[petsc-dev] [Radev, Martin] Re: Adding a new encoding for FP data

[Jed Brown]

"Zhang, Junchao" <jczhang at mcs.anl.gov> writes:

> A side question: Do lossy compressors have value for PETSc?

Perhaps if they're very fast, but I think it's usually not PETSc's place
to be performing such compression due to tolerances being really subtle.

There certainly is a place for preconditioning using reduced precision.
PETSc used to have MatScalar to store Mat entries in reduced (single)
precision while MFFD Jacobian application and Krylov work stayed in
double.  That was used in FUN3D papers circa 2000 and was "successful",
but rarely used in practice (PETSc had to be built a special way) and
removed due to the maintenance burden.  I think there would be interest
in a runtime option to compress matrix entries.  For regular stencil
operations where they may be a lot of redundancy, such compression could
be lossless.  For general problems, simply working in reduced precision
would be enough.