Program Derivation is the practice of beginning with a specification of a function, and by a series of mechanical steps, deriving an efficient implementation. In the “Algebra of Programming” approach, pioneered by Richard Bird, Oege de Moor, and Lambert Merteens, we can derive efficient functional programs by a series of algebraic manipulations, much schoolchildren can take a typical algebraic function, “solve for x” and then simplify. In the early-mid 90s, this school of research turned its attention to the problem of parallel computing and developed many of the foundations for what is now called MapReduce. This workshop will run through some famous and nifty algorithms and derivations, parallel and sequential alike. Attendees should walk away with a few weird tricks to level up their equational reasoning in everyday programming contexts, and hopefully enough intuition to dive more deeply into this rich body of literature.