  We have developed a Monte Carlo event generator for non-resonant diphoton
($\gamma\gamma$) production at hadron collisions in the framework of GR@PPA,
which consistently includes additional one-jet production. The jet-matching
method developed for initial-state jet production has been extended to the
final state in order to regularize the final-state QED divergence in the $qg
\rightarrow \gamma\gamma + q$ process. A QCD/QED-mixed parton shower (PS) has
been developed to complete the matching. The PS has the capability of enforcing
hard-photon radiation, and small-$Q^{2}$ photon radiations that are not covered
by the PS are supplemented by using a fragmentation function. The generated
events can be passed to general-purpose event generators in order to perform
the simulations down to the hadron level. Thus, we can simulate the isolation
requirements that must be applied in experiments at the hadron level. The
simulation results are in reasonable agreement with the predictions from RESBOS
and DIPHOX. The simulated hadron-level events can be further fed to detector
simulations in order to investigate the detailed performance of experiments.
