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From: Kevin Ryde <user42@zip.com.au>
Subject: Re: GMP code committed -- watch for bugs.
Date: Mon, 07 Apr 2003 08:50:42 +1000	[thread overview]
Message-ID: <87wui76y0t.fsf@zip.com.au> (raw)
In-Reply-To: 87he9dhoxh.fsf@raven.i.defaultvalue.org

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Rob Browning <rlb@defaultvalue.org> writes:
>
> There may well be bugs

A small one in (gcd n 0), test and possible fix below.  The result
should of course be abs(n) but mpz_gcd_ui can't return that if it
doesn't fit a ulong.

> where
> special casing with GMP operations could help, but it'll probably take
> some good benchmarking to know for sure.

ash (mentioned in the comments) would definitely benefit from the mpz
2exp functions.

In gcd, it'd be nice for the inum/bignum case to share code with the
bignum/inum case, like lcm does.


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--- numbers.test.~1.16.~	2003-03-26 09:11:21.000000000 +1000
+++ numbers.test	2003-04-06 15:09:42.000000000 +1000
@@ -788,6 +788,11 @@
     (pass-if "n = fixnum-min - 1"
       (eqv? (- (- fixnum-min 1)) (gcd 0 (- fixnum-min 1)))))
 
+  (with-test-prefix "(n 0)"
+
+    (pass-if "n = 2^128 * fixnum-max"
+      (eqv? (ash fixnum-max 128) (gcd (ash fixnum-max 128) 0))))
+
   (with-test-prefix "(1 n)"
 
     (pass-if "n = 0"

[-- Attachment #3: numbers.c.gcd-n-0.diff --]
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Index: numbers.c
===================================================================
RCS file: /cvsroot/guile/guile/guile-core/libguile/numbers.c,v
retrieving revision 1.177
diff -u -u -F^[[:alpha:]$_] -r1.177 numbers.c
--- numbers.c	5 Apr 2003 19:10:22 -0000	1.177
+++ numbers.c	6 Apr 2003 22:48:02 -0000
@@ -708,6 +708,8 @@
         {
           unsigned long result;
           long yy = SCM_INUM (y);
+          if (yy == 0)
+            return scm_abs (x);
           if (yy < 0) yy = -yy;
           result = mpz_gcd_ui (NULL, SCM_I_BIG_MPZ (x), yy);
           scm_remember_upto_here_1 (x);

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  parent reply	other threads:[~2003-04-06 22:50 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-04-04 22:34 GMP code committed -- watch for bugs Rob Browning
2003-04-05 12:24 ` Marius Vollmer
2003-04-05 21:51 ` Mikael Djurfeldt
2003-04-05 22:26   ` Rob Browning
2003-04-06  7:41     ` Mikael Djurfeldt
2003-04-06  9:16   ` Mikael Djurfeldt
2003-04-06 18:43     ` Rob Browning
2003-04-06 19:12       ` Mikael Djurfeldt
2003-04-06 20:09         ` Rob Browning
2003-04-06 20:25     ` Rob Browning
2003-04-06  9:23 ` Mikael Djurfeldt
2003-04-06 20:15   ` Rob Browning
2003-04-06 22:50 ` Kevin Ryde [this message]
2003-05-10  0:22   ` GMP code committed -- watch for bugs ... gcd n 0 Kevin Ryde
2003-04-23 22:40 ` GMP code committed -- watch for bugs Kevin Ryde

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