[petsc-users] PetscOptionsSetValue syntax

[Pierre Jolivet]

> On 18 Nov 2022, at 2:47 PM, Karthikeyan Chockalingam - STFC UKRI <karthikeyan.chockalingam at stfc.ac.uk> wrote:
> 
> 
> Thank you. I added
>  
>     ierr = KSPSetFromOptions(ksp); CHKERRQ(ierr);
>  
> before PetscOptionsSetValue but still I don’t see the ksp iterations or any other info flags I set.
> I am not passing anything via the command line and believe PetscOptionsSetValue would set the flags.

If you call KSPSetFromOptions() before you set any options, there is nothing to set.
Usually, you want to delay calling that function up until you are done setting options.

Thanks,
Pierre

> Best,
> Karthik.
>  
>  
> From: Pierre Jolivet <pierre at joliv.et>
> Date: Friday, 18 November 2022 at 13:36
> To: Chockalingam, Karthikeyan (STFC,DL,HC) <karthikeyan.chockalingam at stfc.ac.uk>
> Cc: petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>
> Subject: Re: [petsc-users] PetscOptionsSetValue syntax
> 
>  
> 
> 
> On 18 Nov 2022, at 2:32 PM, Karthikeyan Chockalingam - STFC UKRI via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> 
> Hello,
>  
> I would like to move from code to using options.
>  
>    KSP           ksp;
>     PC            pc;
>     KSPCreate(PETSC_COMM_WORLD, &ksp);
>     KSPSetOperators(ksp, A, A);
>  
> I tried using PetscOptionsSetValue as below
>  
>     ierr = PetscOptionsSetValue(NULL,"-ksp_type", "cg"); CHKERRQ(ierr);
>     ierr = PetscOptionsSetValue(NULL,"-pc_type", "jacobi"); CHKERRQ(ierr);
>     ierr = PetscOptionsSetValue(NULL, "-ksp_monitor", NULL);CHKERRQ(ierr);
>     ierr = PetscOptionsSetValue(NULL, "-ksp_view", NULL);CHKERRQ(ierr);
>     ierr = PetscOptionsSetValue(NULL, "-ksp_monitor_true_residual", NULL);CHKERRQ(ierr);
>     ierr = PetscOptionsSetValue(NULL, "-ksp_converged_reason", NULL);CHKERRQ(ierr);
>  
>     KSPSolve(ksp, b, x);
>  
> But I believe none of the string flags where picked up by PETSc. What am I missing?
>  
> KSPSetFromOptions()
>  
> Thanks,
> Pierre
> 
> 
> Thank you for your help.
>  
> Kind regards,
> Karthik.
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