[racket-dev] What are single flonums good for?

TR doesn't support them anyways because there are only typed f64
vectors and not typed f32 vectors.

Jay

On Fri, Sep 14, 2012 at 11:28 AM, Robby Findler
<robby at eecs.northwestern.edu> wrote:
> As far as I can tell, if this pollutes TR programs in any interesting
> way, then it would be a cause for concern.
>
> Robby
>
> On Fri, Sep 14, 2012 at 12:21 PM, John Clements
> <clements at brinckerhoff.org> wrote:
>>
>> On Sep 12, 2012, at 1:03 PM, Jay McCarthy wrote:
>>
>>> On Wed, Sep 12, 2012 at 8:31 AM, Neil Toronto <neil.toronto at gmail.com> wrote:
>>>> Compatibility with C code? Why not have the FFI convert them?
>>>>
>>>> Save space? I can see that. It won't help much if they're sent to math
>>>> library functions, though. Those will convert them to flonums and usually
>>>> box the converted values.
>>>
>>> I think these are big deals with respect to libraries that you deliver
>>> large float matrices to where you want to efficiently store a big
>>> f32vector rather than an f64vector. Examples of this include OpenGL
>>> where vector coordinates, colors, etc are typically floats and not
>>> doubles.
>>
>> Jay's concern is the same as mine; there are situations (getting rarer) where a huge c-style array of f32s is the only way to interact with a library. For instance, in the extremely popular "JACK" library (Golly, I wish it worked on windows…), "all audio data is represented as 32-bit floating point values" (from their web page).
>>
>> I haven't followed the conversation closely enough to understand the ramifications of the proposed change, though; my guess is that the ffi can still address such arrays, it's just that computing with these values will require coercion. I could be okay with that; based on my understanding of the IEEE floating-point spec, such a translation could be pretty fast; 32bit -> 64bit looks like it would just be adding zeros, and 32bit to 64bit would require checking for exponent overflow; either way, this sounds like something that might be done on-chip by modern processors, and in fact might *already* be taking place in floating point 32-bit operations. (Anyone know whether Intel chips internally represent 32-bit floats as 64-bit ones?)
>>
>> John
>>
>>
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-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://faculty.cs.byu.edu/~jay

"The glory of God is Intelligence" - D&C 93