[cwn] Attn: Development Editor, Latest Caml Weekly News
Alan Schmitt
alan.schmitt at polytechnique.org
Mon Oct 16 23:46:08 PDT 2006
Hello,
Here is the latest Caml Weekly News, for the week of October 10 to
17, 2006.
1) ocamlopt under win32
2) forking, threads and events
3) Release 0.8 of demexp is out
4) Missing overflow exception message in ocamlopt
5) Ancient 0.8.0 & Weblogs 2.1 released
========================================================================
1) ocamlopt under win32
Archive: <http://groups.google.com/group/fa.caml/browse_thread/thread/
42ab6a1c67bda727/2f0bc128e0f968c3#2f0bc128e0f968c3>
------------------------------------------------------------------------
** Continuing a thread from last week, Philip A. Viton asked and Dr.
Axel Poigné answered:
> Can anyone tell me what's going wrong here?
> Computer: running win xp/sp2 on amd 64
> ocamlopt: 3.09.0
> ms files: from visual studio 6
> [...]
> libasmrun.lib(compact.obj) : error LNK2001: unresolved external
symbol
> __ftol2
This is a classic one. Just add
fix_ftol2.c
long _ftol2( double dblSource )
{ return _ftol( dblSource ); }
to your sources. At least that is what we did.
========================================================================
2) forking, threads and events
Archive: <http://groups.google.com/group/fa.caml/browse_thread/thread/
8976ccece284bf88/8156e60c80bdc1e0#8156e60c80bdc1e0>
------------------------------------------------------------------------
** Erik de Castro Lopo asked and Gerd Stolpmann answered:
> I'm thinking about to start a new project which has some rather
> critical requirements. It will be compiled with the native compiler
> initially targeting Linux/Unix but eventually also windoze.
> The app consists of a main engine which spawns many short lived
> child threads or processes. The children go away, do their work and
> then pass their results back to the main engine. Many of the children
> will spawn another process and read the child process output via a
> pipe and many of the children will block on I/O. A small portion of
> the children may be I/O bound, but there is not way of telling which
> beforehand.
> Since I would like to maximize the throughput on multi-core and
> multi-processor machines I am thinking of using a mix of forking and
> threading.
You know that there is no fork on Windows?
> For communications, I was thinking of using the Event
> module for communication between threads, but I don't think that
> works for forked process (pipes maybe?).
> Anybody have any advice for this project? Any war stories from
similar
> projects? Any readings they can recommend?
If there wasn't the Windows requirement I could recommend this:
You may have a look at ocamlnet2. It includes the netplex library that
manages parent/children relationships between either forked processes or
threads. You can use SunRPC for communication (or whatever you like, but
SunRPC support is included). The bad news is that it does not run on the
native Windows port, not even in the threaded variant (because there's
no socketpair...).
Ah yes, I have a war story, but cannot tell it now. I can only say it is
used for a really big commercial project.
Download it here:
<http://www.ocaml-programming.de/packages/ocamlnet-2.2test13.tar.gz>
An online manual is here:
<http://ocamlnet.sourceforge.net/manual-2.2/>
========================================================================
3) Release 0.8 of demexp is out
Archive: <http://groups.google.com/group/fa.caml/browse_thread/thread/
4e1a461793a0346a/5e8ed5026fdfcc5c#5e8ed5026fdfcc5c>
------------------------------------------------------------------------
** Felix HENRY announced:
demexp 0.8 is out! demexp is an electronic voting system for wide
scale direct democracy. demexp is developed mainly to support the
democractic experience project (<http://www.demexp.org>), but can be
used in other contexts (communities, firms, ...).
Briefly, demexp allows to ask questions ("votes"), to submit
answers to those questions ("candidate answers"), and to vote on
the submitted answers to elect a winning answer (using Condorcet voting
system).
demexp is implemented as a centralized server and a GTK2 graphical
client (a Drupal web client will be available soon). A classification
system allows to navigate through questions.
* What's new in 0.8?
- New configuration file that supports version upgrading;
- Support for client internationalization;
- Translations of the (English) client in French and Esperanto;
- Experimental web client in OCaml (using WDialog);
- Improvement of the Windows installer;
- simplification of the client's interface;
- tooltips on column titles;
- various bug fixes on the client and the server.
* How can I try it?
The most recent version of the sources (in OCaml) are here:
<http://www.linux-france.org/~dmentre/demexp/latest-src/>
Main code is under GNU General Public License (GPL). It relies on
external libraries and code of which licenses are GPL compatible
(see source code for details).
Once compiled use it to connect to the demonstration server:
$ demexp-gtk2-client demexp://demo.demexp.org:50000
Packages are also available for various Linux distributions (althought
most of them are not 0.8-ready yet). Have a loot at:
<http://www.demexp.org/fr/doku.php?id=telechargement_du_logiciel_demexp>
* Other links
Development: <http://savannah.nongnu.org/projects/demexp>
demexp software wiki: <http://www.demexp.org/en/>
Democratic experience political project: <http://www.demexp.org>
========================================================================
4) Missing overflow exception message in ocamlopt
Archive: <http://groups.google.com/group/fa.caml/browse_thread/thread/
cacd6900d7abe2ef/31e188c871bcb2e6#31e188c871bcb2e6>
------------------------------------------------------------------------
** Jakob Lichtenberg asked:
Using ocaml-3.09.3-win-msvc
When I compile the following program as byte code I see a stack overflow
(expected). When using ocamlopt it seems that the program dies and I do
not see the expected overflow exception?
>type overflow.ml
let array_1=Array.make 229376 42;;
let _ = Printf.printf "A\n";;
flush stdout;;
let array_2=Array.make 32768 43;;
let _ = Printf.printf "B\n";;
flush stdout;;
let list_1 = Array.to_list(array_1);;
let _ = Printf.printf "C\n";;
flush stdout;;
let list_2 = Array.to_list(array_2);;
let _ = Printf.printf "D\n";;
flush stdout;;
let list_3 = list_1 at list_2;;
let _ = Printf.printf "E\n";;
flush stdout;;
>ocamlc overflow.ml -o overflow_ocamlc.exe
>overflow_ocamlc.exe
A
B
C
D
Fatal error: exception Stack_overflow
>echo %ERRORLEVEL%
2
>ocamlopt overflow.ml -o overflow_ocamlopt.exe
>overflow_ocamlopt.exe
A
B
C
D
>echo %ERRORLEVEL%
-1073741819
Is this a bug?
** Xavier Leroy answered:
Right. Given your e-mail address, you might actually understand
better than I why it is so. Let me explain:
The machine code generated by ocamlopt does not test explicitly for
stack overflows, relying instead on the operating system to detect and
report them. However, handling of stack overflow conditions varies
greatly between processors and operating systems. Currently:
- Under Linux/IA32 and Linux/AMD64, stack overflows are properly
turned into a Stack_overflow Caml exception. Similar handling is
in the CVS for MacOSX/PPC, and MacOSX/Intel might be feasible soon.
- Other Unix-like operating systems just report stack overflows
as a "segmentation violation" or "bus error" fatal signal.
- Windows, as you noticed, behaves strangely. Stack overflows are
turned
into Win32 system exceptions, but apparently the structured
exception handling of Win32 just fails to handle them and silently
exits the program. That might be because the stack frames generated
by ocamlopt are nothing like what Win32 expects.
If you happen to know how to do better under Windows, you're most
welcome to let me know.
========================================================================
5) Ancient 0.8.0 & Weblogs 2.1 released
Archive: <http://groups.google.com/group/fa.caml/browse_thread/thread/
80cb9c27c3f45e7d/14c562ef9958151c#14c562ef9958151c>
------------------------------------------------------------------------
** Richard Jones announced:
We are pleased to announce the release of Ancient 0.8.0 and
Weblogs 2.1.
======================================================================
Ancient 0.8.0
The Ancient module allows you to use in-memory data structures which
are larger than available memory and so are kept in swap. If you try
this in normal OCaml code, you'll find that the machine quickly
descends into thrashing as the garbage collector repeatedly iterates
over swapped memory structures. This module lets you break that
limitation. Of course the module doesn't work by magic :-) If your
program tries to access these large structures, they still need to be
swapped back in, but it is suitable for large, sparsely accessed
structures.
Secondly, this module allows you to share those structures between
processes. In this mode, the structures are backed by a disk file,
and any process that has read/write access that disk file can map that
file in and see the structures.
(more here: <http://merjis.com/_file/ancient-readme.txt> )
----------------------------------------------------------------------
Differences in this release:
Previously a hard-coded limit of 1024 objects could be stored in one
backing file. This limit has now been removed.
----------------------------------------------------------------------
Download:
<http://merjis.com/developers/ancient>
======================================================================
Weblogs 2.1
Weblogs is an OCaml module for importing weblogs from Apache or IIS
web servers.
In this major release we have modified the API to use arrays of
structures instead of lists for efficiency. We have added support for
the Ancient module, so that absolutely huge logfiles can now be loaded
into memory and analysed. To give you an idea of how large: we have
analysed 38 GB of logfiles from one customer on a 64-bit desktop
machine with just 2 GB of physical RAM.
----------------------------------------------------------------------
Download:
<http://merjis.com/developers/weblogs>
======================================================================
Both modules are released under LGPL + OCaml linking exception, to
make them compatible with the OCaml library and maximise use even in
commercial applications.
========================================================================
Using folding to read the cwn in vim 6+
------------------------------------------------------------------------
Here is a quick trick to help you read this CWN if you are viewing it
using
vim (version 6 or greater).
:set foldmethod=expr
:set foldexpr=getline(v:lnum)=~'^=\\{78}$'?'<1':1
zM
If you know of a better way, please let me know.
========================================================================
Old cwn
------------------------------------------------------------------------
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========================================================================
--
Alan Schmitt <http://alan.petitepomme.net/>
The hacker: someone who figured things out and made something cool
happen.
.O.
..O
OOO
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