[petsc-dev] MATLMVM

[Munson, Todd]

I would be happy with one matrix type and removing the convenience functions
from the code.  I am surprised that the dark lord did not mention it when
he approved the pull request...

Matt: the difference in the subtypes is that they are using different formulas 
that result in different approximations.  BFGS is for symmetric problems and 
is a rank-2 update that maintains positive definiteness, SR1 is for 
symmetric problems and is a rank-1 update that can be indefinite.

The nonsymmetric equivalents (BadBroyden and GoodBroyden) are also different 
and bad Broyden is typically better than good Broyden.

Performance on a particular problem varies greatly depending on both the
specific problem and the approximation type selected.

Recall to get performance, you can either make the computational kernels
run faster, change the algorithm, or both.  Changing the matrix 
approximations changes the algorithm.

Todd.

> On Sep 11, 2018, at 10:12 AM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Tue, Sep 11, 2018 at 9:47 AM Dener, Alp <adener at anl.gov> wrote:
> 1 base type and 8 subtypes. If there’s a better convention/structure to do this in PETSc, I’d be happy to get a refactoring done ASAP this week so that it’s cleaner in the release.
> 
> I guess what Lisandro is asking is, what backend differences are there to make so many type necessary.
> 
> Looking at the few I recognize, it seems like they encode the sum of rank 1 matrices (BFGS, SR1). Why
> would we have separate types for this two things?
> 
>   Thanks,
> 
>      Matt
>  
> —
> Alp Dener
> Argonne National Laboratory
> https://mcs.anl.gov/person/alp-Dener
> 
> On Sep 11, 2018, at 5:10 AM, Lisandro Dalcin <dalcinl at gmail.com> wrote:
> 
>> So now we have 9 new, top-level, public matrix types for LMVM... Really?
>> 
>> #define MATLMVM            "lmvm"
>> #define MATLMVMDFP         "lmvmdfp"
>> #define MATLMVMBFGS        "lmvmbfgs"
>> #define MATLMVMSR1         "lmvmsr1"
>> #define MATLMVMBRDN        "lmvmbrdn"
>> #define MATLMVMBADBRDN     "lmvmbadbrdn"
>> #define MATLMVMSYMBRDN     "lmvmsymbrdn"
>> #define MATLMVMSYMBADBRDN  "lmvmsymbadbrdn"
>> #define MATLMVMDIAGBRDN    "lmvmdiagbrdn"
>> 
>> 
>> 
>> 
>> -- 
>> Lisandro Dalcin
>> ============
>> Research Scientist
>> Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
>> Extreme Computing Research Center (ECRC)
>> King Abdullah University of Science and Technology (KAUST)
>> http://ecrc.kaust.edu.sa/
>> 
>> 4700 King Abdullah University of Science and Technology
>> al-Khawarizmi Bldg (Bldg 1), Office # 0109
>> Thuwal 23955-6900, Kingdom of Saudi Arabia
>> http://www.kaust.edu.sa
>> 
>> Office Phone: +966 12 808-0459
> 
> 
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
> 
> https://www.cse.buffalo.edu/~knepley/