This lecture is about a programming model for deterministic parallelism, introduced by Simon Marlow and colleagues. It introduces the Par Monad, a monad for deterministic parallelism, and shows how I-structures are used to exchange information between parallel tasks (or "blobs"), see Marlow's Haskell'11 (Links to an external site.) paper with Ryan Newton and Simon PJ. You should read this paper.

Take a look at the I-Structures paper referred to in the lecture (not obligatory but interesting). See PCPH chapter 4.

Also, Phil Wadler's "Essence of Functional Programming" is a very interesting read, and it covers monads and continuation passing style.

The Par monad is based on Koen Claessen's Poor Man's Concurrency Monad (we call it PMC, see his JFP Pearl).

Before getting on to the Par monad, we take a look at Petricek's use of monad comprehensions and parallel list comprehensions combined with the Eval monad (see Petricek's paper, which I advise you to read). That paper can also help with understanding PMC.

Slides:

Koen's slides about PMC (for info)

Lecture423.pdf

robertsupdatedslides.pdf

Uncommented Haskell code for playing with the Poor Man's Concurrency Monad L3.hs

Comment from Mary: The Par monad provides quite an attractive approach to deterministic parallel programming in Haskell. However, the question of what set of combinators should go on top of this to ease the job of the programmer has not been addressed as much as I expected when we started this course. The github version contains a file of combinators but it is very much work in progress. If you find yourself with time on your hands, you might want to think about and implement some combinators. For instance, it would be nice to have combinators that express both how to break up input data and how to control task granularity. There is clearly more research to be done!

The version of the Par monad that Max Algehed (a former student and then TA) has made that allows you to draw pictures of your programs is at

VisPar