Dear forum,

I am using FreeFEM++ v4.8 for Windows to perform a stability analysis with the SLEPc library. If I set -np 1 and I repeat the simulations without changing anything else I get everytime the same results. When I change -np 2 and I repeat the simulations without changing anything else I get different results and I don’t understand why. I attach the code without the equations:

mesh Th=…

fespace XXXXXFES(Th,[P1,P1,P1,P1]);

XXXXXFES[u,v,w,p];

XXXXXFES[ue,ve,we,pe];

XXXXXFES[hy,hx,hz,q];

func E = [P1, P1, P1, P1];

varf LNSE ([ue,ve,we,pe],[hy,hx,hz,q])

=int2d(Th)…

varf b([ue,ve,we,pe],[hy,hx,hz,q])

=int2d(Th)…

Mat M;

macro def(j) [j, j#A, j#B, j#C]

macro init(j) [j, j, j, j]

createMat(Th, M, E);

M = LNSE(XXXXXFES, XXXXXFES);

matrix B = b(XXXXXFES, XXXXXFES);

Mat J(M, B);

int nev = 100;

int ncv = 2*nev;

real tol = 1e-12;

complex[int] EigenVal(nev);

XXXXXFES[int] [EigenVecu,EigenVecv,EigenVecw,EigenVecp] (nev);

complex Shift = getARGV("-shift_real", 0) + getARGV("-shift_imag", 10) * 1i; /

string EVSParam =

“-eps_tol " + tol +” "+

“-eps_nev " + nev +” "+

"-eps_type krylovschur " +

"-st_type sinvert " +

"-eps_monitor_conv " +

"-eps_target " + real(Shift) + “+” + imag(Shift) + “i”;

int i, k;

k = EPSSolve(M, J, values=EigenVal, vectors=EigenVecu, sparams = EVSParam);

Did someone encounter this problem before?

Regards,

Robert