  Within the framework of the improved isospin dependent quantum molecular
dynamics (ImIQMD) model, the dynamics of pion emission in heavy-ion collisions
in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation
densities is investigated systematically. The total pion multiplicities and the
$\pi^{-}/\pi^{+}$ yields are calculated for selected Skyrme parameters SkP,
SLy6, Ska and SIII, and also for the cases of different stiffness of symmetry
energy with the parameter SLy6. The influence of Coulomb potential, symmetry
energy and in-medium pion potential on the pion production is investigated and
compared each other by analyzing the distributions of transverse momentum and
longitudinal rapidity and also the excitation functions of the total pion and
the $\pi^{-}/\pi^{+}$ ratio. The directed flow, elliptic flow and polar angle
distributions are calculated at the cases of different collision centralities
and symmetry energies.
