  We introduce an efficient cellular automaton for the coagulation-fission
process with diffusion 2A->3A, 2A->A in arbitrary dimensions. As the well-known
Domany-Kinzel model, it is defined on a tilted hypercubic lattice and evolves
by parallel updates. The model exhibits a non-equilibrium phase transition from
an active into an absorbing phase and its critical properties are expected to
be of the same type as in the pair contact process with diffusion.
High-precision simulations on a parallel computer suggest that various
quantities of interest do not show the expected power-law scaling, calling for
new approaches to understand this unusual type of critical behavior.
