Accuracy of floating point calculations

[Robert M. Münch]

On 2019-10-30 15:12:29 +0000, H. S. Teoh said:

> It wasn't a wrong *decision* per se, but a wrong *prediction* of where
> the industry would be headed.

Fair point...

> Walter was expecting that people would move towards higher precision, 
> but what with SSE2 and other such trends, and the general neglect of 
> x87 in hardware developments, it appears that people have been moving 
> towards 64-bit doubles rather than 80-bit extended.

Yes, which is wondering me as well... but all the AI stuff seems to 
dominate the game and follow the hype is still a frequently used 
management strategy.

> Though TBH, my opinion is that it's not so much neglecting higher
> precision, but a general sentiment of the recent years towards
> standardization, i.e., to be IEEE-compliant (64-bit floating point)
> rather than work with a non-standard format (80-bit x87 reals).

I see it more of a "let's sell what people want". The CPU vendors don't 
seem able to market higher precision. Better implement a 
highly-specific and exploding command-set...

> Do you mean *simulated* 128-bit reals (e.g. with a pair of 64-bit
> doubles), or do you mean actual IEEE 128-bit reals?

Simulated, because HW support is lacking on X86. And PPC is not that 
mainstream. I exect Apple to move to ARM, but never heard about 128-Bit 
support for ARM.

> I'm still longing for 128-bit reals (i.e., actual IEEE 128-bit format)
> to show up in x86, but I'm not holding my breath.

Me too.

> In the meantime, I've been looking into arbitrary-precision float 
> libraries like libgmp instead. It's software-simulated, and therefore 
> slower, but for certain applications where I want very high precision, 
> it's the currently the only option.

Yes, but it's way too slow for our product.

Maybe one day we need to deliver an FPGA based co-processor PCI card 
that can run 128-Bit based calculations... but that will be a pretty 
hard way to go.

-- 
Robert M. Münch
http://www.saphirion.com
smarter | better | faster