On Nov 11, 2012, at 10:36 AM, Sam Tobin-Hochstadt wrote: > On Sat, Nov 10, 2012 at 11:07 PM, John Clements > <cleme...@brinckerhoff.org> wrote: >> >> On Nov 10, 2012, at 7:29 AM, Robby Findler wrote: >> >>> If you're calling from Racket to TR then you have the contract >>> checking and probably the floats flowing thru there need boxing. >> >> If I understand you correctly, the contract checking would just be "is this >> a float?" which I imagine wouldn't require additional memory. Certainly the >> return value would have to be boxed, and that would definitely be eight >> bytes, I'm guessing. > > There's also the allocation overhead involved in wrapping the > function, plus probably lots of other places where unboxing is > inhibited.
When you say "wrapping the function", it sounds like a once-per execution
thing, not a once-per-call thing.
Okay, while I've got you, my recollection is that you wrote a bunch of the
decompiler. so, in this decompiled definition:
(define-values
(_comb1)
(lambda (arg0-117)
'#(comb1
#<path:/Users/clements/clements/teaching/csc123-fa12/examples/compiled/reverb-typed.rkt>
58
0
1468
309
#f)
'(flags: preserves-marks single-result)
'(captures: #%modvars (_d1 _g21 _v1 _m1 _c1))
(let ((local118
(#%as-flonum
(#%flonum
unsafe-fl+
(#%flonum flvector-ref _v1 (#%checked _c1))
(#%flonum unsafe-fl* '0.46 (#%checked _m1))))))
(let ((local125
(#%flonum
unsafe-fl+
(#%flonum unsafe-fl* _g21 (#%from-flonum local118))
arg0-117)))
(begin
(#%flonum flvector-set! _v1 (#%checked _c1) local125)
(let ((local133 (#%in add1 (#%checked _c1))))
(begin
(set! (#%checked _c1) (if (#%in <= _d1 local133) '0 local133))
(set! (#%checked _m1) (#%from-flonum local118))
local125)))))))
... it looks like most of the places where I want to avoid unboxing are already
correctly marked with (#%from-flonum...), which the documentation suggests will
allow unboxing. It looks to me like the uses of #%checked could be avoided by
some kind of type cleverness, though it's not clear to me whether uses of
#%checked are going to cause allocation, or just consume CPU time.
Also; can I assume from the separate presentation of 'comb1'--and the fact that
this code doesn't appear anywhere else in the decompiled file--that it hasn't
been inlined?
>
>>>
>>> Can you put the loop itself into TR?
>>
>> Sadly, no; the loops themselves are written by students. Or, more
>> specifically, written by students as a "network" form that expands into a
>> function that's called in a loop. I think that expanding into TR would be
>> incredibly hard to get right.
>
> I'm not sure why this would be. Is the code students write unrestricted?
Pretty much, yes. So, for instance, a student might write:
(signal-play
(network ()
[s ((looper song2))]
[ctr ((loop-ctr 0 1))]
[on? (toggle ctr)]
[out (reverb s)]))
where the signals take on float, boolean, or any kind of value. This expands
into something containing this "inner loop" procedure:
(lambda ()
(define s (n1))
(define ctr (n2))
(define on? (toggle ctr))
(define out (reverb s))
(set! saved-s s)
(set! saved-ctr ctr)
(set! saved-on? on?)
(set! saved-out out)
out)
It would be pretty hard to assign types any tighter than "any" to these rhs
expressions.
Thanks in advance for any advice!
John
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