Flexible GMRES (fgmres)

I’m utilizing fGMRES and require guidance on how to implement the restart number.

-ksp_gmres_restart XYZ?

Would you kindly provide me with examples relevant to my case, such as the Navier-Stokes or Stokes equations using “-ksp_gmres_restart”? Additionally, I’m currently working with splitting the solution of the linear system into three variables (u, ksi, p) in order to calculate erroru, errorksi, and errorp. I need to use the fieldsplit preconditioner to split the linear system. If possible, please provide examples if you have it to support my case. Thank you.

There are many examples in https://github.com/FreeFem/FreeFem-sources/tree/master/examples/hpddm.