Sperner's lemma and robust machines

Abstract.

Sperner's lemma states that any admissible coloring of any triangulation of the unit triangle has a 3‐colored triangle. In this paper, we first show that any algorithm to find this 3‐colored triangle that treats the coloring itself as an oracle must be in the worst case linear in the size of the triangulation. Successively, we apply this lower bound to solve three open questions on robust machines posed by Hartmanis and Hemachandra.