Folding constants for floats

[Carter Schonwald]

Oh I see the ticket.  Are you focusing on adding hex support to Double# and
Float# ? That would be splendid.  We currently don have a decent way of
writing nan, and the infinities.  That would be splendid.

On Monday, January 13, 2014, Carter Schonwald wrote:

> This is actually a bit more subtle than you'd think.  Are those constants
> precise and exact?  (There's certainly floating point code that exploits
> the cancellations in the floating point model) There's many floating point
> computations that can't be done with exact rational operations.  There's
> also certain aspects that are target dependent like operations having 80bit
> vs 64bit precision. (Ie using the old intel fp registers vs sse2 and newer)
>
> What's the ticket you're working on?
>
>
> Please be very cautious with floating point, any changes to the meaning
> that aren't communicated by the programs author could leave a haskeller
> numerical analyst scratching their head.  For example, when doing these
> floating point computations, what rounding modes will you use?
>
> On Monday, January 13, 2014, Kyle Van Berendonck wrote:
>
>> Hi,
>>
>> I'm cutting my teeth on some constant folding for floats in the cmm.
>>
>> I have a question regarding the ticket I'm tackling:
>>
>> Should floats be folded with infinite precision (and later truncated to
>> the platform float size) -- most useful/accurate, or folded with the
>> platform precision, i.e. double, losing accuracy but keeping consistent
>> behaviour with -O0 -- most "correct"?
>>
>> I would prefer the first case because it's *much* easier to implement
>> than the second, and it'll probably rot less.
>>
>> Regards.
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/ghc-devs/attachments/20140113/7eb44fd8/attachment.html>