On 09/26/2018 06:45 PM, Tom Lane wrote:
> Tomas Vondra <tomas.von...@2ndquadrant.com> writes:
>> Pushed. Now let's wait for the buildfarm to complain ...
>
> gaur's not happy, but rather surprisingly, it looks like we're
> mostly OK elsewhere. Do you need me to trace down exactly what's
> going wrong on gaur?
>
Hmmm, interesting. It seems both failures happen in the chunk that
multiplies paths with points, i.e. essentially point_mul_point. So it
seems most platforms end up with
(0,0) * (-3,4) = (-0, 0)
while gaur apparently thinks it's (0,0). And indeed, that's what the
attached trivial program does - I'd bet if you run it on gaur, it'll
print 0.000000, not -0.000000.
Or you could just try doing
select '(0,0)'::point * '(-3,4)'::point;
If this is what's going on, I'd say the best solution is to make it
produce (0,0) everywhere, so that we don't expect -0.0 anywhere.
We could do that either by adding the == 0.0 check to yet another place,
or to point_construct() directly. Adding it to point_construct() means
we'll pay the price always, but I guess there are few paths where we
know we don't need it. And if we add it to many places it's likely about
as expensive as adding it to point_construct.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
#include <stdio.h>
int main()
{
double x1 = 0.0,
x2 = -3,
y1 = 0.0,
y2 = 4;
printf("%+f\n", (x1 * x2) - (y1 * y2));
return 0;
}
