October 2007 - Gambit-list - mailman.iro.umontreal.ca

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

04 Apr '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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Please don't delete the .c file
by Bradley Lucier 07 Feb '08

07 Feb '08

Marc: I needed to debug a gsc-compiled file with gdb today, and it was fairly inconvenient that the .c file wasn't left around by compile- file in beta 21. I suggest that the .c file be left around for the various source tools that need it. Brad

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Leopard bug causing extremely slow parsing times
by James Long 10 Nov '07

10 Nov '07

I recently upgraded from OS X Tiger to Leopard and suddenly Gambit's "parsing" time has slowed to a crawl (I have confirmed this on another upgraded machine). I'm not sure if "parsing" is the correct term. But any time where Gambit reads a file and parses the code, gsc/gsi sits there and thrashes the CPU for some time linear to the size of the program. It takes 2.54s just to `include` a 300 line file. Execution speed is not affected. I tried recompiling Gambit but nothing changed. I know you can compile Gambit with --enable-debug and --enable-profile, but I'm not sure how to debug/profile the system. I think a `make check` does some timing checks, but I waited 2 hours for it to get past the first couple checks (because of the parsing bug) and then gave up. I wish I could give a better analysis of the problem, but after trying a couple methods of debugging (dtrace, testing different files, etc.), I'm not sure what the problem is. Anyone have Leopard and would be able to shed some light on this? Gambit-C v4.0.1, OS X 10.5 (Leopard) James

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shift/reset with *correct* dynamic environment
by James Long 31 Oct '07

31 Oct '07

Hello everyone, I have been studying delimited continuations recently. After being blissfully enlightened, I really wanted to have them in Gambit (with a *correct* dynamic environment). I wasn't sure if this was possible non-natively though (at least safely), because Gambit's dynamic environment is somewhat complex, and I have to be able to destructively manipulate the dynamic environment to make sure the delimited continuation truly has its own dynamic environment "slice". However, I figured out how to (hopefully safely) manipulate Gambit's dynamic environment, and I have a full implementation of shift/reset running in Gambit. This implementation is based off Oleg Kiselyov's work; his paper is here: http://okmij.org/ftp/Computation/dynamic-binding.html#DDBinding I am not sure of the performance implications of the Gambit version of shift/reset. I am unhappy with how much has to happen per reset or shift, but such is the cost of a non-native implementation. Unfortunately it goes against the grain of Gambit; after looking at some of Gambit's internals, Marc obviously has fine-tuned the code to be very efficient, and each reset or shift call is quite heavy compared to call/cc. Marc... what are thoughts on a native implementation of shift/reset? I included some tests which show that the dynamic environment does act the way we expect. If you are a zipped tar kind of guy: http://james.tech.coptix.com/files/shift-reset-gambit/shift-reset-gambit.ta… Or you just want the files: http://james.tech.coptix.com/files/shift-reset-gambit/shift-reset-fixed.scm http://james.tech.coptix.com/files/shift-reset-gambit/shift-reset-broken.scm http://james.tech.coptix.com/files/shift-reset-gambit/tests.scm "shift-reset-fixed.scm" contains the full shift/reset implementation. "shift-reset-broken.scm" contains a naive implementation with a broken dynamic environment. "tests.scm" has some tests to show how the dynamic env is fixed. Note that at the top you can include "shift-reset-broken.scm" instead of the fixed version to see how the dynamic env would normally be broken. James -- ; tests.scm (include "shift-reset-fixed.scm") (define var (make-parameter 5)) (define (displine) (disp "--------------------")) (define (disp . rest) (apply print (append rest '("\n")))) (define (dispv . rest) (print rest) (print "\n" (var) "\n")) (define (test f) (let ((k (f))) (k disp))) (define (test-parameterize f v1 v2) (parameterize ((var v1)) (let ((k (f v2))) (k dispv)))) (define (parameterize-no-shift v) (reset (parameterize ((var v)) (print "v: " (var)))) (disp ", v: " (var))) (define (parameterize-it-outside v) (parameterize ((var v)) (reset (dispv "inside reset") ((shift f (dispv "outside of reset") f) "inside reset again") (dispv "last time in reset")))) (define (parameterize-it-inside v) (reset (parameterize ((var v)) (dispv "inside reset") ((shift f (dispv "outside of reset") f) "inside reset again") (dispv "last time in reset")))) (define (wind-outside) (call/cc (lambda (k) (dynamic-wind (lambda () (disp "in winding")) (lambda () (k (reset ((shift f f) "in reset")))) (lambda () (disp "in unwinding")))))) (define (wind-inside) (reset (dynamic-wind (lambda () (disp "winding")) (lambda () ((shift f f) "inside dynamic-wind")) (lambda () (disp "unwinding"))))) (disp "Testing RAW RESET...") (parameterize-no-shift 20) (displine) (disp "Testing OUTSIDE PARAMETERIZE...") (test-parameterize parameterize-it-outside 10 11) (displine) (disp "Testing INSIDE PARAMETERIZE...") (test-parameterize parameterize-it-inside 10 11) (displine) (disp "Testing OUTSIDE WINDING...") (test wind-outside) (displine) (disp "Testing INSIDE WINDING...") (test wind-inside) ; The previous tests output what we expect: Testing RAW RESET... v: 20, v: 5 -------------------- Testing OUTSIDE PARAMETERIZE... inside reset 11 outside of reset 11 inside reset again 10 last time in reset 10 -------------------- Testing INSIDE PARAMETERIZE... inside reset 11 outside of reset 10 inside reset again 11 last time in reset 11 -------------------- Testing OUTSIDE WINDING... in winding in unwinding in reset -------------------- Testing INSIDE WINDING... winding unwinding winding inside dynamic-wind unwinding

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Can gambit-c fulfill this requirement?
by naruto canada 31 Oct '07

31 Oct '07

hi Can gambit-c fulfill this requirement? Let's say I have to implement some numerical library, and given some C headers files and description for what the library should do, and the C interface can not be changed for binary compatibility and ABI reason. The library is simply numerical and no IO or system call allowed (except malloc, free, and fprintf for debug). Can Hobbit generate C code that is suitable for linking and embeding in other project? There is no need for an interpreter. Thanks

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Experience integrating R6RS-style macros and modules into gambit
by Bradley Lucier 30 Oct '07

30 Oct '07

I'd like to hear people's experiences in integrating R6RS-style macros and modules into gambit, either with Abdulaziz Ghuloum's implementation http://www.cs.indiana.edu/~aghuloum/r6rs-libraries/ or Andre van Tonder's implementation http://www.het.brown.edu/people/andre/macros Brad

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Debugging define-macros
by Christopher Diggins 26 Oct '07

26 Oct '07

I was wondering if anyone could suggest a method of debugging "define-macro" expressions so that I can see what is actually being generated by the macro system (e.g. by preventing evaluation of the resulting macro, and printing it)? Otherwise I get a cryptic messages like "unbound unquote", and "ill-formed expression", but without any hints what is causing the grief in the generated code. Thanks, Christopher Diggins

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Tab completion
by Marc Feeley 17 Oct '07

17 Oct '07

I have added tab-completion to the builtin input line editor. When you press tab, the editor will extract the name preceding the cursor and search the symbol table for the lexicagraphically following symbol which will replace the original name. Pressing tab again will find the next symbol, and so on until the set of acceptable symbols is completely enumerated. Just get the latest changeset from the Gambit repository and run "make". Marc

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SRFI's for newbies
by Christopher Diggins 15 Oct '07

15 Oct '07

Hello, Warning: bumbling noob alert. I'm a new Gambit user, and new to Scheme, and I am somewhat familiar with SRFI's as being a suggested library for Scheme implementers but I can't find a list of which SRFI's are supported by Gambit. Scanning the documentation I found reference to the following SRFI's: SRFI-0 SRFI-6 SRFI-12 SRFI-18 SRFI-22 SRFI-33 SRFI-34 SRFI-27 SRFI-39 Is this a complete list? Would it be useful someone (perhaps myself) put this list up on the Wiki? What is the best way to get an unimplemented SRFI? For example, this one interests me: http://srfi.schemers.org/srfi-1/srfi-1.html . Should I just download the linked Scheme file from the SRFi file? Is there any particular reason why this or other SRFI's are not included in the distribution, or did I just overlook them? Sorry to ask so many questions, but it will help me get up to speed on the culture and eventually become a useful contributing member of this community. :-) Any help would be much appreciated. - Christopher Diggins

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working with ___arg* variables in c interface
by James Long 14 Oct '07

14 Oct '07

In a c-lambda, what are the types of the argument variables ___arg1, ___arg2, and so on? It seems like they are statically resolved to the types I passed in to the c-lambda, and everything happens that I expect to happen: (define %%addOne (c-lambda (int) int "___result=___arg1+1;")) (display (%%addOne 10)) This correctly prints out 11, and other various operations on pointers seemed to work too. For example, if 'ctx' is a structure with a 'id' field, and 'ctxp' is defined as (pointer ctx), the following function works fine: (define %%useCtx (c-lambda (ctxp) int "___result=(*___arg1).id;")) Basically, my question is when do I need to use ___CAST on the argument variables? Is it something I should be doing most of the time for safety, to suppress warnings or for some other reason? Or is it something done in a special case I haven't encountered yet? I've seen it done in other gambit FFI's and I'm wondering if the other was just paranoid or something (and if I should be).

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