  We evaluated the topological charge density of SU(3) gauge fields on lattice
by calculating the trace of overlap Dirac matrix employing symmetric
multi-probing(SMP) method with 3 modes. Since the topological charge $Q$ for a
given lattice configuration must be an integer number, it's easy to estimate
the systematic error (the deviation of $Q$ to nearest integer). The results
showed high efficiency and accuracy in calculating the trace of the inverse of
a large sparse matrix with locality by using SMP sources, compared with that
using point sources. We also showed the correlation between the errors and
probing scheme parameter $r_{\mathrm{min}}$ as well as lattice volume $N_{L}$
and lattice spacing $a$. It was found that the computing time of calculating
the trace by employing SMP sources is less dependent on $N_{L}$ than that by
using point sources. Therefore the SMP method is very suitable for calculations
on large lattices.
