[petsc-users] Reductions in various vector and matrix kernels

[Jed Brown]

"R. Oğuz Selvitopi" <roguzsel at gmail.com> writes:

> It seems PETSc performs additional checks that require extra communication
> in VecAXPY/VecAYPX as well as in MatMultTranspose when built with debug
> option.

That's why it's called "debug".  The checks are to make sure that
logically collective information is indeed collective.  The man pages
state "logically collective" and debug builds verify most things.

> It does not perform any communication in the kernels I have mentioned in
> the optimized build.

Correct.
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