[Haskell-cafe] NDP documentation

Andrew Coppin andrewcoppin at btinternet.com
Wed Jul 25 14:47:33 EDT 2007

Bulat Ziganshin wrote:
> Hello Andrew,
> Monday, July 23, 2007, 11:50:32 PM, you wrote:
>> Actually, I was just reading through all the Data Parallel Haskell and
>> Nested Data Parallelism documentation. It says in several places that 
>> "parallel array comprehensions are available since GHC 6.6, but they are
>> broken; please use the development versions; this will be fixed in GHC
>> 6.6.1".
> parallel arrays (GHC.PArr) was implemented at least in ghc 6.4 and my
> program using it was worked fine with 6.4.*, 6.6 and 6.6.1 now. but i
> don't use comprehensions, only !: operator

To my utter frustration, Thunderbird is once again refusing to download 
the message I actually want to reply to, but anyway...

Acording to the wiki, the parallel array stuff has two halves. First, 
there's the parallel array library that does all the good stuff, and 
then there's a seperate library that gives you all the nice syntax 
sugar. (I.e., parallel array comprehensions.) Automatic transformation 
from one to the other is not yet implemented. So at the moment, you can 
try out the neat new syntax - but it won't actually run in parallel - or 
you can play with the low-level stuff.

The wiki also says that the parallel array comprehensions are "buggy" in 
GHC 6.6, and you should use HEAD until GHC 6.6.1 comes out. Well, 6.6.1 
*is* out now, so I'm wondering if somebody should change the information 
on the wiki?

Also, while I'm here... Why hasn't the automatic conversion been done 
yet? Is it because nobody has had time, or is it because there's an 
actual "problem"?

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