<div class="gmail_quote">On Tue, Mar 15, 2011 at 16:36, Natarajan CS <span dir="ltr"><<a href="mailto:csnataraj@gmail.com">csnataraj@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Also I wonder what percentage of the code is actually blas/lapack intensive to make any significant dent in wall cock?</blockquote></div><br><div>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.</div>