1. A computer modeling apparatus, comprising: an input module enabling user specification of inventory information including at least one rundown component, and user specification of refinery product commitments; and a processor routine executable by a computer and coupled to the input module and responsive to the user specification by sequencing refinery operations into a schedule that matches refinery commitments with inventory and unit rundown operations, wherein the refinery operations include refinery operations events, and the processor routine providing on output a display of the schedule in a manner enabling optimized refinery operations.