[petsc-dev] Shifting in ICC, changes?

[Hong Zhang]

Jed,

We replaced old numerical factorization and MatSolve with faster data structure,
then cleaned up MatPivotCheck() (still using previous algorithm).
Changes, such as
changeset:   15909:fbc1ba94d8d9
user:        hong at hong-zhangs-macbook-air.local
date:        Wed May 12 22:17:30 2010 -0500
files:       src/mat/impls/aij/seq/aijfact.c
description:
replace macros with inline function MatPivotCheck() for inplace lu (aij format)

could accelerate performance.

Hong


On Fri, Dec 3, 2010 at 4:55 AM, Jed Brown <jed at 59a2.org> wrote:
> What exactly changed between Feb 1 and the petsc-3.1 release with respect to
> shifting (including for (S)BAIJ).  In Feb, I saw negative pivots and blamed
> certain performance characteristics on it.  Now I don't see them, despite
> the fact that SBAIJ does not implement the same shifts that AIJ does.  The
> performance now (or with 3.1) is significantly better, but I would like to
> be able to explain what's going on.  Running with -pc_factor_shift_type none
> is still working much better than Feb 1 -dev and I would like to know why.
> Jed