Is there any value to, on a 64 bit machine, having 32 bit floats be immediate values to avoid boxing?
Robby On Saturday, October 2, 2010, Matthew Flatt <mfl...@cs.utah.edu> wrote: > Currently, every inexact real in Racket is represented by a 64-bit IEEE > floating-point number. > > There's an `--enable-float' configuration option that enables support > in Racket for 32-bit floating-point numbers. The use I see for 32-bit > arithmetic is to mimic some other program that uses 32-bit > floating-point arithmetic. (That was the original motivation, where I > was trying to perform Racket computations that mimicked C computations > in the drawing toolbox. I later settled on the solution of changing the > drawing toolbox to use `double' instead of `float' everywhere.) With > the current memory manager, I don't think there's any potential space > gain from using 32-bit floats instead of 64-bit floats. Is there any > other reason to use 32-bit floating point? > > The `--enable-float' option doesn't build at the moment, but the > immediate problems could be fixed easily. The bigger problem is the > interaction of 32-bit numbers and flonum-specific operations. As a > concept related to performance, we don't want "flonum" to include > multiple representations. It would make sense, though, to say that > "flonum" indicates a 64-bit floating-point number and is therefore more > specific than "inexact real". We would have to add `flonum?' and change > all guards on unsafe flonum-specific operations to use `flonum?' > instead of `inexact-real?'. Also, the distinction between inexact reals > and flonums would complicate Typed Racket's already-complex number > tower. > > Is it worth the effort to clean up this corner of the number system and > leave room for 32-bit floating-point (and maybe other representations > some day, as unlikely as that seems)? Or should we just declare > "inexact real" and "flonum" to be always 64-bit floating point once and > for all? > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
