Thread overview  


October 17, 2008 Re: CustomFloat  

 
Andrei Alexandrescu Wrote:
> I found myself in need for smaller and specialized floating point types, where I configure the exact configuration (sign, mantissa, exponent, bias). See http://en.wikipedia.org/wiki/Half_precision for a half precision number slated for inclusion in IEEE 754r.
>
> Would it be interesting to add a CustomFloat template to phobos? I'm thinking along the lines of:
>
> template CustomFloat!(bool sign, uint mantissa,
> uint exponent, uint bias)
> {
> ...
> }
>
> So halfprecision numbers are:
>
> alias CustomFloat!(true, 5, 10, 15) HalfFloat;
>
> There are quite a few details to kink out but this is definitely doable. Numbers like 24bit floating point and even 8bit floating point would be easy to support too. For now CustomFloat would be intended exclusively as a compact storage mechanism; only conversion to the standard floating points would be implemented. Later, maybe we can get to implement some operations natively at least on machines that support them in hardware. I wanted to gauge interest in the topic.
>
>
> Andrei
I've done some work on a set of decimal floating point numbers consistent with the new 754r decimal formats approved in June. Some of that work would be applicable here, I think.
It would probably make sense to add the decimal formats at the same time. Let me know if I can help.
Paul

October 17, 2008 Re: CustomFloat  

 
Posted in reply to Paul D. Anderson  Paul D. Anderson Wrote: > Andrei Alexandrescu Wrote: > > > I found myself in need for smaller and specialized floating point types, where I configure the exact configuration (sign, mantissa, exponent, bias). See http://en.wikipedia.org/wiki/Half_precision for a half precision number slated for inclusion in IEEE 754r. > > > > Would it be interesting to add a CustomFloat template to phobos? I'm thinking along the lines of: > > > > template CustomFloat!(bool sign, uint mantissa, > > uint exponent, uint bias) > > { > > ... > > } > > > > So halfprecision numbers are: > > > > alias CustomFloat!(true, 5, 10, 15) HalfFloat; > > > > There are quite a few details to kink out but this is definitely doable. Numbers like 24bit floating point and even 8bit floating point would be easy to support too. For now CustomFloat would be intended exclusively as a compact storage mechanism; only conversion to the standard floating points would be implemented. Later, maybe we can get to implement some operations natively at least on machines that support them in hardware. I wanted to gauge interest in the topic. > > > > > > Andrei > > I've done some work on a set of decimal floating point numbers consistent with the new 754r decimal formats approved in June. Some of that work would be applicable here, I think. > > It would probably make sense to add the decimal formats at the same time. Let me know if I can help. > > Paul > Here's a link to info regarding the decimal formats: http://speleotrove.com/decimal/ 
October 17, 2008 Re: CustomFloat  

 
Posted in reply to Paul D. Anderson  Paul D. Anderson wrote:
> Andrei Alexandrescu Wrote:
>
>> I found myself in need for smaller and specialized floating point
>> types, where I configure the exact configuration (sign, mantissa,
>> exponent, bias). See http://en.wikipedia.org/wiki/Half_precision
>> for a half precision number slated for inclusion in IEEE 754r.
>>
>> Would it be interesting to add a CustomFloat template to phobos?
>> I'm thinking along the lines of:
>>
>> template CustomFloat!(bool sign, uint mantissa, uint exponent, uint
>> bias) { ... }
>>
>> So halfprecision numbers are:
>>
>> alias CustomFloat!(true, 5, 10, 15) HalfFloat;
>>
>> There are quite a few details to kink out but this is definitely
>> doable. Numbers like 24bit floating point and even 8bit floating
>> point would be easy to support too. For now CustomFloat would be
>> intended exclusively as a compact storage mechanism; only
>> conversion to the standard floating points would be implemented.
>> Later, maybe we can get to implement some operations natively at
>> least on machines that support them in hardware. I wanted to gauge
>> interest in the topic.
>>
>>
>> Andrei
>
> I've done some work on a set of decimal floating point numbers
> consistent with the new 754r decimal formats approved in June. Some
> of that work would be applicable here, I think.
>
> It would probably make sense to add the decimal formats at the same
> time. Let me know if I can help.
Sounds interesting, and thanks for the offer. I'd be glad to add decimal types too, in case there's enough interest. I think monetary calculations can be helped, and what don't we do nowadays to help people involved in monetary calculations? :o)
Andrei

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