Calculation of algebraic entropies of d-P_IVand d-P_V

In this paper, we describe the singularity patterns of d-PIV in detail and calculate the algebraic entropies of d-PIV and d-PV, which are shown to be both zeros. However, for the discrete equations that are similar with d-PIV, not all algebraic entropies are zeros. An example shows that even if the equation passes the singularity confinement test, it still has a positive algebraic entropy. We also explore the influence of cyclic patterns and anti-confined patterns in the calculation.