[petsc-users] KSPComputeRitz, GMRES, matrix with complex number

[feng wang]

Hi Mark,

Thanks for your reply!

Maybe I have a misunderstanding of the documentation of KSPComputeRitz (https://petsc.org/main/docs/manualpages/KSP/KSPComputeRitz/).  It says "-this is currently not implemented when PETSc is built with complex numbers".

But if it works, I will give it a try.

Thanks,
Feng


<https://petsc.org/main/docs/manualpages/KSP/KSPComputeRitz/>

________________________________
From: Mark Adams <mfadams at lbl.gov>
Sent: 14 July 2022 12:23
To: feng wang <snailsoar at hotmail.com>
Cc: petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] KSPComputeRitz, GMRES, matrix with complex number

Why do you say it only works with Real? You need to configure PETSc to use complex numbers and it should work.
This is an advanced method and it does not have any tests, which basically says it is very experimental.
Don't expect it to be very robust.

Mark

On Thu, Jul 14, 2022 at 7:19 AM feng wang <snailsoar at hotmail.com<mailto:snailsoar at hotmail.com>> wrote:
Dear All,

I am using GMRES with complex numbers and would like to compute the Ritz values. I am looking at KSPComputeRitz<https://petsc.org/main/docs/manualpages/KSP/KSPComputeRitz/>  and it seems to me that it only works with Petsc compiled with real numbers. Is there an easy alternative way to compute Ritz values for matrices with complex numbers?

Thanks,
Feng
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