On Hoffman's celebrated cycling LP example ?
We answer two questions that naturally arise while dealing with Hoffman's celebrated 50-year-old linear program to be solved by the primal simplex method, where an angle ? ? and a scaling factor ? ? are adjustable parameters. In particular, we determine what conditions have to be imposed on ? ? for classical cycling to occur with ?=2?/5 ? = 2 ? / 5 , and what on ? ? with ?=tan(?) ? =  tan ( ? ) . The first answer reveals that the sufficient condition widely spread over the literature is false, so fixing it turns this example into a correct example of classical cycling. Some progress towards necessary and sufficient conditions for cycling to occur in this example is also reported.
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