Gambit-list Décembre 2004

gambit-list@iro.umontreal.ca

11 participants
16 discussions

Re: C pointers
by Eduardo Cavazos 31 Déc '04

31 Déc '04

Hello Thomas, Below you provide the example function 'inc_int' and ask what you should pass to it. You should pass it a pointer to an int of course. :-) And where do you get such an object? You can make one with another c-lambda based function. For example: (define make-int-box (c-lambda () int* "___result = malloc(sizeof( int ));")) So now you can do: (define i (make-int-box)) (inc_int i) There is a problem... the int box doesn't contain anything to increment. So we should have a way to set the value inside the box. We also need a way to access the contents of the box. These functions do these: (define set-int-box (c-lambda (int* int) void "*___arg1 = ___arg2;")) (define val-int-box (c-lambda (int*) int "___result = *___arg1;")) That should get you started. The atomic code I announced a few days ago contains a macro called 'c-box' that works like this: (c-box int) Now you can do this: ;; Make a new int box (define i (new-int-box)) ;; Set the value of the box: [i val: 0] ;; Call your inc_int to increment the value in the box (inc_int [i box:]) ;; Print the new value: [i val:] Happy Hacking Ed Cavazos On 31 Dec 2004 17:39:20 +0100, Thomas Hafner <thomas(a)hafner.nl.eu.org> wrote: > Some given C functions receive pointers and manipulate the memory > where the pointers are pointing to. How should my c-lamda expression > look like to mach that requirement? > > Here's a simple example (not real, but to show my problem). If the > given C Funktion looks like that: > void inc_int(int *pI) > { > (*pI)++; > } > > Is it then Ok to use it from Gambit 4.0 beta 11 like follows? > (define inc-int > (c-lambda ((pointer int)) > void > "inc_int")) > > If yes: what can I pass to inc-int? How to express the Scheme > equivalent to the C pointer? > > Otherwise: how should my Scheme procedure definition look like? Of > course the example above is a very simple one. A good solution should > also work with more complicated C functions, e.g. of type > int () (int *, char **). > > Regards > Thomas Hafner > > _______________________________________________ > Gambit-list mailing list > Gambit-list(a)iro.umontreal.ca > http://mailman.iro.umontreal.ca/mailman/listinfo/gambit-list >

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C pointers
by Thomas Hafner 31 Déc '04

31 Déc '04

Some given C functions receive pointers and manipulate the memory where the pointers are pointing to. How should my c-lamda expression look like to mach that requirement? Here's a simple example (not real, but to show my problem). If the given C Funktion looks like that: void inc_int(int *pI) { (*pI)++; } Is it then Ok to use it from Gambit 4.0 beta 11 like follows? (define inc-int (c-lambda ((pointer int)) void "inc_int")) If yes: what can I pass to inc-int? How to express the Scheme equivalent to the C pointer? Otherwise: how should my Scheme procedure definition look like? Of course the example above is a very simple one. A good solution should also work with more complicated C functions, e.g. of type int () (int *, char **). Regards Thomas Hafner

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Announce: atomic
by Eduardo Cavazos 28 Déc '04

28 Déc '04

ATOMIC 0.1.3 http://proteus.freeshell.org/atomic/atomic-0.1.3.tar.gz A collection of code for the Gambit Scheme System. atomic.scm A base library for the rest of the system object.scm * A simple object system * It's relatively concise when compared to traditional Scheme record systems * Example: (class <point> x y) (def p0 (new <point> x: 4 y: 5)) [p0 x:] ;; Getting a slot [p0 x: 10] ;; Setting a slot Xlib * X Lib bindings * Based on the code that comes with the Gambit 4.0 beta distributions * The function and macro names are the same as the C library counterparts. she * A very simple UNIX shell * Supports some basic /bin/sh features like pipes * Readline support * Shell functions are written in Scheme winman * A simple window manager used to test the Xlib bindings and to explore window manager hacking * A REPL like window can be opened to interact with the system This release of Atomic is for Gambit 3.0. It will not work under 4.0. Atomic is in the early stages but is useful. I use the window manager and am close to using the shell full time. Right now it is a testbed for ideas. I welcome any mail regarding the system. Ed Cavazos

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Re: [gambit-list] homogeneous vector performance
by Bradley Lucier 13 Déc '04

13 Déc '04

On Dec 11, 2004, at 4:14 PM, dev null wrote: > I've been playing around with implementations of simple algorithms in > C and gambit scheme, trying to get some idea of the latter's > usefulness for some of my scientific computing. My experience is that once you have problems that don't fit in first or second-level cache, the speed is the same for scientific computing. See http://www.math.purdue.edu/~lucier/615/software/ Also, if you're using gcc, the following options may improve the performance of code generated by Gambit: -O1 -fno-math-errno -fschedule-insns2 -fno-trapping-math -fno-strict-aliasing -fomit-frame-pointer (These options are chosen by configure when building gambit.) You may need the -fno-strict-aliasing for correctness of the compiled code. In my experience code compiled with -O2 goes slower. Brad

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CPS and state machines
by Joel Reymont 13 Déc '04

13 Déc '04

Would anyone have an example of implementing a state machine in continuation passing style (CPS)? I'm looking for a simple example although it does not have to be. I'd like to implement a state machine for a game lobby where on receipt of event-1 I would send game summaries, on event-2 player summaries, etc. I will then build on this example to implement a poker logic state machine. In the game logic fsm there are events like player-joined and player-left and where the game would end when there are not enough players or begin when enough players joined and where it would otherwise state in the same state. Thanks, Joel -- OpenPoker: The Linux of poker software http://wagerlabs.com/forums

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Gambit 4.0b11 and ICC 8.1
by Sven.Hartrumpf＠fernuni-hagen.de 12 Déc '04

12 Déc '04

Hi all. Has anybody compiled Gambit with ICC instead of gcc? My build process ends like this: _kernel.c(16881): remark #1418: external definition with no prior declaration ___BEGIN_MOD2 ^ _kernel.c(16881): remark #869: parameter "___gs" was never referenced^M ___BEGIN_MOD2 ^ icc: error: Fatal error in /opt/intel_cc_80/bin/mcpcom, terminated by segmentation violation compilation aborted for _kernel.c (code 1) make[1]: *** [_kernel.o] Error 1 make[1]: Leaving directory `tmp/gambc40b11/lib' make: *** [all] Error 1 Full typescript at ki220.fernuni-hagen.de/hartrumpf/gambit/ Greetings Sven

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homogeneous vector performance
by dev null 11 Déc '04

11 Déc '04

Hi, I've been playing around with implementations of simple algorithms in C and gambit scheme, trying to get some idea of the latter's usefulness for some of my scientific computing. One of the things I did was code `insertion sort' in both languages: ------------------------------------------------------------------ #include <stdio.h> void isort(int a[], int len) { int i; for (i=1; i < len; i++) { int j; int key = a[i]; for (j=i-1; (j >= 0) && (a[j] > key); j--) { a[j+1] = a[j]; } a[j+1] = key; } } int main(void) { int i; int len = 100000; int * a = (int *) malloc(sizeof(int) * len); for (i=0; i < len; i++) { a[i] = len - i; } isort(a, len); free(a); return 0; } ------------------------------------------------------------- (declare (standard-bindings) (block) (not safe) (fixnum)) (define isort! (lambda (a) (let ((len (vector-length a))) (do ((i 1 (+ i 1))) ((>= i len) a) (let ((key (vector-ref a i))) (vector-set! a (do ((j (- i 1) (- j 1))) ((or (< j 0) (< (vector-ref a j) key)) (+ j 1)) (vector-set! a (+ j 1) (vector-ref a j))) key)))))) (define v (make-vector 100000)) (do ((i 0 (+ i 1)) (len (vector-length v))) ((>= i len)) (vector-set! v i (- len i))) (isort! v) --------------------------------------------------------------------------- For 100_000 elements, my laptop executes the C version in 11 secs and the scheme code in 20 secs. Since the two codes are written at similar abstractions levels, ideally I would like the scheme code to do a little better. Thinking that part of the problem might be the use of an overly-generic scheme vector vs a simple C integer array, I rewrote the scheme version using u32vector functions (just replacing vector-* above with u32vector-*). The result was not what I expected. I was able to sort a 10_000 element u32vector in 26 seconds, but the 100_000 element problem ran for 38 minutes before I got bored with it and killed it. Two questions: 1) Is it possible to make the scheme code run any faster? 2) Does anyone have an idea why the u32vector-based version runs so slow? Thanks very much, Ben

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A small bug report
by Eric Merritt 09 Déc '04

09 Déc '04

Marc, I came across this bug by accident. Its not important to me in any way but I thought you should know about at. It seems that any attempt to apply ##symbol-hash to a symbol composed of numbers, ie (##symbol-hash '33) of (##symbol-hash '5321) causes gsi to segfault. This may or may not have wider implications. -- I'm a programmer, I don't have to spell correctly; I just have to spell consistently

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Calling a Gambit function from C++
by Joel Reymont 08 Déc '04

08 Déc '04

Are there any examples of integrating Gambit with C++? I'm looking for an example of how I should call a Scheme function within Gambit. I understand that all the Scheme code would be compiled but where would I find the "entry point" into Gambit and how would I call my Scheme function? Thanks, Joel -- OpenPoker: The Linux of poker software http://wagerlabs.com/forums

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Pushing events between C++ and Scheme + timers
by Joel Reymont 08 Déc '04

08 Déc '04

Fellow Schemers, I have 3 event-related needs: 1. I need to push events from C++ to Scheme 2. I need to push events from Scheme to C++ 3. I need to setup timers within Scheme that would also generate events I could have C++ call a Scheme function and have the Scheme function return data. This would cover 1 and 2 except I would need to pass a list of events back into Scheme. Sometimes I need to pass events from Scheme to C++ this could be one event or it could be a few. Last but not least, I need to generate an event (i.e. do something) when a timer expires. All my processing could be done in a blocking fashion if it weren't for timers. For example, I would set up a timer while waiting for player action and if the timer expired I would assume that the player is dead and fold his cards (this is poker) and force him to leave the game (remove him). I would also set up a timer after enough players gathered for a game, just to wait and see if someone else would join. If there's still enough players after the timer expires then I would start the game. Otherwise I would go back to waiting for players. My main loop MUST run in C++ as for my server I'm using a C++ networking library and for my GUI client I'm using SDL which has its own event loop as well. Something I could do is set up two queues (lists?) in Scheme, one for incoming events and one for outgoing. My scheme code would then run in some sort of a thread, polling the incoming queue and posting events to the outgoing queue. C++ would poll the outgoing queue and post events to the incoming queue via a Scheme call. Writing Scheme bindings for the networking library and for SDL could be another option but I'd rather try to set up a thin C++ to Scheme interface layer first as it would let me focus on the application logic. Any suggestions? Thanks in advance, Joel -- OpenPoker: The Linux of poker software http://wagerlabs.com/forums

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Gambit-list Décembre 2004