Chapter 18: Reversible Computing
Peter M. Kogge · Society for Industrial and Applied Mathematics eBooks · 2022
The discussion of virtually all the computing models in this book focuses on what kinds of problems they can compute and how fast they can compute them. In the modern world, how much energy it takes to do the computations is also of critical importance, particularly as we build both bigger and bigger systems to attack very large problems and smaller and smaller systems where battery life is paramount. Thus serious questions can be raised as to “are there computational alternatives to our current models that are inherently more energy efficient?” and “are they as computationally rich as the von Neumann model?” Paradoxically, one answer lies in models where computations can be “undone.” Such discussions started back in the 1960s when Rolf Landauer [131] laid the foundation for a theory of energy complexity in computation by integrating the concept of entropy from thermodynamics with entropy in information theory. Irreversibility was tied directly to unavoidable energy loss, so the only way to avoid such loss is by having computing systems that are not “irreversible.”