I would like to know if it is possible to replace the small values, for example lower than 1e-14, with zero? I am having spurious eigenvalues due to that small numbers.

I assemble the matrix as given below,

```
F = derivative(Pi_ext, w, w_test)
J = derivative(F_ext, w, w_trial)
asm = SystemAssembler(J, F, bcs)
M = PETScMatrix()
asm.assemble(M)
```

Thanks…