Gambit-list Septembre 2011

gambit-list@iro.umontreal.ca

21 participants
15 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

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Benchmark
by Sascha Ziemann 29 Sep '11

29 Sep '11

Is the benchmark suite that produced the following results available? http://www.iro.umontreal.ca/~gambit/bench.html The results look a bit out dated. It would be nice to have a package so that everybody can try the benchmarks.

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HTTP client Re: New project
by Mikael 28 Sep '11

28 Sep '11

Sack https://github.com/pereckerdal/sack provides a very nice HTTP client library. For credits and license see source files. It's written atop BH, and can easily be exploded out to be run atop load/include. There is one or two updates to the HTTP client functionality in the attached version that are not committed to the github repo yet. To our knowledge it works perfectly. Currently non-HTTP compliant server response may cause an internal exception. Thanks, Mikael 2011/9/12 Alex Queiroz <asandroq(a)gmail.com> > Hallo, > > On Fri, Sep 9, 2011 at 6:28 PM, Steve Graham <jsgrahamus(a)yahoo.com> wrote: > > Although I have programmed for decades, I am new to Scheme/Gambit. I > > thought that I would use a project I've been contemplating as a help in > > learning the language. > > There is a website of scriptures which I wish to download. Some of the > > webpages, of course, are indices into books and then chapters. So I > would > > need to follow the links until I got to the actual text, which I would > then > > file into a database by volume, book, chapter and verse. > > I would appreciate any hints as to how to do this. I'm thinking I would > > need some help with downloading web pages, stripping HTML and saving to a > > database. > > For downloading the page Gambit already gives you TCP sockets but you > would have to write the code for HTTP GET, which is not complex. For > parsing the HTML you will need SSAX[1], there is a "package" for it in > the Dumping Grounds[2]. Also in the Dumping Grounds you will find > several database interfaces. > > [1] - http://ssax.sourceforge.net/ > [2] - > http://dynamo.iro.umontreal.ca/~gambit/wiki/index.php/Dumping_Grounds > > Cheers, > -- > -alex > http://www.artisancoder.com/ > _______________________________________________ > Gambit-list mailing list > Gambit-list(a)iro.umontreal.ca > https://webmail.iro.umontreal.ca/mailman/listinfo/gambit-list >

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interfacing u16vector from the inside of a c-lambda
by Christopher Dutchyn 24 Sep '11

24 Sep '11

Here is a simple piece of code to do it: ;; double each element of v (with length n) in place (define double! (c-lambda (scheme-object int) ; the vector and it's length void "//extract array from scheme object ___U16* v = ___CAST(___U16*, ___BODY_AS(___arg1, ___tSUBTYPED)); // perform the C operations int i; for (i=0; i<___arg2; i+=1) { v[i] += v[i]; }")) (define *v* (u16vector 0 1 2 3 4 5)) (display *v*) (newline) (double! *v* (u16vector-length *v*)) (display *v*) For more details, the Gambit site, specifically http://dynamo.iro.umontreal.ca/~gambit/wiki/index.php/Using_Gambit_with_Ext… has many details. Chris D.

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interfacing u16vector from the inside of a c-lambda
by A.K.M.Rasheduzzamn Chowdhury 23 Sep '11

23 Sep '11

Hi All, The following Scheme code, loop-through-vector iterates through the u16vector v and increments the elements of v. (define v (make-u16vector 10 0)) (define (loop-through-vector length) (let loop ([j 0]) (if(< j length) (begin (u16-vectorset! v j (+ j 1)) (loop (+ j1)))))) (define (main) (loop-through-vector (u16vector-length v)) (main) My question is how can I implement loop-through-vector using c-lambda. Most important thing is how can i access u16vector from c-code. If anyone can give me the code for loop-through-vector using c-lambda, that would be so helpful. Or ,is there alternate solutions other than c-lambda. Regards, Rashed

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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 > >

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OT: Scraping data from Windows app screen
by Steve Graham 17 Sep '11

17 Sep '11

I need to pick up the text (field prompts and data) from a data entry screen. Is there a utility which could do such? An array of text by rows would be preferable, but other formats would likely suffice. Thanks, Steve

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Android Gambit Error
by Steve Graham 15 Sep '11

15 Sep '11

I've been studying "A Tour of Scheme in Gambit" and using Android Gambit (AG) to go through some of the exercises. I came across the following interesting lesson and decided to try it. And after I entered it into AG, the system did not come back from the repl. Gambit v4.6.1 > (define (counter) (let ((value 0)) (lambda () (set! value (+ value 1)) value))) I tried sending it via the Share functionality to a different e-mail address than my Google address and it did not deliver it, although I could see it in the Gmail Sent folder. I then tried sending it to the Gmail address and that did work fine. I noticed each time after sharing and then returning to the repl, there was a new prompt; however, I could not get the system to respond. The only thing that worked was killing the AG task and restarting AG. On a final note, I am mystified as to how the code works. This is an example of it being defined and run on my Windows 7x64 machine: Gambit v4.6.1 > (define (counter) (let ((value 0)) (lambda () (set! value (+ value 1)) value))) > (define first-counter (counter)) > (first-counter) 1 > (first-counter) 2 > (first-counter) 3 > (first-counter) 4 > It seems to initialize value to 0 and I assume that happens the first time you use (counter) to define another form. What I don't understand is why the code for initializing is skipped every time (first-counter) is run. TIA, Steve

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Re: [gambit-list] Too many open files with process
by Adam King 14 Sep '11

14 Sep '11

Still seems to hold on to a file handle somewhere :( Marc - is there any chance you could have a look - or try to replicate under OSX? I've looked through _io.scm and at the ##open-process-generic prim, but it's still over my head. I really would like to use Gambit for some scripting duties over all our game data (thousands of media files). Thanks, Adam On Fri, Sep 9, 2011 at 5:36 PM, Mikael <mikael.rcv(a)gmail.com> wrote: > Huh. Just for more debug, what about, for each process port created, make a > copy of it but with a weak GC reference, then after with-input-from-process > is done do ##gc, and check if the port still exists. Does it? Mikael > > > 2011/9/10 Adam King <akingcoder(a)gmail.com> > >> I placed a #gc in two different locations (before and after each call to >> (do-process)), but still the same error message. I also tried with a >> compiled version, same issue. Thanks for the suggestion though. >> >> Adam >> >> >> >> On Fri, Sep 9, 2011 at 5:16 PM, Mikael <mikael.rcv(a)gmail.com> wrote: >> >>> (While making a real solution to the problem, and as a part of debugging, >>> run ##gc right at the end of each do-process . Does it have any effect?) >>> >>> 2011/9/9 Adam King <akingcoder(a)gmail.com> >>> >>>> I need to descend a directory structure with ~5000 files in it and run >>>> an external process on each to gether information on each file. However, >>>> after running over about 250 files, I get a "Too many open files" error. >>>> 250 is probably OSX default max open file limit - but I don't understand >>>> why the 'with-input-from-process' doesn't appear to be closing its file >>>> handle? I also tried with 'open-input-process' and 'open-process' and >>>> manually calling 'close-input-port' but didn't help. Here's a small script >>>> that shows the exact same prob: >>>> >>>> (define (test-fn) >>>> >>>> (define (do-process) >>>> (with-input-from-process (list path: "pwd") read-all)) >>>> >>>> (let loop [(count 2000)] >>>> (if (> count 0) >>>> (begin >>>> (do-process) >>>> (loop (- count 1))) >>>> (println "Done")))) >>>> >>>> >>>> (test-fn) >>>> >>>> And the output: >>>> >>>> bigmac:iosTexConverter aking$ gsc -v >>>> v4.6.1 20110519175028 i386-apple-darwin10.8.0 "./configure >>>> /usr/local/Gambit-C/share/config.site /usr/local/Gambit-C/etc/config.site" >>>> >>>> bigmac:iosTexConverter aking$ gsi ./test.scm >>>> *** ERROR IN loop, "test.scm"@9.11 -- Too many open files >>>> (with-input-from-process '(path: "pwd") '#<procedure #2 read-all>) >>>> bigmac:iosTexConverter aking$ >>>> >>>> Running latest from the Gambit git repo and OSX 10.6.8. As far as I can >>>> tell, calling 'pwd' shouldn't be leaving around open file handles. I also >>>> checked the process-status, and it was 0. Any suggestions? >>>> >>>> _______________________________________________ >>>> Gambit-list mailing list >>>> Gambit-list(a)iro.umontreal.ca >>>> https://webmail.iro.umontreal.ca/mailman/listinfo/gambit-list >>>> >>>> >>> >> >

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New project
by Steve Graham 12 Sep '11

12 Sep '11

Although I have programmed for decades, I am new to Scheme/Gambit. I thought that I would use a project I've been contemplating as a help in learning the language. There is a website of scriptures which I wish to download. Some of the webpages, of course, are indices into books and then chapters. So I would need to follow the links until I got to the actual text, which I would then file into a database by volume, book, chapter and verse. I would appreciate any hints as to how to do this. I'm thinking I would need some help with downloading web pages, stripping HTML and saving to a database. TIA, Steve

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Gambit-list Septembre 2011