Oh right! A generalized version of that strategy might work for Neil's program too.
On Saturday, August 18, 2012, Matthias Felleisen wrote: > > Vincent got TR to 'split' complex numbers, if that's what you mean by > 'wide enough' arguments, and he did so w/o changing R. So perhaps there is > a way to get the computation on floats and the tag for their meaning. > > > > On Aug 18, 2012, at 4:13 PM, Robby Findler wrote: > > One could, concievably, still do that without boxing/unblocking by passing > "wide enough" arguments. And it does seem like TR could help with that, but > IIUC the untyped portion of the compiler needs significant work to support > that before TR's knowledge of the program would help (But doing a better > job with structs is, iiuc, a long standing "something could be much better > here" type of thing.) > > On Saturday, August 18, 2012, Matthias Felleisen wrote: > >> >> But don't you need the 'tag' from the struct to distinguish .4 in p from >> .4 in 1-p? They may be the same number but they denote distinct ideas. -- >> Matthias >> ' >> >> >> On Aug 18, 2012, at 2:40 PM, Neil Toronto wrote: >> >> > Is TR's optimizer eventually going to unbox structs in the same way it >> unboxes rectangular flonums? >> > >> > I have a design choice right now: how to represent probabilities. >> Floats are good because of their speed, but because of floating-point >> limitations, *four different representations* are typically used. (For the >> curious: p, 1-p, log(p), and log(1-p).) I'd like to make functions that >> accept any one of these representations, denoted by this type: >> > >> > (define-type Probability >> > (U probability 1-probability log-probability log-1-probability)) >> > >> > The types are simply struct types that tag Float. >> > >> > Of course, manually boxing flonums ruins any chance of the compiler >> emitting code that keeps the flonums unboxed. If TR's optimizer unboxed >> structs, though, everything could be speedy. >> > >> > FWIW, by "eventually," I mean "within the next n years", where "n" is a >> smallish number. >> > >> > Neil ⊥ >> > _________________________ >> > Racket Developers list: >> > http://lists.racket-lang.org/dev >> >> >
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