Run-time reduction is achieved in timing performance of a logical design,
such as a digital integrated circuit. A portion of the logical design
that is expected to be stable with respect to timing performance, such as
a clock tree, is identified. Timing sensitivities, including
sensitivities to sources of variability, of the identified portion of the
logical design are determined at a given instant. The timing
sensitivities of the identified portion of the logical design are saved
for re-use. The saved timing sensitivities are re-used throughout the
timing analysis and in subsequent timing analyses.