Re: Making Lemonade (Floating-point format changes)

John Savard <quadibloc@servername.invalid> schrieb:

I have instead defined a 256-bit format for floats which does not have
a hidden first bit, which looks like the old temporary reals, except
that the exponent field is one bit wider.

Why not the IEEE binary256 (interchange) format?

https://en.wikipedia.org/wiki/Octuple-precision_floating-point_format

[...]

I've defined how the 256-bit internal format floats
can be doubled up to make a 512-bit float.

Such floating point formats have very strange properties.
For example, try defining epsilon so that 1.0+epsilon is the
smallest number larger than 1.0...

IBM just spent a lot of effort to move away from that for POWER.

I'm not really sure such floating-pont precision is useful, but I do
remember some people telling me that higher float precision is indeed
something to be desired. Well, the IEEE 754 standard has forced my
hand.

How so?