Re: [HACKERS] [PATCH] Improve geometric types

From: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
To: emre(at)hasegeli(dot)com
Cc: tgl(at)sss(dot)pgh(dot)pa(dot)us, alvherre(at)alvh(dot)no-ip(dot)org, robertmhaas(at)gmail(dot)com, a(dot)alekseev(at)postgrespro(dot)ru, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] [PATCH] Improve geometric types
Date: 2018-01-31 08:33:42
Message-ID: 20180131.173342.26333067.horiguchi.kyotaro@lab.ntt.co.jp
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At Wed, 31 Jan 2018 13:09:09 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote in <20180131(dot)130909(dot)210233873(dot)horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
> At Sun, 21 Jan 2018 21:59:19 +0100, Emre Hasegeli <emre(at)hasegeli(dot)com> wrote in <CAE2gYzxDYs5tcvc4uErsWaFTb3UTYS0ERt_fFyi-28Ldvs5d4A(at)mail(dot)gmail(dot)com>
> > New versions are attached including all changes we discussed.
>
> Thanks for the new version.
>
> # there's many changes from the previous version..
>
> About 0001 and 0002.
>
> 1."COPT=-DGEODEBUG make" complains as follows.
>
> | geo_ops.c:2445:62: error: invalid type argument of unary ‘*’ (have ‘float8 {aka double}’)
> | printf("dist_ppoly_internal- segment 0/n distance is %f\n", *result);
>
> 2. line_construct_pm has been renamed to line_construct. I
> noticed that the patch adds the second block for "(m == 0.0)"
> (from the ealier versions) but it seems to work exactly as the
> same to the "else" block. We need a comment about the reason
> for the seemingly redundant second block.
>
> 3. point_sl can return -0.0 and that is a thing that this patch
> intends to avoid. line_invsl has the same problem.
>
> 4. lseg_interpt_line is doing as follows.
>
> > if (FPeq(lseg->p[0].x, interpt.x) && FPeq(lseg->p[0].y, interpt.y))
> > *result = lseg->p[0];
> > else if (FPeq(lseg->p[1].x, interpt.x) && FPeq(lseg->p[1].y, interpt.y))
> > *result = lseg->p[1];
>
> I suppose we can use point_pt_point for this purpose.
>
> > if (point_eq_point(&lseg->p[0], &interpt))
> > *result = lseg->p[0];
> > else if (point_eq_point(&lseg->p[1], &interpt))
> > *result = lseg->p[1];
>
> However I'm not sure that adjusting the intersection to the
> tips of the segment is good or not. Adjusting onto the line
> can be better in another case. lseg_interpt_lseg, for
> instance, checks lseg_contain_point on the line parameter of
> lseg_interpt_line.
>

> # I'll be back later..

I've been back.

0003: This patch replaces "double" with float and bare arithmetic
and comparisons on double to special functions accompanied
with checking against abnormal values.

- Almost all of them are eliminated with a few safe exceptions.

- circle_recv(), circle_distance(), dist_pc(), dist_cpoint()
are using "< 0.0" comparison but it looks fine.

- pg_hypot is right to use bare arithmetics.

! circle_contain_pt() does the following comparison and it
seems to be out of our current policy.

point_dt(center, point) <= radius

I suppose this should use FPle.

FPle(point_dt(center, point), radius)

The same is true of circle_contain_pt(), pt_contained_circle .

# Sorry, that' all for today..

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center

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