Re: [petsc-users] Very small right hand side and KSP_DIVERGED_DTOL

> On Mar 24, 2017, at 8:56 AM, alexandre this wrote: > > Dear all, > > I'm in the configuration where I need to solve a linear system Ax = b where b > is very small although not equal to zero. > > It appears that, in this configuration, the initial residual of the

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

> On Mar 24, 2017, at 10:11 AM, 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] Very small right hand side and KSP_DIVERGED_DTOL

On Fri, Mar 24, 2017 at 8:56 AM, alexandre this wrote: > Dear all, > > I'm in the configuration where I need to solve a linear system Ax = b > where b is very small although not equal to zero. > > It appears that, in this configuration, the initial residual of the first

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

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

> 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

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: convergence in the preconditioned norm, stagnation in the unpreconditioned norm. But when

[petsc-users] Very small right hand side and KSP_DIVERGED_DTOL

Dear all, I'm in the configuration where I need to solve a linear system Ax = b where b is very small although not equal to zero. It appears that, in this configuration, the initial residual of the first iteration of the solver is completely out of reach and the KSP_DIVERGED_DTOL is raised. In

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 constant null space. Chris dr. ir. Christiaan Klaij | Senior Researcher | Research & Development MARIN | T +31 317 49 33 44 | mailto:c.kl...@marin.nl |