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Number of outstanding messages in Chan or TChan
by Joel Reymont 06 Dec '05

06 Dec '05

Is there a way to check the number of outstanding messages in a Chan or TChan? I suspect my problem is related to not reading messages fast enough and I'd like to troubleshoot this by scanning my channels once every few seconds and dumping statistics. Thanks, Joel -- http://wagerlabs.com/

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RE: [Haskell-cafe] Re: :t main
by Scherrer, Chad 06 Dec '05

06 Dec '05

> From: Simon Peyton-Jones [mailto:simonpj@microsoft.com] > > I've not been following this thread, but I wanted to check: > you do know about Tarmo Uustalu's stuff about comonads, don't you? > > http://www.cs.helsinki.fi/u/ekarttun/comonad/ summarises > (link to "The essence of dataflow programming" at the bottom) > > Simon > Thanks, Simon. I've seen it, but I haven't fully digested it yet. Dataflow programming is new to me, and it's not immediately obvious how it ties in with IO in general. I'll take another look, though. Chad Scherrer Computational Mathematics Group Pacific Northwest National Laboratory "Time flies like an arrow; fruit flies like a banana." -- Groucho Marx

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Re: [Haskell-cafe] Learning Haskell
by Donn Cave 06 Dec '05

06 Dec '05

Quoth Lemmih <lemmih(a)gmail.com>: ... | You might wanna have a look at Don's FastPackedString library: | http://www.cse.unsw.edu.au/~dons/fps.html Thanks, that's actually what got me thinking about trying this again. | > | I am also hoping to use it for web development. | > | > Wonder how `links' is coming along. (Hope they figured out a better | > name, anyway.) | | Got an url for the project? http://homepages.inf.ed.ac.uk/wadler/links/ Having looked it up, of course I looked at it. Please forget I asked. Donn Cave, donn(a)drizzle.com

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RE: TChan implementation: Why TVarList
by Simon Peyton-Jones 06 Dec '05

06 Dec '05

The mutable cell is in the tail. A [TVar a] would be quite different. You can read about a very similar impl (based on MVars) in the original "Concurrent Haskell" paper (on my papers page) S | -----Original Message----- | From: Joel Reymont [mailto:joelr1@gmail.com] | Sent: 06 December 2005 11:28 | To: Simon Peyton-Jones | Cc: Haskell Cafe | Subject: TChan implementation: Why TVarList | | Simon, | | Why did you guys implement TChan on top of your own TVarList instead | of a regular list? | | -- | 'TChan' is an abstract type representing an unbounded FIFO channel. | data TChan a = TChan (TVar (TVarList a)) (TVar (TVarList a)) | | type TVarList a = TVar (TList a) | data TList a = TNil | TCons a (TVarList a) | | Thanks, Joel | | -- | http://wagerlabs.com/ | | | |

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RE: [Haskell-cafe] What's a thread doing / Erlang-style processes /Message passing
by Simon Marlow 06 Dec '05

06 Dec '05

On 06 December 2005 10:28, Joel Reymont wrote: > I'm finding myself in dire need of monitoring the Haskell runtime. > More precisely, I would like to know what each that I launch is doing > at a given point in time. > > Is there a way to obtain this information now? I would be fine with > knowing if a thread is blocking on a foreign call, MVar or something > like that. If you compile with -debug, and run with +RTS -Ds you get a scheduler trace which might help. Cheers, Simon

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RE: [Haskell-cafe] Signal 2 and -threaded
by Simon Marlow 06 Dec '05

06 Dec '05

On 06 December 2005 10:59, Joel Reymont wrote: > I'm seeing some funky behavior in my program compiled with -threaded. > It runs for a little while and then catches signal 2 and quits. This > does not happen when -threaded is not used. > > I'm compiling my library with -threaded so that is always constant. > The above applies to my main module and another module that is part > of it. > > Any ideas? I don't know any reason your program should be getting signal 2 (SIGINT, I assume), unless the program sends itself SIGINT or someone else does. Maybe on your system a process gets SIGINT when it exceeds some resource limit? Have you tried strace or equivalent (truss?)? Cheers, Simon

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RE: [Haskell-cafe] Re: TChan implementation: Why TVarList
by Simon Peyton-Jones 06 Dec '05

06 Dec '05

sounds as if you need a priority queue, so you can say "give me the message with the earliest time" but otherwise yes. Simon | -----Original Message----- | From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Joel | Reymont | Sent: 06 December 2005 11:46 | To: Simon Peyton-Jones | Cc: Haskell Cafe | Subject: [Haskell-cafe] Re: TChan implementation: Why TVarList | | Well, I meant more like TVar [a] but I see that you are pulling from | the front and appending to the rear. | | I need to implement a mailbox where messages can be pulled out based | on a predicate or in order of arrival. I'm thinking of using a Map | keyed on ClockTime. | | Do you have any suggestions? | | Thanks, Joel | | On Dec 6, 2005, at 11:31 AM, Simon Peyton-Jones wrote: | | > The mutable cell is in the tail. A [TVar a] would be quite different. | > You can read about a very similar impl (based on MVars) in the | > original | > "Concurrent Haskell" paper (on my papers page) | | -- | http://wagerlabs.com/ | | | | | | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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TChan implementation: Why TVarList
by Joel Reymont 06 Dec '05

06 Dec '05

Simon, Why did you guys implement TChan on top of your own TVarList instead of a regular list? -- | 'TChan' is an abstract type representing an unbounded FIFO channel. data TChan a = TChan (TVar (TVarList a)) (TVar (TVarList a)) type TVarList a = TVar (TList a) data TList a = TNil | TCons a (TVarList a) Thanks, Joel -- http://wagerlabs.com/

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Signal 2 and -threaded
by Joel Reymont 06 Dec '05

06 Dec '05

I'm seeing some funky behavior in my program compiled with -threaded. It runs for a little while and then catches signal 2 and quits. This does not happen when -threaded is not used. I'm compiling my library with -threaded so that is always constant. The above applies to my main module and another module that is part of it. Any ideas? I decided to compile with -threaded because otherwise killThread seems to block when a thread is in a foreign call. Thanks, Joel -- http://wagerlabs.com/

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RE: [Haskell-cafe] GADT question
by Simon Peyton-Jones 06 Dec '05

06 Dec '05

| I would like the type system to distinguish the three types and enforce | their properties. so far, I have come up with the following: | | | data Sigma | data Tau | data Rho | | data Type a where | ForAll :: [Id] -> Type Rho -> Type Sigma | Fun :: Type a -> Type a -> Type a | TyCon :: TyCon -> Type Tau | TyVar :: TyVar -> Type Tau It looks as if you want a kind of subtyping relationship, so that Tau < Rho < Sigma. The standard way to achieve that is using polymorphism (see, for example, papers about FFI to object-oriented languages) data Sigma a = S a data Rho a = R a data Tau = Tau data Type a where | ForAll :: [Id] -> Type (Sigma (Rho a)) -> Type (Sigma b) | Fun :: Type a -> Type a -> Type a | TyCon :: TyCon -> Type (Sigma (Rho Tau)) | TyVar :: TyVar -> Type (Sigma (Rho Tau)) I'm not sure if this would work. Simon

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