[gambit-list] Interactive 3D graphics with Gambit-C

Bradley Lucier lucier at math.purdue.edu
Tue Sep 23 16:14:28 EDT 2008


On Sep 23, 2008, at 2:32 PM, David St-Hilaire wrote:

>
> Alex Sandro Queiroz e Silva wrote:
>> Hallo,
>>
>>     I am thinking about doing some basic 3D graphics with Gambit-C.
>> Although I am sure code generated by Gambit-C is fast enough[1], I  
>> am a
>> bit worried about the garbage collector. What's the type of garbage
>> collector used by Gambit? If it kicks in during interactive  
>> rendering,
>> should I expect annoying pauses?
>>
>
> Unfortunately, yes you should expect such problems. If I'm correct,  
> gambit's gc
> is a regular stop & copy style collector, which stops the world at  
> each gc. I
> think that Marc has changing this to either a generationnal or  
> incremental gc,
> which would lead respectively to smaller collection pauses or  
> virtually none
> (but maybe with execution speed reduced?).
>
> Still, if you pre-allocate lots of space, gc shouldn't occur too  
> often and you
> can always force a gc with (##gc) at opportune moments.

GCs are often very short, on the order of milliseconds, for example on  
a 2.0GHz G5:

[descartes:~/Desktop] lucier% gsi
Gambit v4.2.8

 > (##gc-report-set! #t)
 > (define a (time (expt 3 10000000)))
*** GC: 1 ms, 692K alloc, 386K heap, 82.0K live (21% 65712+18208)
*** GC: 1 ms, 992K alloc, 386K heap, 88.0K live (23% 71920+18208)
*** GC: 1 ms, 1.19M alloc, 1.27M heap, 94.8K live (7% 55584+41536)
*** GC: 2 ms, 2.08M alloc, 2.22M heap, 163K live (7% 55456+111184)
*** GC: 2 ms, 3.22M alloc, 4.05M heap, 253K live (6% 55392+204064)
*** GC: 2 ms, 5.48M alloc, 6.86M heap, 435K live (6% 55328+389808)
*** GC: 4 ms, 9.98M alloc, 14.2M heap, 797K live (5% 55264+761280)
*** GC: 7 ms, 19.0M alloc, 27.2M heap, 1.49M live (5% 55200+1504224)
*** GC: 12 ms, 36.9M alloc, 54.0M heap, 2.90M live (5% 55136+2990128)
(time (expt 3 10000000))
     1165 ms real time
     1096 ms cpu time (936 user, 160 system)
     9 collections accounting for 33 ms real time (9 user, 23 system)
     71837896 bytes allocated
     no minor faults
     no major faults

I'd write the app without worrying about gc times, instrument it with  
##gc-report-set!, and then worry about gc's if they become a problem.

Brad


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