Gambit-list Avril 2010

gambit-list@iro.umontreal.ca

16 participants
14 discussions

Edge triggered I/O with libevent
by Adam Langley 04 Avr '13

04 Avr '13

Gambit uses the select call on POSIX systems to multiplex IO operations. This is fine for small numbers of file descriptors, but falls apart quickly with large numbers[1]. libevent[2] is a wrapper library around a number of modern IO multiplexing systems (epoll on Linux, kqueue on the BSDs as well as poll and select). Attached is a patch which converts Gambit to using edge triggered I/O with epoll and libevent. This also requires a patch (attached) of libevent since the standard distribution doesn't include edge triggering support and the upstream appears to be on holiday. (epoll is required because I don't have a BSD box on which to develop edge triggering support for kqueue) This patch (for Gambit) preprocesses away to nothing unless --enable-libevent is passed to the configure script. (Note that, since this patches the configure.ac script, you'll need to run autoconf to regenerate). I hope I've not broken anything, but at this stage I've only tested that the console and tcp ports work. This patch (in the future) should also allow people, who write programs which use socket calls directly, to integrate into the main event loop at some point. Testing is more than welcome and, if you find a form of IO which is broken, please email me. [1] http://monkey.org/~provos/libevent/libevent-benchmark2.jpg [2] http://monkey.org/~provos/libevent/ -- Adam Langley agl(a)imperialviolet.org http://www.imperialviolet.org (+44) (0)7906 332512 PGP: 9113 256A CC0F 71A6 4C84 5087 CDA5 52DF 2CB6 3D60

2 2

How to pass a u8vector to the FFI
by Mikael 20 Sep '11

20 Sep '11

You do this, by declaring the passed u8vector as a scheme-object in the c-lambda definition. The memory pointer to the u8vector's contents in the C code is resolved by void *u8vectorptr = ___CAST(void*,&___FETCH_U8(___BODY(theu8vectorschemeobjectvariable),___INT(0))); Remember that the pointer is only to be kept until the next return to Scheme. Mikael 2010/3/30 Álvaro Castro-Castilla <alvaro.castro.castilla(a)gmail.com> > Hi! > > Is there a way to pass a u8-vector to a FFI interface somehow? > The way I expect this to work is through a (pointer unsigned-char), but it > obviously doesn't work, claiming a proper C pointer. I would like to be able > to build this arrays from Scheme code. Is there a way? > > Currently I have to call a FFI function to set char by char, calling the > c-lambda function too many times. > > One thing that could work is something that converts u8-vectors to unsigned > char* arrays, does that exist in Gambit? > > > Thanks, > > Álvaro > > _______________________________________________ > Gambit-list mailing list > Gambit-list(a)iro.umontreal.ca > https://webmail.iro.umontreal.ca/mailman/listinfo/gambit-list > >

6 10

Blackhole and match
by Marco Benelli 03 Jui '10

03 Jui '10

It seems to me that blackhole's match doesn't work: $ bsc Loaded Black Hole. Gambit v4.6.0 > (import (std misc/match)) > (match 2 (2 #t) (_ #f)) *** ERROR -- Unbound variable: module#extract-syntactic-closure-list I've also tried Alex Shinn's match: > (import lib/match) ; Alex Shinn's match > (match 2 (2 #t) (_ #f)) #t > (match 'foo ('foo #t) (_ #f)) *** ERROR -- Unbound pattern variable quote Maybe a bug with syntax-rules literals? I'm using the last master branch from github. --marco

2 4

Tags missing in upstream repository
by Christian Jaeger 30 Avr '10

30 Avr '10

Hello Marc The repository at http://www.iro.umontreal.ca/~gambit/repo/gambit.git is missing the release tags. (This has been for some time now, I've added the tags manually locally.) git push doesn't push tags unless they are specified as argument (or the --tags option is given). Also, the repo has more than 1800 loose objects (which makes it take 37 MB instead of ~9 MB to clone). I suggest you run "git config gc.auto 500" inside the repository on the server. The next push will then repack it. Christian.

1 0

Patches to allow to merge upstream with make update
by Christian Jaeger 30 Avr '10

30 Avr '10

Hello "make update" in upstream Gambit drops patches on the local branch; it doesn't merge. Since updating has to be done in steps, this poses a problem if one has local changes. This patch series solves this. I've tested it for some time now and it works without problems for me. Christian.

1 6

A couple patches
by Christian Jaeger 30 Avr '10

30 Avr '10

Hello I'm following up with a couple patches that haven't been merged to Gambit [yet]. Apply with git am. Christian.

1 5

Wii
by Sean Charles 25 Avr '10

25 Avr '10

Hi, I've cross-compiled Gambit Scheme using devkitPPC for a Wii. I have used the example Wii 'template' program as the basis for my initial efforts. My goal is to attempt to produce a Wii executable that has SLIME/EMACS capability and also has all of the good libraries linked in with FFI wrappers eg GRRLIB etc. This means that I should be able to run the Gambit version from the Homebrew Browser and then connect and develop remotely, ultimately using 'gsc' to produce the final stand-a-lone executable once the hacking is over. I've followed the efforts of James Long and managed to incorporate Gambit into some of my iPhone applications (none for sale yet!) so I know that it does cross-compile and does work, but for now, I am having great difficulties in getting *anything* except register dumps when I call a function defined with (c-define). I remember having similar issues on the iPhone but it was because on James' site, he hadn't fully described what he-d done but a few PM-s got that sorted just fine. Thanks James! First of all, here is how I built the gsc/gsi tools with devkitPPC, ./configure --prefix=/usr/local/Gambit-C/wii --enable-single-host=yes --host=powerpc-eabi That produces for me /usr/local/Gambit-C/wii/lib/libgambc.a and presumably it is PPC correct with respect to architecture. I then wrote a small test file called scode.scm in the same folder as the template.c program: (c-define (wii_blast ) () void "wii_blast" "extern" ;; stub 42) and use gsc -link scode.scm to produce the scode.c and scode_.c files which the Makefile picks up and uses. In the template.c file I declare it as... extern void wii_blast(); Every time I call it I get a register dump and I don't know why! I have reduced the function to void/void so as to remove any possibilities of stack corruption caused by incorrect push/pops due to a misinterpreted function signature etc, I cut my teeth 25 years ago with assembler and you never forget the basics! LOL. I have included the full template,c at the end of this mail along with the modified makefile incase anybody could tell me what is wrong. I am assuming that the build of 'libgambc.a' is fine because my program does call ___setup() and ___close() with no problems but they would appear to be native C functions and I am assuming that the wii_blast() function is maybe a byte-code thing happening or is it truly C code at this time? That is my ignorance of the internals of GambitC showing now. My next step is to try to produce a link map and a disassembly of the wii_blast function and then code a function foo: void foo(void) { } and compare the pre-call and post-call operations to see what is going on... in the meantime, if anybody cares to point out what I may/am doing wrong I would be most grateful as I really want to be able to build an interactive Wii development toolkit based on scheme, that wraps GRRLIB and libogc in the first instance. My *real* problem started from that fact that I wanted to be able to use the 'gsc -exe' route to build a complete Wii application in one pass i.e. have a main SCM file that pulls in everything else and then the --cc-options and --ld-options flags would do the rest.... the problem I had is that I couldn't work out how to tell the native gsc to use the target compilers in /opt/devkitpro/devkitPPC/bin !! Is it just setting 'CC' or GAMBC_CC_COMMAND etc etc? Either way, so far I am pleased with my progress but I am a little stuck right now! Marc Feely, if you are out there dude, got any tips? :) Thanks, Sean Charles.

2 1

Serial number longevity
by Mikael 21 Avr '10

21 Avr '10

Marc, What is the lifetime/longevity of serial numbers as returned by ( object->serial-number)? Thanks, Mikael * *

2 1

performance
by Álvaro Castro-Castilla 20 Avr '10

20 Avr '10

Hello, Using gambit 4.6.0 I have a performance problem. It may be my mistake, but I can't see the problem. So I decided to make tests and send them here, so maybe you can point it out. The program fills a 500x500 array or list with values corresponding to its 2d euclidean distance to a reference point (200,200). 1.3gz centrino (very old computer) Filling a 500x500 uchar* in C: 30 ms. Filling a 500x500 list in gambit interpreter: ~3200 ms. with two different approaches, both with integer arithmetic. If I use floating points it takes roughly double. Compiling the code drops to ~800ms. still quite high (and I don't usually compile the module when working with it). what could I do to improve this? is something wrong with my code? I attach the two versions. Thank you Álvaro

4 8

packages and reusable code
by Aditya Godbole 14 Avr '10

14 Avr '10

Hi all, I'm quite new to Scheme as such, though I have tinkered around with Gambit's ffi in the past. I am uncertain of the correct way of reusing code with Gambit. Possible options I have come across are slib, snow and black hole. What is the most preferred method of using other modules? If one of them has the functionality that I want, say, the zlib package in snow, and I have black-hole installed, what would be the best way around? TIA. -aditya

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Gambit-list Avril 2010