In the last post, we showed the connections between chase and techniques developed in databases literature and tree automata literature, and how these connections help us understand equality saturation (EqSat). In this blog post, we will focus on a specific problem EqSat faces: the termination problem1, something my collaborators and I have been working on recently.
While “Goto Considered Harmful” (Dijkstra, 1968) is one of the most famous pieces of writing in Computer Science, its enduring relevance to programming languages is almost wholly unappreciated or — at best — misunderstood. Historically, supporters and detractors from the original letter have addressed themselves to the conclusion that use of the goto statement should be avoided. (Including Knuth [1]) Depressingly, it took over two decades [2] before anyone bothered to empirically test Dijkstra’s claim. To the best of my knowledge, no-one ever disputed, supported, or merely considered Dijkstra’s premises and form of argument.
Hello, and welcome to the first edition of the official UW PLSE blog!
Hi! My name is Matt (he/him), one of the new teaching faculty at the Allen School this fall. I’ve been given a warm welcome by the community at UW, including at PLSE – where I’ve already met some wonderful people who do all things software engineering, programming languages, and running!
The phase-ordering problem is a long standing problem in program optimization: Consider program \((a\times 2)/2\). A program optimizer may readily optimize the subexpression \(a\times 2\) into \(a\ll 1\) and get \((a\ll 1)/2\), at which stage it cannot optimize the program further. Or it can also realize that the multiplication and division operators can be simply canceled out, yielding \(a\). This indicates that applying one optimization may disable another optimization, but naively exploring all optimization orders can lead to a combinatorial explosion.