Why don't we switch to C like floating pointed arithmetic instead of automatic expansion to reals?

deadalnix via Digitalmars-d digitalmars-d at puremagic.com
Sun Aug 7 08:45:01 PDT 2016


On Saturday, 6 August 2016 at 09:35:32 UTC, Walter Bright wrote:
> On 8/6/2016 1:21 AM, Ilya Yaroshenko wrote:
>> We need 2 new pragmas with the same syntax as `pragma(inline, 
>> xxx)`:
>>
>> 1. `pragma(fusedMath)` allows fused mul-add, mul-sub, div-add, 
>> div-sub operations.
>> 2. `pragma(fastMath)` equivalents to [1]. This pragma can be 
>> used to allow
>> extended precision.
>
>
> The LDC fastmath bothers me a lot. It throws away proper NaN 
> and infinity handling, and throws away precision by allowing 
> reciprocal and algebraic transformations. As I've said before, 
> correctness should be first, not speed, and fastmath has 
> nothing to do with this thread.
>
>
> I don't know what the point of fusedMath is.

It's not as cut and dry. Sometime, processing faster mean you can 
process more data to begin with, and get a better result.



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