Re: [HACKERS] More on 6.4 on DEC Alpha + Digital Unix 4.0d + DEC C compiler

"Thomas G. Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu> writes:
>> 1. Follow the ANSI spec and raise an error for exp() underflow.
>> The ERRNO path is already OK for this, but the other would have
>> to be made to read
>> if (!finite(*result) || *result == 0.0)
>> and we'd have to fix the expected regress output.

> OK, sounds good.

OK, I'll do something about it this weekend, unless someone beats me
to it.

>> BTW, while I was at it I took the time to figure out why the
>> pow() part of the test was failing for me (I was getting zeroes
>> instead of the expected "pow() result is out of range" error).
>> Turns out that depending on which HPUX math library version you
>> use, pow() might fail with EDOM rather than ERANGE for negative
>> inputs. I'll change the pow() code to check for either errno
>> when I get a chance.

> Hmm. Any chance of making that HP-specific? It would be a shame to make
> every platform test for two values on every calculation...

AFAICS, *any* error out of the pow() ought to be treated the same.
So what I was actually planning to do was

errno = 0;
result = pow(...);
if (errno != 0)
ELOG(...);

which is probably a cycle or two faster than what we have, since
testing against zero is usually a shade cheaper than comparison
to a nonzero constant.

Not that a cycle or three saved or wasted in a pow() function
evaluation is going to be significant, or even measurable ;-)

regards, tom lane