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Today's Topics:
1. Re: Lazy vs Strict ponderings... (Heinrich Apfelmus)
2. haskell install on low memory server? (Rob Nikander)
3. Re: haskell install on low memory server? (Felipe Almeida Lessa)
4. Re: haskell install on low memory server? (Rob Nikander)
5. Re: haskell install on low memory server? (Felipe Almeida Lessa)
6. Re: haskell install on low memory server? (Daniel Fischer)
7. Re: Using Iteratees to write to a file (Magnus Therning)
8. Re: haskell install on low memory server? (Rob Nikander)
----------------------------------------------------------------------
Message: 1
Date: Sat, 19 Mar 2011 12:50:18 +0100
From: Heinrich Apfelmus <apfel...@quantentunnel.de>
Subject: Re: [Haskell-beginners] Lazy vs Strict ponderings...
To: beginners@haskell.org
Message-ID: <im259q$78c$1...@dough.gmane.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Sean Charles wrote:
> I *think* I understand about lazy evaluation and its effects on I/O and
> that it can internally create thunks, promises, continuations etc.
> whatever you want to call them, and then at some point there will be a
> sudden spike in memory and CPU loads as something triggers a whole chain
> of promises to be fulfilled but what I don't have a feel for is just how
> serious a problem that might be today in say, a simple desktop application.
>
> [...]
>
> Is it something one needs to worry about at all or should one just code
> away and write the application and then worry!?
>
> I think that having a clearer understanding of what 'types' of problems
> and their implementations have on CPU/RAM would be a good one to have!
The practitioner's approach to laziness is usually the following
sequence of approximations, which could be called "the lazy approach to
laziness":
0) Don't worry about performance. Write programs that are correct
instead. Laziness helps a lot with writing clean and compositional code.
Example:
zipWith (,) [1..] xs
1) Look out for common laziness gotchas. There are essentially only two
of them:
i) Unevaluated expressions that take way more space
than their evaluated forms. Prototypical example
foldl (+) [1..n]
ii) Memory leaks due to sharing. Prototypical example
average xs = sum xs / length xs
2) Don't worry about memory leaks until they actually appear. If they
do, use a profiling tool to find out what's going on. Most likely, one
of the two things above happened in an interesting way.
Note that you might want to be a bit more careful when writing a real
time system. In that case, would suggest to only use abstractions whose
performance is easy to reason about and to keep the core code fairly
small, so that you have a clear picture of what is going on. Other than
that, there is no need to worry about garbage collection or laziness.
Regards,
Heinrich Apfelmus
--
http://apfelmus.nfshost.com
------------------------------
Message: 2
Date: Sat, 19 Mar 2011 10:14:31 -0400
From: Rob Nikander <rob.nikan...@gmail.com>
Subject: [Haskell-beginners] haskell install on low memory server?
To: beginners@haskell.org
Message-ID:
<AANLkTim2=wt4rmd-uy1v9w-yp+tgdb+cr+ycewqth...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hi,
I'd like to install Haskell on a linux virtual server with about 600
MB of RAM. (Maybe that is doomed to failure?) The goal is to try
"happstack" for web apps, behind nginx. Compiling the whole platform
is asking for OpenGL... so I thought I would get cabal and install
pieces that I want. I downloaded the 'generic ghc binary' from here:
http://hackage.haskell.org/platform/linux.html and that seems to work.
But when I download the cabal-install tarball and try to run it's
'bootstrap.sh' I run out of memory. Is there a way to tell it to use
less memory?
------- shell commands -------
$ cd cabal-install-0.10.2
$ sh bootstrap.sh
Checking installed packages for ghc-7.0.2...
Cabal is already installed and the version is ok.
transformers-0.2.2.0 will be downloaded and installed.
mtl-2.0.1.0 will be downloaded and installed.
parsec-3.1.1 will be downloaded and installed.
network-2.3.0.2 will be downloaded and installed.
time is already installed and the version is ok.
HTTP-4000.1.1 will be downloaded and installed.
zlib-0.5.3.1 will be downloaded and installed.
Downloading transformers-0.2.2.0...
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 17148 100 17148 0 0 27246 0 --:--:-- --:--:-- --:--:-- 39420
[1 of 1] Compiling Main ( Setup.hs, Setup.o )
Linking Setup ...
collect2: ld terminated with signal 9 [Killed]
Error during cabal-install bootstrap:
Compiling the Setup script failed
------- end of shell commands -------
It seems strange that `ld` would need to use ~450 MB, which is what
it's doing to get killed by the kernel.
Any ideas?
thanks,
Rob
------------------------------
Message: 3
Date: Sat, 19 Mar 2011 14:25:21 +0000
From: Felipe Almeida Lessa <felipe.le...@gmail.com>
Subject: Re: [Haskell-beginners] haskell install on low memory server?
To: Rob Nikander <rob.nikan...@gmail.com>
Cc: beginners@haskell.org
Message-ID:
<AANLkTi=eh3q+ggshmp5mpry7jogdrt9aupfx-py0a...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
On Sat, Mar 19, 2011 at 2:14 PM, Rob Nikander <rob.nikan...@gmail.com> wrote:
> Hi,
>
> I'd like to install Haskell on a linux virtual server with about 600
> MB of RAM. ?(Maybe that is doomed to failure?) ?The goal is to try
> "happstack" for web apps, behind nginx. ?Compiling the whole platform
> is asking for OpenGL... so I thought I would get cabal and install
> pieces that I want. ?I downloaded the 'generic ghc binary' from here:
> http://hackage.haskell.org/platform/linux.html and that seems to work.
> ?But when I download the cabal-install tarball and try to run it's
> 'bootstrap.sh' I run out of memory. ?Is there a way to tell it to use
> less memory?
You don't really need to compile GHC by yourself on the memory
constrained machine. First of all, you may use a binary distribution.
And second, you may compile on a different machine with more RAM.
That said, compiling Haskell programs on such low memory computers
isn't really difficult, provided your program isn't as big as GHC.
I've been succesfully using an AWS micro instance with 595 MiB of RAM
and an Yesod app. (But I have some swap memory should it be needed.)
HTH, =)
--
Felipe.
------------------------------
Message: 4
Date: Sat, 19 Mar 2011 10:41:50 -0400
From: Rob Nikander <rob.nikan...@gmail.com>
Subject: Re: [Haskell-beginners] haskell install on low memory server?
To: Felipe Almeida Lessa <felipe.le...@gmail.com>
Cc: beginners@haskell.org
Message-ID:
<AANLkTikO1zDVhn9hJxROpEhfzCcQfav-KC85NJSA=s...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
On Sat, Mar 19, 2011 at 10:25 AM, Felipe Almeida Lessa
<felipe.le...@gmail.com> wrote:
> On Sat, Mar 19, 2011 at 2:14 PM, Rob Nikander <rob.nikan...@gmail.com> wrote:
>> ...
>> is asking for OpenGL... so I thought I would get cabal and install
>> pieces that I want. ?I downloaded the 'generic ghc binary' from here:
>> http://hackage.haskell.org/platform/linux.html and that seems to work.
>> ?But when I download the cabal-install tarball and try to run it's
>> 'bootstrap.sh' I run out of memory. ?Is there a way to tell it to use
>> less memory?
>
> You don't really need to compile GHC by yourself on the memory
> constrained machine. ?First of all, you may use a binary distribution.
> ?And second, you may compile on a different machine with more RAM.
But I'm not compiling GHC, am I? I downloaded the binary, and it
works. I thought I was trying to install cabal, because I don't see
it included in the GHC binaries.
>From the error message in my previous email, it looks like it dies
trying to compile "transformers".
I also have a Micro EC2 instance. If there was a 'yum' haskell
package for this "Amazon Linux" I'd use that, but I don't see one.
thanks,
Rob
------------------------------
Message: 5
Date: Sat, 19 Mar 2011 15:02:15 +0000
From: Felipe Almeida Lessa <felipe.le...@gmail.com>
Subject: Re: [Haskell-beginners] haskell install on low memory server?
To: Rob Nikander <rob.nikan...@gmail.com>
Cc: beginners@haskell.org
Message-ID:
<aanlktinz2lm40pvm8upjjfmoy9aoehrz8rqivyf+o...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
On Sat, Mar 19, 2011 at 2:41 PM, Rob Nikander <rob.nikan...@gmail.com> wrote:
> But I'm not compiling GHC, am I? ?I downloaded the binary, and it
> works. ?I thought I was trying to install cabal, because I don't see
> it included in the GHC binaries.
I think I have misunderstood your snippet. =)
> From the error message in my previous email, it looks like it dies
> trying to compile "transformers".
Yes, that seems so.
> I also have a Micro EC2 instance. ?If there was a 'yum' haskell
> package for this "Amazon Linux" I'd use that, but I don't see one.
I have installed Ubuntu on my micro instance and downloaded GHC from
there. However I've installed many other packages through cabal.
Perhaps the difference is the swap file?
You may try
# dd if=/dev/zero of=/tmp/swap bs=1M count=1024
# mkswap /tmp/swap
# swapon /tmp/swap
HTH, =)
--
Felipe.
------------------------------
Message: 6
Date: Sat, 19 Mar 2011 16:11:21 +0100
From: Daniel Fischer <daniel.is.fisc...@googlemail.com>
Subject: Re: [Haskell-beginners] haskell install on low memory server?
To: beginners@haskell.org
Message-ID: <201103191611.21851.daniel.is.fisc...@googlemail.com>
Content-Type: Text/Plain; charset="iso-8859-1"
On Saturday 19 March 2011 15:14:31, Rob Nikander wrote:
> Hi,
>
> I'd like to install Haskell on a linux virtual server with about 600
> MB of RAM. (Maybe that is doomed to failure?) The goal is to try
> "happstack" for web apps, behind nginx. Compiling the whole platform
> is asking for OpenGL... so I thought I would get cabal and install
> pieces that I want. I downloaded the 'generic ghc binary' from here:
> http://hackage.haskell.org/platform/linux.html and that seems to work.
> But when I download the cabal-install tarball and try to run it's
> 'bootstrap.sh' I run out of memory. Is there a way to tell it to use
> less memory?
>
> ------- shell commands -------
>
> $ cd cabal-install-0.10.2
> $ sh bootstrap.sh
> Checking installed packages for ghc-7.0.2...
> Cabal is already installed and the version is ok.
> transformers-0.2.2.0 will be downloaded and installed.
> mtl-2.0.1.0 will be downloaded and installed.
> parsec-3.1.1 will be downloaded and installed.
> network-2.3.0.2 will be downloaded and installed.
> time is already installed and the version is ok.
> HTTP-4000.1.1 will be downloaded and installed.
> zlib-0.5.3.1 will be downloaded and installed.
>
> Downloading transformers-0.2.2.0...
> % Total % Received % Xferd Average Speed Time Time Time
> Current Dload Upload Total Spent Left Speed 100 17148 100
> 17148 0 0 27246 0 --:--:-- --:--:-- --:--:-- 39420 [1 of
> 1] Compiling Main ( Setup.hs, Setup.o )
> Linking Setup ...
> collect2: ld terminated with signal 9 [Killed]
That means it's OOM-killed while linking the setup script?
That should not be (nor should it be OOM when compiling any of those
packages).
Although, I just tested and linking the default Setup.hs used 300MB here,
so 450MB is not impossible.
There's a lot to link in from the Cabal library, perhaps also the ghc-api
(the unstripped executable was 5.6MB, which is surprisingly huge, the
stripped is still 3.1MB, normally executables are smaller).
>
> Error during cabal-install bootstrap:
> Compiling the Setup script failed
>
> ------- end of shell commands -------
>
> It seems strange that `ld` would need to use ~450 MB, which is what
> it's doing to get killed by the kernel.
>
> Any ideas?
You could try installing them (and afterwards cabal-install) the old way,
$ runghc ./Setup.hs configure --user
$ runghc ./Setup.hs build
$ runghc ./Setup.hs install
But if ghc is killed linking the default setup script, it will probably get
killed each time you try to cabal install a package because that involves
linking a setup script.
>
> thanks,
> Rob
------------------------------
Message: 7
Date: Sat, 19 Mar 2011 16:29:54 +0000
From: Magnus Therning <mag...@therning.org>
Subject: Re: [Haskell-beginners] Using Iteratees to write to a file
To: beginners@haskell.org
Message-ID: <20110319162954.GB7489@ohann>
Content-Type: text/plain; charset="us-ascii"
On Sat, Mar 19, 2011 at 01:01:46AM -0700, Richard Wallace wrote:
> Hello everyone,
>
> I've been reading "Iteratee: Teaching an Old Fold New Tricks" from
> the Monad Reader Issue 16 and am having a problem figuring out how
> to use the streamToFile function. Specifically, I can't figure out
> how to feed the Iteratee data to write to the file. If I run
>
> ghci> runIter $ streamToFile "/tmp/stream"
>
> Then the file is created but not populated with any data - which is
> natural since I didn't give it any data. I have no clue how to give
> it data though. I'd really appreciate it if someone could show me
> how to write "Hello world!" or something else equally mundane to get
> me going. I've been banging my head on this for hours now.
I think you need to get your data from somewhere, an Enumerator, e.g.
an Enumerator for a file handle. I haven't looked at the Iteratee API
for a while, but I believe that an Enumerator basically is of the type
Iteratee -> Iteratee, which means that something along the lines of
runIter $ enumerateHandle h (streamToFile "/tmp/stream")
ought to copy the content of the handle into the file.
The documentation for Enumerator[1] is an excellent resource for
understanding iteratees. Even if you don't plan on using the
Enumerator package itself.
/M
[1] http://hackage.haskell.org/package/enumerator
--
Magnus Therning OpenPGP: 0xAB4DFBA4
email: mag...@therning.org jabber: mag...@therning.org
twitter: magthe http://therning.org/magnus
Most software today is very much like an Egyptian pyramid with
millions of bricks piled on top of each other, with no structural
integrity, but just done by brute force and thousands of slaves.
-- Alan Kay
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------------------------------
Message: 8
Date: Sat, 19 Mar 2011 13:17:39 -0400
From: Rob Nikander <rob.nikan...@gmail.com>
Subject: Re: [Haskell-beginners] haskell install on low memory server?
To: Felipe Almeida Lessa <felipe.le...@gmail.com>
Cc: beginners@haskell.org
Message-ID:
<aanlktikpfjeqsnurvwhhpnunb6epu512+l6uvygfu...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
On Sat, Mar 19, 2011 at 11:02 AM, Felipe Almeida Lessa
<felipe.le...@gmail.com> wrote:
> You may try
>
> # dd if=/dev/zero of=/tmp/swap bs=1M count=1024
> # mkswap /tmp/swap
> # swapon /tmp/swap
Thanks, with the swap space it is now compiling.
Rob
------------------------------
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