Methods and systems for process rollback in a shared memory parallel processor computing environment use priority values to control process rollback. The polymerization catalyst is a metallocene, and the melting or softening point of the polyolefin made using the catalyst is at least 20\xb0 C. The ride plate includes a base fixable to the boat body. Pixels in the source video image are replicated to form a partially up-scaled video image that has frequency content well below the Nyquist rate of the image. The level of criticality may be based on an estimated time period remaining until the flow assurance curve and the operating curve will intersect.