Cohen

CSP instances are commonly solved by backtracking search combined with constraint propagation. During search, constraint solvers aim to remove any literals (variable-value pair) that can be shown not to be part of any solution. This literal removal, called propagation, is the beating heart of modern constraint solvers. A significant proportion of the runtime of propagating constraint solvers is spent running propagation algorithms. Therefore any mechanism for reducing how frequently propagators are called leads directly to significant performance improvements.