Cunningham's Rule constructions because they tend to average out how many times a variable pivots. It has recently been shown by David Avis and Oliver Friedmann that there is a family of linear programs on which the simplex algorithm equipped with Cunningham's rule requires exponential time. Cunningham's Rule In mathematical optimization, Cunningham's rule (also known as least recently considered rule or round-robin rule) is an algorithmic refinement of the simplex method for linear optimization. The rule was proposed 1979 by W.H. Cunningham to defeat the deformed hypercube constructions by Klee and Minty et. al. (see, e.g. Klee–Minty cube). Cunningham's rule assigns a
Chain rule for short, The derivative function is therefore: Another way of computing this derivative is to view the composite function as the composite of and "h". Applying the chain rule to this situation gives: This is the same as what was computed above. This should be expected because . Sometimes it is necessary to differentiate an arbitrarily long composition of the form formula_23. In this case, define where formula_25 and formula_26 when formula_27. Then the chain rule takes the form or, in the Lagrange notation, The chain rule can be used to derive some well-known differentiation rules. For example, the quotient