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

[Smith, Barry F.]

  I would like a mode for the PETSc matrix classes where the values are simply shipped to and used on the GPU in single precision. In theory it is trivial to implement.


> On Jul 11, 2019, at 3:31 PM, Jed Brown via petsc-dev <petsc-dev at mcs.anl.gov> wrote:
> 
> "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.