Thank you Barry for your comments, So if you're ok with this, I'll work on it and I'll propose you a contribution later.
Sylvain 2014-08-25 20:02 GMT+02:00 Barry Smith <[email protected]>: > > On Aug 25, 2014, at 9:59 AM, Sylvain Mercier <[email protected]> > wrote: > > > Thank you Matthew and Hong. > > > > That's too bad... > > I was wondering if it would be possible to add this alternative only in > the MUMPS interface. > > Indeed, in the field of solid mechanics (where 3D, beams and shell are > often mixed thanks to Lagrange multipliers), it's very usefull to factorize > a matrix in single precision thanks to MUMPS, and use it to precondition a > sequence of systems solved in double precision. It turns to be very robust > and quite fast. > > > > In src/mat/impls/aij/mpi/mumps/mumps.c, a new type, say > PetscMumpsSingleScalar, could be defined in order to pass the required > information to the single precision > > MUMPS solver. > > > > Would the Petsc team accept to integrate such a feature? > > Sylvain, > > Yes this would be possible; it is the maintenance and clarity of the > code that becomes an issue. Basically all the MatConvertToTriples() > routines would need to optionally make a copy of the numerical values into > single precision and similarly the right hand side would need to do the > same when some option on the factorization saying to use single precision > is set. > > Barry > > > > > > > Thanks, > > Sylvain > > > > > > 2014-08-20 17:57 GMT+02:00 Matthew Knepley <[email protected]>: > > On Wed, Aug 20, 2014 at 7:53 AM, Sylvain Mercier < > [email protected]> wrote: > > Hi everyone, > > > > I'm using PETSc to solve saddle point systems. I have found a block > preconditionner which requires to solve a smaller symmetric positive > definite system. I do it with MUMPS which is fast an robust. > > However, I would like to use this solver in single precision in order to > compare the performances. > > > > So is it possible to use MUMPS in single precision inside a double > precision solving with PETSc? > > > > No, right now PETSc must have all the same precision. We have > investigated several methods for > > using multi-precision, but none has satisfied all our needs. > > > > Thanks, > > > > Matt > > > > Thanks, > > Sylvain > > > > > > > > -- > > 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 > > > >
