An internal combustion engine having combustion cylinders capable of
running on gasoline in either a spark ignition mode or in a homogenous
charge compression mode. The allocation of cylinders in each mode is
dynamic and may be dynamically controlled and varied during operating of
the engine. Also, the engine may include plural aftertreatment systems
which may be dynamically selected, typically based on the combustion
mode(s) in which the cylinders are operating.