Quanta Magazine


Leslie Lamport may not be a household name, but he’s behind a few of them for computer scientists: the typesetting program LaTeX and the work that made cloud infrastructure at Google and Amazon possible. He’s also brought more attention to a handful of problems, giving them distinctive names like the bakery algorithm and the Byzantine Generals Problem. This is no accident. The 81-year-old computer scientist is unusually thoughtful about how people use and think about software.

In 2013, he won the A.M. Turing Award, considered the Nobel Prize of computing, for his work on distributed systems, where multiple components on different networks coordinate to achieve a common objective. Internet searches, cloud computing and artificial intelligence all involve orchestrating legions of powerful computing machines to work together. Of course, this kind of coordination opens you up to more problems.

“A distributed system is one in which the failure of a computer you didn’t even know existed can render your own computer unusable,” Lamport once said.

Among the biggest sources of problems are “concurrent systems,” where multiple computing operations happen during overlapping slices of time, leading to ambiguity: Which computer’s clock is the right one? In a seminal 1978 paper, Lamport introduced the notion of “causality” to solve this issue, using an insight from special relativity. Two observers may disagree on the order of events, but if one event causes another, that eliminates the ambiguity. And sending or receiving a message can establish causality among multiple processes. Logical clocks — now also called Lamport clocks — provided a standard way to reason about concurrent systems.

With this tool in hand, computer scientists next wondered how they could systematically make these connected computers even bigger, without adding bugs. Lamport came up with an elegant solution: Paxos, a “consensus algorithm” that allows multiple computers to execute complex tasks. Without Paxos and its family of algorithms, modern computing could not exist.