| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, emre(at)hasegeli(dot)com, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: [PATCH] Improve geometric types |
| Date: | 2018-09-27 17:21:30 |
| Message-ID: | 20180927172130.jszubilgi7fy6pjs@alvherre.pgsql |
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| Lists: | pgsql-hackers |
If you look at the differing results carefully, there's this one:
*** 3249,3255 ****
! [(0,0),(3,0),(4,5),(1,6)] | (-5,-12) | [(0,-0),(-15,-36),(40,-73),(67,-42)]
--- 3249,3255 ----
! [(0,0),(3,0),(4,5),(1,6)] | (-5,-12) | [(0,0),(-15,-36),(40,-73),(67,-42)]
(Third column is first multiplied by second).
I wonder why the expected file has a -0 only in the second position and
not both first and second. These are both positive zeroes being
multiplied by a negative number. Why is 0 * -12 = -0 yet 0 * -5 = 0?
What is going on? Is the sign suppressed for negative zeros only in the
first coordinate? I suppose this is just a side effect of how
float8_mi, _pl, _mul work (in point_mul_point).
Anyway maybe your test case should use more of the float8 op
combinations in order to show the difference.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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