“…Characteristics of physical systems in equilibrium may change because of variations in temperature, pressure, age, etc. (see Fiacco [5], McCormick [7], Pun [10], Beightler, Phillips, and Wilde [2], Whittle [14], and Bracken and McCormick [3]) while price, income, or technology parameters may induce structural shifts in economic relationships involving, say, consumption or production (see, for instance, Samuelson [11], Takayama [13], Afriat [1], and Silberberg [12]). Also of considerable interest in the context of general nonlinear optimization is a class of programs called "perturbed problems" wherein the capacity levels associated with the structural constraints are treated as parameters in a "perturbed objective function."…”