On 14/04/2014 10:44 AM, Francesco Cattoglio wrote:
This would make sense, at least partially, if hardware supporting the
ieee was non-existant, but apparently hardware support for the decimal64
standard is already here!
Being a numerical analyst I can say I'm extremely interested when
someone comes up with new interesting ideas, but as far as I can tell we
still need to go down a long road before finding something better than
good old floats. And I really think that one should stick to the
standards, as long as the standard is good enough.
On a side note, I think that support for decimal64 might be something
nice to have in the D language, because apparently that one is the most
used floating point type in the economic sectors.
I did a little research, you are right, IBM has implemented the IEEE
decimal floats in their Power6 and z9 chips (since 2007), and Sparc64
chips have it too (since 2012). But the amount of silicon required to
create these decimal FPUs is significantly greater than for binary FPUs
(as the format is essentially a dense form of BCD) and this makes it
very unlikely that they will ever make their way into desktop or mobile
processors.
The Dec64 decimal float is not a form of BCD, which is part of the
reason why it can be emulated in software in a significantly more
efficient way than the IEEE standard. While no hardware design exists,
this would suggest that it would require less silicon, giving a greater
chance that it will get into non-mainframe hardware.
A while ago there was a proposal for a new decimal float format to be
included in ECMAScript 4 but the resources for that proposal seem to
have been purged ()I've only found a few broken links. But as Doug
Crockford (who at least wrote the dec64 reference implementation if not
conceived the whole design) is on the TC39 committee that works on the
standards for ECMAScript, I assume that it is related to that proposal
and might even become a part of ECMAscript standard in the future.
Doug is a competent and respected programmer and speaker (among other
things, he "discovered" JSON), and I believe that he would not have
begun this project if there were not a compelling reason to do so. I
hope that I am not misrepresenting him any way.
I will endeavour to port the reference implementation solo as it will
undoubtedly be educational, and also to find more evidence that the
effort is worth my time! I'll gladly share both.
A...
