Here is the latest Caml Weekly News, for the week of September 09 to 16, 2008.
Archive: http://groups.google.com/group/fa.caml/browse_thread/thread/b59e481d78086488#François Pottier announced:
It is my pleasure to announce a new release of Menhir, with the following main improvements over previous versions: --table Menhir now supports producing table-based LR automata, in the tradition of yacc, bison, and ocamlyacc. This makes the generated parsers up to 5x smaller, and somewhat slower. --interpret Menhir can now be used not just as a compiler, but also as an interpreter. It will read sentences off the standard input channel, parse them as per your grammar, and report an outcome. This should help debug grammars. These new features were implemented by Guillaume Bau, Raja Boujbel, and François Pottier. We would like to gratefully acknowledge the generous support of Jane Street Capital LLC, who funded this endeavor through an ocaml summer project. As usual, the new release is available either through GODI, or as source code at the following URL. http://cristal.inria.fr/~fpottier/menhir/ Enjoy! Comments and bug reports are welcome.Julia Lawall asked and François Pottier replied:
> I was very excited about this option, because it drops the size of the > generated code for my parser from 61K LOC to 28K LOC. But unfortunately > it gives me: > > Unbound module MenhirLib.TableInterpreter.Make > > when I try to compile. Yup. I didn't write the details in the announcement; maybe I should have. When a parser is produced using --table, it is not quite stand-alone: it must be linked with a new library, called MenhirLib. (This is analogous to ocaml's Parsing module, which is part of the standard library.) If you are using ocamlfind, this is quite easy: just add "-package menhirLib" to your ocamlc/ocamlopt flags (for compiling and for linking), and add "-linkpkg" to your ocamlc/ocamlopt flags (for linking). If you do not wish to rely on ocamlfind, then things become slightly more complicated, since you must tell ocamlc/ocamlopt where MenhirLib is installed. Fortunately, Menhir itself can help you: it has three new command-line switches, of the form --suggest-*, which cause it to print suggested flags. The details are in Menhir's reference manual. The sample Makefile (demos/Makefile.shared) offers an illustration.
Archive: http://groups.google.com/group/fa.caml/browse_thread/thread/d2c476c866f86a04#Joel Reymont asked and Gerd Stolpmann replied:
> Suppose I want to build a server that runs on top of ocamlnet and > handles 10k+ connections. > > ocamlnet seems to use select exclusively. There's also netplex in ocamlnet, which is a kind of fork framework. I don't know which protocol you want to use. For instance, you can arrange that netplex starts 100 processes and every process handles 100 connections. > Any suggestions on how to add kernel poll? Is this possible even? I'm in the middle of changing ocamlnet here, so we can have more flexibility for choosing the kind of event polling. Look at the svn version: https://godirepo.camlcity.org/svn/lib-ocamlnet2/trunk/code/ There's a lot of new stuff in the src/netsys directory. In the future, all polling will be based on the pollset class type (src/netsys/netsys_pollset.mli). There is currently an implementation that uses the poll() syscall (src/netsys/netsys_pollset_posix.mli) and another one for Win32 (src/netsys/netsys_pollset_win32.mli - limited to sockets and named pipes for now). As this is a class type you can also go ahead, and implement it for every kernel mechanism you like, and just you your class instead of the classes provided by ocamlnet. I'll add some more mechanisms later (any help is welcome). You can turn these pollsets into event_system by using src/equeue/unixqueue2.mli. This is not very much tested, however, and there is no support for multi-threading yet in this module. Many ocamlnet modules allow to inject whatever event_system you like to have (should be all modules in the future). All this is experimental for now. I have tested it only with small programs, not with large production systems. But maybe it's an option for you to use the svn version.Markus Mottl also replied:
The Core-library that we developed at Jane Street, and which is also in Godi, contains a module "Linux_ext", which has a fully-featured interface to epoll (besides lots of other Linux-specific goodies). There you just call "Epoll.create" to get a file descriptor on which to listen for I/O-events. Then you only need to add other file descriptors you want to monitor with "Epoll.add", specifying flags for the kind of events you want to wait for. "Epoll.modify" and "Epoll.del" modify event flags of and remove monitored descriptors respectively. "Epoll.wait" allows you to wait for received events (similar to "select"). Note, however, that "select" is usually more efficient for small (= tens) numbers of descriptors!Mattias Engdegård also replied:
There is an ocaml wrapper for libevent: http://www.xs4all.nl/~mmzeeman/ocaml/ With that many connections, you may actually benefit from multiple processors, which in the OCaml world usually means multiple processes. There's nothing wrong with serving myriads of connections from a single process, especially when using a strongly typed language, but parallelism can be useful. On the other hand, one process per connection may be inefficient as well - a hybrid N:M solution is probably best.
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