[petsc-users] Building with MKL 10.3

[Natarajan CS]

Thanks for the clarification Jed. I am involved in numerical software
development but never have come across code that drastically changes
performance based on blas/lapack implementation (for exactly the same reason
you mentioned), so I was trying to learn what the issue might be. I
certainly agree with your comment on HT, the idea is to maintain
computational throughput, I guess if you have a high ILP or full registers
it really doesn't help!


On Tue, Mar 15, 2011 at 10:48 AM, Jed Brown <jed at 59a2.org> wrote:

> On Tue, Mar 15, 2011 at 16:36, Natarajan CS <csnataraj at gmail.com> wrote:
>
>> Also I wonder what percentage of the code is actually blas/lapack
>> intensive to make any significant dent in wall cock?
>
>
> Rather little of PETSc is dependent on dense linear algebra. Some
> third-party direct solvers use it in their numerical factorization routines.
> Otherwise, it's mostly just vector operations which tend to be bandwidth
> limited anyway and are not so sensitive to implementation. Also, it is much
> more common for the majority of run time to be in matrix kernels than pure
> vector operations. Note that while HT is effective at covering stalls due to
> irregular memory access, it's not so good for tight kernels or purely
> bandwidth-limited tasks.
>
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