This reminds me of the Chapel programming language (http://chapel.cray.com/), which seeks to be a relatively high-level language for all parallel computation.

They differ in that Harlan is just for GPUs, while Chapel aims to be good for all parallel computation. Also, Harlan uses Lisp syntax, while Chapel's syntax is C-based.

Any comments on similarities/differences between them from those who know either one better than I?