🚀 go-pugleaf

"GerardS" <GerardS@PrairieTech.Net> writes:

> | Richard Maine wrote:
> |> Ron Shepard wrote:
> |> Are the exponents converted automatically with these instructions?
> |> If they aren't, then it seems odd to be able to convert between a
> |> double precision floating point value to a single precision value
> |> just by loading the value into a register.
> |
> | Add usual caveat about my memory, but the exponents don't *NEED*
> | converting.  I recall thinking it sort of strange the first time I saw
> | floating point formats where the exponents weren't the same for single
> | and double.  I've subsequently gotten used to it.  Sounds to me like
> | you are so used to it that you didn't think of the other possibility.  :-)
> 
> What if the number isn't normalized ? ___________________________Gerard S.

Why would it make any difference?  It doesn't that I know of.  Do you
have something in specific in mind?

Yes, numbers that are not normalized are prone to lose precision if
you don't normalize them before operations.  In particular, if you
convert a nonnormalized double to a single, you'll presumably get
a nonnormalized single, which will have worse precision than the
horrid IBM single format does anyway.

If one goes around doing operations on nonnormalized data, you are
likely to lose precision in general.  Nothing unique to
single-double conversion here that I see.

Again, I ackowledge that my memory may be confusing systems.  I
certainly recall (with much pain) the IBM single precision floating
point.  I get a little hazy about the details of the machine
instruction set, though.  I did once do some BAL coding - even took a
formal course in it, but it's been a long time (nearly 30 years) and I
never did a lot of it.

-- 
Richard Maine                       |  Good judgment comes from experience;
email: my first.last at org.domain  |  experience comes from bad judgment.
org: nasa, domain: gov              |        -- Mark Twain