  We consider a 3-dimensional (3D) non-Hermitian exceptional line semimetal
model and take open boundary conditions in x, y, and z directions separately.
In each case, we calculate the parameter regions where the bulk-boundary
correspondence is broken. The breakdown of the bulk-boundary correspondence is
manifested by the deviation from unit circles of generalized Brillouin zones
(GBZ) and the discrepancy between spectra calculated with open boundary
conditions (OBC) and periodic boundary conditions (PBC). The consistency
between OBC and PBC spectra can be recovered if the PBC spectra are calculated
with GBZs. We use both unit-circle Brillouin zones (BZ) and GBZs to plot the
topological phase diagrams. The systematic analysis of the differences between
the two phase diagrams suggests that it is necessary to use GBZ to characterize
the bulk-boundary correspondence of non-Hermitian models.
