| From: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
|---|---|
| To: | Vik Fearing <vik(dot)fearing(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Stephen Frost <sfrost(at)snowman(dot)net>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Chapman Flack <chap(at)anastigmatix(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Greatest Common Divisor |
| Date: | 2020-01-03 19:14:13 |
| Message-ID: | alpine.DEB.2.21.2001032010470.12030@pseudo |
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| Lists: | pgsql-hackers |
Bonsoir Vik,
+int4gcd_internal(int32 arg1, int32 arg2)
+{
+ int32 swap;
+
+ /*
+ * Put the greater value in arg1.
+ * This would happen automatically in the loop below, but avoids an
+ * expensive modulo simulation on some architectures.
+ */
+ if (arg1 < arg2)
+ {
+ swap = arg1;
+ arg1 = arg2;
+ arg2 = swap;
+ }
The point of swapping is to a void possibly expensive modulo, but this
should be done on absolute values, otherwise it may not achieve its
purpose as stated by the comment?
> gcd() is now strictly positive, so INT_MIN is no longer a valid result.
Ok.
I'm unsure about gcd(INT_MIN, 0) should error. Possibly 0 would be
nicer?
--
Fabien.
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