Hello dear Julia Users,
In order to calculate eigenvalues and vectors I am currently using the package IterativeSolvers, but I often get the error that my input matrices are not positive definite. My code is like this:
result = lobpcg(K, G, false, nte1 ; maxiter = 200)
where K is the stiffness matrix of a mesh and G the mass matrix. So from a mathematical point of view the matrices have to be positive definite. Somehow the function lobpcg() disagrees and throws an error. Before IterativeSolvers, I used the function eigs() from the package Arpack and I never had any issue of that kind. My matrix implementations are correct, since I compared my results of eigs() to commercial solvers. Does anybody know, how I can solve this?