  We describe the physics and computational power of GRANIITTI Monte Carlo
event generator, a new fully multithreaded engine designed for high energy
diffraction, written in modern C++. The emphasis is especially on the low-mass
domain of central exclusive processes of the S-matrix, where exotic QCD
phenomena such as glueballs are expected and holographic dualities with gravity
may be tested. The generator includes photon-photon, photon-pomeron,
pomeron-pomeron, Durham QCD model and Tensor pomeron model type scattering
amplitudes and advanced spin analysis tools. The generator combines a full
parametric resonance spectrum with continuum interference and forward + central
spin correlations together with event-by-event eikonal screening loop and
forward proton excitation kinematics. We demonstrate the state-of-the-art
capabilities and show how the enigmatic `glueball filter' observable is driven
by spin polarization.
