"Annotating pure code for parallelism" docs based on old par/pseq primitives
The example code in GHC 7.10.2 docs "7.28. Concurrent and Parallel Haskell", then in "7.15.4. Annotating pure code for parallelism" the recommendation is to use par and pseq. These primitives pre-dates the strategy combinators rpar and rseq. The example given is:
import Control.Parallel
nfib :: Int -> Int
nfib n | n <= 1 = 1
| otherwise = par n1 (seq n2 (n1 + n2 + 1))
where n1 = nfib (n-1)
n2 = nfib (n-2)The paper "Seq no more: Better Strategies for Parallel Haskell" (http://www.macs.hw.ac.uk/~hwloidl/publications/strategies10.pdf) advocates Eval as an "evaluation order" monad, as preferable (versus par and seq) for loose control of evaluation order of parallelism. Moreover, Simon Marlow's "Parallel and Concurrent Programming in Haskell" doesn't mention the par and seq primitives at all.
Should the GHC docs for "Concurrent and Parallel Haskell" encourage the use Eval combinators, either in addition to or instead of the par and seq primitives? I'd be happy to contribute an update to the docs if people agree to a shift in emphasis towards the Eval monad in the docs.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.10.2 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | lowest |
| Resolution | Unresolved |
| Component | Documentation |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | simonmar |
| Operating system | |
| Architecture |