[Nek5000-users] Interfacing with Arpack

[nek5000-users at lists.mcs.anl.gov]

Dear users and developers,
I would like to solve a generalized eigenvalue problem with Arpack, 
based on Nek subroutines. Using reverse communication interface, I only 
need to express the action of the matrices on the vectors, but I am not 
sure on how to apply the mass matrix and the inverse mass matrix in the 
Pn-Pn formulation.
Is it sufficient to write:
call col2(p1,bm1,n)      !apply mass matrix to vector p1
...
call invcol2(p1,bm1,n)  ! apply inverse mass matrix to vector p1
or should I do:
call rzero(h1,n)
call rone(h2,n)
call hmholtz('vel',p,p1,h1,h2,pmask,vmult,imsh,tolh,maxiter,isd)
to apply inverse mass matrix to p1, or should I do something else?
Also, from a related question from a couple of years ago, should I call 
col2(v,vmask,n) after each matrix-vector product?
Thank you in advance.
Best,
Giuseppe