14018f5a%2540posting.google.com


However, this behaviour is runtime, and not compile time.

Of course, if you are cynical or paranoid enough, and you should probably
run the compiler on your EMT box and on the opteron and compare the
results to make sure that the compiler doesn't do anything nasty when it
finds it is running on an opteron.

Guy



>As for the kernel we
> would have to compile our own kernel anyway as we need custom kernels on
> those machines anyway to support the work we are doing.
>
> Thanks,
>
> Bharath
>
> ---
> Bharath Ramesh   <[EMAIL PROTECTED]>   
> http://csgrad.cs.vt.edu/~bramesh
>
>
>
>

-- 
Dr. Guy Coates,  Informatics System Group
The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
Tel: +44 (0)1223 834244 ex 7199


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Re: Compiling code for EM64T

[Guy Coates]

>What I want to know is that do I need to set up cross compilation or
>normal binary would run without any problem on the EM64T.


The opteron optimised binaries should run fine on EMT64.[1]

However, they may not run as quickly as binaries optimised compiled up
with EMT64 optimisations.  So if you have some code whose performance you
really care about, it is probably worth re-compiling with EMT64 specific
binaries. (Take a look at the intel C/F77 compilers, they can do
significantly better than gcc on some code.)


Cheers,

Guy


[1] The only problem we've had running pure64 on EMT is that 2.6.X kernels
configured for EMT64 do not boot on our machines (IBM HS20 8843s), but
opteron kernels do.


-- 
Dr. Guy Coates,  Informatics System Group
The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
Tel: +44 (0)1223 834244 ex 7199


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