Re: default roles
Hi, On Tue, Oct 8, 2013 at 3:21 AM, Richard Eisenberg e...@cis.upenn.edu wrote: We considered this for a while, but it led to a strange design -- to do it right, you would have to import all constructors for all datatypes *recursively* out to the leaves, starting at the datatypes mentioned in the class for which you wanted to use GND. This would mean potentially a whole lot of imports for symbols not actually used in the text of a program. I'm not sure I understand why constructors are involved in this. Wouldn't something like the following potentially be useful? data Role = Nominal | Representational | Phantom | Fun Role Role type family HasRole (t :: k) :: Role data MyData a b = MyData a data MyGADT a b where MyGADT :: MyGADT a Int type instance HasRole MyData = Fun Representational Phantom type instance HasRole MyGADT = Fun Representational Nominal type instance HasRole Traversable = Nominal HasRole instances would be automatically given by GHC. Cheers, Pedro ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: ghc src snapshots
I built http://petersen.fedorapeople.org/ghc/ghc-7.7.20131005-src.tar.bz2http://petersen.fedorapeople.org/ghc/ for Fedora (http://koji.fedoraproject.org/koji/taskinfo?taskID=6034005) and uploaded the builds for x86_64, i686 and armv7hl to my fedorapeople repo: http://repos.fedorapeople.org/repos/petersen/ghc-7.7 Initial basic testing suggests it works okay, but let me know if you notice any Fedora specific problems. Jens ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: default roles
Pedro is suggesting a way for a Haskell type-level program to gain access to
role information. This might indeed be useful, but it doesn't seem terribly
related to the problem of defaults / abstraction. The problem has to do with
definitions like these:
module A where
data S a b = S1 a | S2 b
data T a b = MkT (S a b)
module B where
import A ( {- what goes here? -} )
class C a where
mkT :: T Bool a
instance C Int where ...
newtype Age = MkAge Int deriving C
What constructors do we need in order to convert the (C Int) instance to (C
Age) by hand? To me, it looks like we need MkT and S2, but not S1. Yet, this is
not obvious and seems to be quite confusing.
I hope this helps understanding the issue!
Richard
On Oct 8, 2013, at 4:01 AM, José Pedro Magalhães drei...@gmail.com wrote:
Hi,
On Tue, Oct 8, 2013 at 3:21 AM, Richard Eisenberg e...@cis.upenn.edu wrote:
We considered this for a while, but it led to a strange design -- to do it
right, you would have to import all constructors for all datatypes
*recursively* out to the leaves, starting at the datatypes mentioned in the
class for which you wanted to use GND. This would mean potentially a whole
lot of imports for symbols not actually used in the text of a program.
I'm not sure I understand why constructors are involved in this. Wouldn't
something like
the following potentially be useful?
data Role = Nominal | Representational | Phantom | Fun Role Role
type family HasRole (t :: k) :: Role
data MyData a b = MyData a
data MyGADT a b where MyGADT :: MyGADT a Int
type instance HasRole MyData = Fun Representational Phantom
type instance HasRole MyGADT = Fun Representational Nominal
type instance HasRole Traversable = Nominal
HasRole instances would be automatically given by GHC.
Cheers,
Pedro
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Re: default roles
I don't understand it either. Type family solution, however, seems wrong. See, if we, somehow, make something nominal when it has to be representational — well, some code won't compile, but nothing really bad happens. If, on the other hand, we by some miracle make something representational when in should be nominal — we can get a runtime error. It seems to be very similar to how type classes work, with nominal being the default, and representational a type class. Consider, for example, the Tricky example from the slides, slightly changed: data Tricky2 a b c = MkTricky2 (a c) (b c) Currently parameter c would be nominal. I suggest that it should be representational if and only if it's representational for BOTH a and b. WIth type classes it would be very simple: instance (HasRepresentationalParameter a, HasRepresentationalParameter b) = HasRepresentationalParameter (Tricky2 a b) With type families... well, apparently I don't have enough milliolegs to figure out how to do it. On Tue, Oct 8, 2013 at 12:01 PM, José Pedro Magalhães drei...@gmail.comwrote: Hi, On Tue, Oct 8, 2013 at 3:21 AM, Richard Eisenberg e...@cis.upenn.eduwrote: We considered this for a while, but it led to a strange design -- to do it right, you would have to import all constructors for all datatypes *recursively* out to the leaves, starting at the datatypes mentioned in the class for which you wanted to use GND. This would mean potentially a whole lot of imports for symbols not actually used in the text of a program. I'm not sure I understand why constructors are involved in this. Wouldn't something like the following potentially be useful? data Role = Nominal | Representational | Phantom | Fun Role Role type family HasRole (t :: k) :: Role data MyData a b = MyData a data MyGADT a b where MyGADT :: MyGADT a Int type instance HasRole MyData = Fun Representational Phantom type instance HasRole MyGADT = Fun Representational Nominal type instance HasRole Traversable = Nominal HasRole instances would be automatically given by GHC. Cheers, Pedro ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: default roles
Perhaps I can spot the source of the confusion: there seem to be 2 different conversations going on here! 1: How to fit roles in with the ability to declare a datatype to be abstract. Should a library author be required to use a role annotation to make an abstract datatype, or should a library author be required to use a role annotation to allow GND with a datatype? 2: Some form of role abstraction, where an argument to a type parameter might get a representational role, depending on the role of some other variable. Using typeclasses is the current proposal for how to do this, and it in migmit's email below. Pedro also suggests a type families approach. My initial email was seeking advice on issue #1. As for #2: Using typeclasses here might be a decent surface syntax for the feature of role abstraction, but the automatic generation of instances, etc., would seem to require deep and pervasive magic under the hood. Essentially, every type and type variable would need to be annotated with both a kind and a role, significantly complicating GHC's type system. The question would be whether or not this upfront and ongoing investment is worth it. Thanks, Richard On Oct 8, 2013, at 10:49 AM, Miguel mig...@gmail.com wrote: I don't understand it either. Type family solution, however, seems wrong. See, if we, somehow, make something nominal when it has to be representational — well, some code won't compile, but nothing really bad happens. If, on the other hand, we by some miracle make something representational when in should be nominal — we can get a runtime error. It seems to be very similar to how type classes work, with nominal being the default, and representational a type class. Consider, for example, the Tricky example from the slides, slightly changed: data Tricky2 a b c = MkTricky2 (a c) (b c) Currently parameter c would be nominal. I suggest that it should be representational if and only if it's representational for BOTH a and b. WIth type classes it would be very simple: instance (HasRepresentationalParameter a, HasRepresentationalParameter b) = HasRepresentationalParameter (Tricky2 a b) With type families... well, apparently I don't have enough milliolegs to figure out how to do it. On Tue, Oct 8, 2013 at 12:01 PM, José Pedro Magalhães drei...@gmail.com wrote: Hi, On Tue, Oct 8, 2013 at 3:21 AM, Richard Eisenberg e...@cis.upenn.edu wrote: We considered this for a while, but it led to a strange design -- to do it right, you would have to import all constructors for all datatypes *recursively* out to the leaves, starting at the datatypes mentioned in the class for which you wanted to use GND. This would mean potentially a whole lot of imports for symbols not actually used in the text of a program. I'm not sure I understand why constructors are involved in this. Wouldn't something like the following potentially be useful? data Role = Nominal | Representational | Phantom | Fun Role Role type family HasRole (t :: k) :: Role data MyData a b = MyData a data MyGADT a b where MyGADT :: MyGADT a Int type instance HasRole MyData = Fun Representational Phantom type instance HasRole MyGADT = Fun Representational Nominal type instance HasRole Traversable = Nominal HasRole instances would be automatically given by GHC. Cheers, Pedro ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
RTS option -A affecting cpu-core usage?
Hi all, I played around with a parallel algorithm and tried to get the GC time down by specifying the RTS option '-A'. But if I'm specifying '-A' than also the usage of the cpu-cores seems to change. Without '-A' I'm getting a total cpu-core usage of '4.44s', with '-A' I'm getting only '1.67s'. Any ideas? Greetings, Daniel Without '-A': - dan@machine ~ ghc-mod-dev find showWindows +RTS -s -N4 XMonad.Util.XUtils 980,770,296 bytes allocated in the heap 552,122,168 bytes copied during GC 163,683,152 bytes maximum residency (11 sample(s)) 4,369,800 bytes maximum slop 280 MB total memory in use (0 MB lost due to fragmentation) Tot time (elapsed) Avg pause Max pause Gen 0 1690 colls, 1690 par2.45s0.66s 0.0004s0.0024s Gen 111 colls,10 par0.98s0.26s 0.0239s0.1022s Parallel GC work balance: 18.06% (serial 0%, perfect 100%) TASKS: 6 (1 bound, 5 peak workers (5 total), using -N4) SPARKS: 1025 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 1025 fizzled) INITtime0.00s ( 0.00s elapsed) MUT time0.99s ( 0.83s elapsed) GC time3.43s ( 0.93s elapsed) EXITtime0.02s ( 0.02s elapsed) Total time4.44s ( 1.78s elapsed) Alloc rate995,571,064 bytes per MUT second Productivity 22.7% of total user, 56.5% of total elapsed gc_alloc_block_sync: 53552 whitehole_spin: 0 gen[0].sync: 75 gen[1].sync: 23678 With '-A': -- dan@machine ~ ghc-mod-dev find showWindows +RTS -s -N4 -A500m XMonad.Util.XUtils 979,761,872 bytes allocated in the heap 94,043,424 bytes copied during GC 118,609,784 bytes maximum residency (2 sample(s)) 2,844,808 bytes maximum slop 2196 MB total memory in use (0 MB lost due to fragmentati Tot time (elapsed) Avg pause Ma Gen 0 0 colls, 0 par0.00s0.00s 0.s Gen 1 2 colls, 1 par0.47s0.18s 0.0878s Parallel GC work balance: 57.02% (serial 0%, perfect 100%) TASKS: 6 (1 bound, 5 peak workers (5 total), using -N4) SPARKS: 1025 (616 converted, 0 overflowed, 0 dud, 0 GC'd, 409 fizzl INITtime0.02s ( 0.02s elapsed) MUT time1.16s ( 1.16s elapsed) GC time0.47s ( 0.18s elapsed) EXITtime0.02s ( 0.02s elapsed) Total time1.67s ( 1.38s elapsed) Alloc rate844,914,346 bytes per MUT second Productivity 70.8% of total user, 85.9% of total elapsed gc_alloc_block_sync: 33458 whitehole_spin: 0 gen[0].sync: 5372 gen[1].sync: 0 ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: RTS option -A affecting cpu-core usage?
Ok, I think I got it. The cpu-cores are spending most of their time doing GC, by reducing the GC time the cpu-cores don't have anything left to do. Seems like a really great parallel algorithm ;). Greetings, Daniel ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
