download example : LapEigenvalues1D.edp
int np=40; mesh Th = square(np,1,[x,y/50]); //transformation for visualization comfort… plot(Th,wait=1,aspectratio=1); fespace Vh(Th,P1); Vh u,v; func f=1.; varf Laplace1d(u,v) = int1d(Th,1)(dx(u)*dx(v))+on(2,3,4,u=0); varf RHS(u,v) = int1d(Th,1)(u*v);//+on(2,3,4,u=0); matrix A,B; A = Laplace1d(Vh,Vh); B = RHS(Vh,Vh); int nev=20; real sigma= 0; real[int] ev(nev); // to store nev eigein value Vh[int] eV(nev); // to store nev eigen vector int k=EigenValue(A,B,sym=false,sigma=sigma,value=ev,vector=eV,tol=1e-10,maxit=0,ncv=0);