vectorisation code?

[Simon Peyton Jones]

Austin, (or anyone else)

Manuel says:

|  > Would it be ok if we left it in the repo, but CPP'd it out so that
|  we
|  > didn't compile everything?  (The DPH library is in the same state at
|  > the moment.)
|  >
|  > It might suffer bit-rot, but it’d still be there for resurrection.
|  
|  Sure, that’s ok.

Could you action this?  Just avoid compiling anything in 'vectorise/', using (I suppose) cpp to create a stub where necessary.

Leave enough comments to explain!

Simon

|  
|  I hope everything is fine in Cambridge!
|  Manuel
|  
|  > |  -----Original Message-----
|  > |  From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of
|  > | Manuel M T Chakravarty
|  > |  Sent: 16 January 2015 02:58
|  > |  To: Richard Eisenberg
|  > |  Cc: ghc-devs at haskell.org Devs
|  > |  Subject: Re: vectorisation code?
|  > |
|  > |  [Sorry, sent from the wrong account at first.]
|  > |
|  > |  We currently don’t have the resources to work on DPH. I would
|  > | obviously prefer to leave the code in, in the hope that we will be
|  > | able to return to it.
|  > |
|  > |  Manuel
|  > |
|  > |  > Richard Eisenberg <eir at cis.upenn.edu>:
|  > |  >
|  > |  > Hi devs,
|  > |  >
|  > |  > There's a sizable number of modules in the `vectorise`
|  > | subdirectory  of GHC. I'm sure these do all sorts of wonderful
|  > | things. But what,  exactly? And, does anyone make use of these
|  wonderful things?
|  > |  >
|  > |  > A quick poking through the code shows a tiny link between the
|  > | vectorise code and the rest of GHC -- the function `vectorise`
|  > | exported from the module `Vectorise`, which is named in exactly
|  one
|  > | place from SimplCore. From what I can tell, the function will be
|  > | called only when `-fvectorise` is specified, and then it seems to
|  > | interact with a {-# VECTORISE #-} pragma. However, `{-# VECTORISE
|  > | #-}`  doesn't appear in the manual at all, and `-fvectorise` is
|  > | given only a  cursory explanation. It seems these work with DPH...
|  > | which has been  disabled, no? Searching online finds several hits,
|  > | but nothing more  recent than 2012.
|  > |  >
|  > |  > I hope this question doesn't offend -- it seems that
|  > | vectorisation  probably has amazing performance gains. Yet, the
|  > | feature also seems  unloved. In the meantime, compiling (and
|  > | recompiling, and
|  > |  recompiling...) the modules takes time, as does going through
|  them
|  > | to  propagate changes from elsewhere. If this feature is truly
|  > | orphaned,  unloved, and unused at the moment, is it reasonable to
|  > | consider  putting it on furlough?
|  > |  >
|  > |  > Thanks,
|  > |  > Richard
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