Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-27 Thread Barry Smith
at-Sea-March-29-Rotterdam.htm > > > From: Barry Smith <bsm...@mcs.anl.gov> > Sent: Saturday, March 25, 2017 1:29 AM > To: Klaij, Christiaan > Cc: Lawrence Mitchell; Matthew Knepley; petsc-users@mcs.anl.gov > Subject: Re: [petsc

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-27 Thread Klaij, Christiaan
-Rotterdam.htm From: Barry Smith <bsm...@mcs.anl.gov> Sent: Saturday, March 25, 2017 1:29 AM To: Klaij, Christiaan Cc: Lawrence Mitchell; Matthew Knepley; petsc-users@mcs.anl.gov Subject: Re: [petsc-users] left and right preconditioning with a constant null space >

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-24 Thread Barry Smith
constant null space. > > Chris > > From: Klaij, Christiaan > Sent: Friday, March 24, 2017 9:05 AM > To: Lawrence Mitchell; Matthew Knepley > Cc: petsc-users@mcs.anl.gov > Subject: Re: [petsc-users] left and right preconditioning w

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-24 Thread Matthew Knepley
On Fri, Mar 24, 2017 at 10:17 AM, Lawrence Mitchell < lawrence.mitch...@imperial.ac.uk> wrote: > > > On 24 Mar 2017, at 15:11, Klaij, Christiaan wrote: > > > > I've written a small PETSc program that loads the four blocks, > > constructs Sp, attaches the null space and solves

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-24 Thread Lawrence Mitchell
> On 24 Mar 2017, at 15:11, Klaij, Christiaan wrote: > > I've written a small PETSc program that loads the four blocks, > constructs Sp, attaches the null space and solves with a random > rhs vector. > > This small program replicates the same behaviour as the real > code:

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-24 Thread Klaij, Christiaan
24, 2017 1:34 PM To: Lawrence Mitchell; Matthew Knepley Cc: petsc-users@mcs.anl.gov Subject: Re: [petsc-users] left and right preconditioning with a constant null space I've also loaded the four blocks into matlab, computed Sp = A11 - A10 inv(diag(A00)) A01 and confirmed that Sp has indeed a

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-24 Thread Klaij, Christiaan
From: Lawrence Mitchell <lawrence.mitch...@imperial.ac.uk> Sent: Thursday, March 23, 2017 4:52 PM To: Klaij, Christiaan; Matthew Knepley Cc: petsc-users@mcs.anl.gov Subject: Re: [petsc-users] left and right preconditioning with a constant null space On 23/03/17 15:37, Klaij, Christiaan wrote: > Ye

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-23 Thread Lawrence Mitchell
On 23/03/17 15:37, Klaij, Christiaan wrote: > Yes, that's clearer, thanks! I do have is0 and is1 so I can try > PetscObjectCompose and let you know. > > Note though that the viewer reports that both S and A11 have a > null space attached... My matrix is a matnest and I've attached a > null

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-23 Thread Klaij, Christiaan
list-Human-Performance.htm From: Lawrence Mitchell <lawrence.mitch...@imperial.ac.uk> Sent: Thursday, March 23, 2017 11:57 AM To: Klaij, Christiaan; Matthew Knepley Cc: petsc-users@mcs.anl.gov Subject: Re: [petsc-users] left and right preco

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-23 Thread Lawrence Mitchell
On 23/03/17 08:42, Klaij, Christiaan wrote: > Matt, Lawrence > > > The same problem happens when using gmres with rtol 1e-6 in the > schur complement (attachment "left_schur"). I'm not sure what > this tells us. If I understand Lawrence correctly, the null space > may be attached to the wrong

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-22 Thread Lawrence Mitchell
> On 22 Mar 2017, at 16:39, Matthew Knepley wrote: > > Hmm, I wonder if the problem is that A11 has the nullspace, but the PC pmat > is actually B^T diag(A)^{-1} B. I have > to look where the solver is actually taking the nullspace from. We need to > improve the -ksp_view

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-22 Thread Matthew Knepley
htm> > > -- > *From:* Matthew Knepley <knep...@gmail.com> > *Sent:* Wednesday, March 22, 2017 4:47 PM > *To:* Klaij, Christiaan > *Cc:* petsc-users@mcs.anl.gov > *Subject:* Re: [petsc-users] left and right preconditioning with a >

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-22 Thread Klaij, Christiaan
nghai for the first time, March 28<http://www.marin.nl/web/News/News-items/Software-seminar-in-Shanghai-for-the-first-time-March-28.htm> From: Matthew Knepley <knep...@gmail.com> Sent: Wednesday, March 22, 2017 4:47 PM To: Klaij, Christiaan Cc: petsc-users@m

Re: [petsc-users] left and right preconditioning with a constant null space

2017-03-22 Thread Matthew Knepley
On Wed, Mar 22, 2017 at 2:58 PM, Klaij, Christiaan wrote: > I'm solving the Navier-Stokes equations using PCFieldSplit type > Schur and Selfp. This particular case has only Neumann conditions > for the pressure field. > > With left preconditioning and no nullspace, I see that

[petsc-users] left and right preconditioning with a constant null space

2017-03-22 Thread Klaij, Christiaan
I'm solving the Navier-Stokes equations using PCFieldSplit type Schur and Selfp. This particular case has only Neumann conditions for the pressure field. With left preconditioning and no nullspace, I see that the KSP solver for S does not converge (attachment "left_nonullsp") in either norm.