Re: Parsing timestamps?

On 10/07/2025 8:10 am, Paul Rubin wrote:

dxf <dxforth@gmail.com> writes:

As for SSE2 it wouldn't exist if industry didn't consider
double-precision adequate.

 
SSE2 is/was first and foremost a vectorizing extension, and it has been
superseded quite a few times, indicating it was never all that
adequate.  I don't know whether any of its successors support extended
precision though.
 
W. Kahan was a big believer in extended precision (that's why the 8087
had it from the start).  I believes IEEE specifies both 80 bit and 128
bit formats in addition to 64 bit.  The RISC-V spec includes encodings
for 128 bit IEEE but I don't know if any RISC-V hardware actually
implements it.  I think there are some IBM mainframe CPUs that have it.

I suspect IEEE simply standardized what had become common practice among
implementers.  By using 80 bits /internally/ Intel went a long way to
achieving IEEE's spec for double precision.

What little I know about SSE2 it's not as well thought out or organized
as Intel's original effort.  E.g. doing something as simple as changing
sign of an fp number is a pain when NANs are factored in.  With the x87,
Intel 'got it right the first time'.  Except for the stack size and
efforts to fix it.