Re: Making Lemonade (Floating-point format changes)

BGB <cr88192@gmail.com> schrieb:

Granted, they are not necessarily the option one would go if they wanted
"cheapest possible FPU that is still good enough to be usable".
>
Though, the point at which an FPU manages to suck badly enough that one
needs to resort to software emulation to make software work, is probably
a lower limit.
>
>
Luckily, "uses 754 formats, but with aggressive cost cutting" can be
"good enough", and so long as they more-or-less deliver a full width
mantissa, and can exactly compute exact-value calculations, most
software is generally going to work.

This will require extensive testing and possibly modification for
a lot of software ported to such a system.  This will drive up
the total cost, presumably far more than any hardware savings.

But OTOH, if 1.0+2.0 gives 2.999999, that is, not good enough, so there
is a lower limit here.

An example of a more interesting question is

  if (a >= 0.) {
    if (b >= 0) {
      if (a + b < a) {
        printf("We should never get here!\n);
abort();
      }
    }
  }