[petsc-users] Generalized eigenvalue problem using quad precision

[Jose E. Roman]

Have you tried with inexact shift-and-invert, i.e. with an iterative KSP instead of MUMPS? Or with preconditioned eigensolvers (GD or JD)?

If you want, send the matrix to my personal address and I will try a few things.

Jose



> El 5 mar 2018, a las 19:50, Santiago Andres Triana <repepo at gmail.com> escribió:
> 
> Dear Jose,
> 
> Thanks for your reply. The problem I deal with (rotational fluid dynamics) involves a very small parameter, the Ekman number, which needs to be as small as possible, hopefully 10^-10 or smaller (typical of the molten core of a planet). I have noticed (and other authors before) that round-off errors become more noticeable as this Ekman number is made smaller. That is why it would be nice to have some calculations done with quad precision, it will also help to estimate the round-off errors when working with double-precision.
> 
> As far as I understand MUMPS doesn't do quad precision but all native methods in petsc/slepc can do it.
> 
> Below is the output of -eps_view for a typical run. Thanks again!
> 
> Santiago
>