• Paul D. Anderson <paul.d.removethis.anderson comcast.andthis.net> Oct 17 2008
• Paul D. Anderson <paul.d.removethis.anderson comcast.andthis.net> Oct 17 2008
• Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> Oct 17 2008

Paul D. Anderson <paul.d.removethis.anderson comcast.andthis.net> writes:

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 half-precision 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 24-bit floating point and even 8-bit 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

Paul D. Anderson <paul.d.removethis.anderson comcast.andthis.net> writes:

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 half-precision 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 24-bit floating point and even 8-bit 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/

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

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 half-precision 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 24-bit floating point and even 8-bit 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