[Jprogramming] Oddities with /:

[Devon McCormick]

This sounds like it's related to the other bug I uncovered with the large
vector of large vectors.

On 11/17/06, Roger Hui <rhui000 at shaw.ca> wrote:
>
> The machine integer overflow problem is responsible
> for "nearly all binary searches .. are broken",
> including the one in "Programming Pearls" by
> Jon Bently:
>
>
> http://googleresearch.blogspot.com/2006/06/extra-extra-read-all-about-it-nearly.html
>
> When you look at x+y and you know that x and y are
> non-negative, it is very difficult to be alert to
> the fact that x+y can be negative!
>
>
>
> ----- Original Message -----
> From: Roger Hui <rhui000 at shaw.ca>
> Date: Friday, November 17, 2006 8:03 am
> Subject: Re: [Jprogramming] Oddities with /:
>
> > I have found and fixed the bug for the next release.
> > Thanks for finding and reporting this error.
> >
> > The error is in a calculation that involves the
> > vector length and the maximum value, to decide which
> > sort algorithm to use.  The example you found has
> > the right combination to cause machine integer
> > overflow.
> >
> >
> >
> > ----- Original Message -----
> > From: Henry Rich <HenryHRich at nc.rr.com>
> > Date: Friday, November 17, 2006 2:10 am
> > Subject: RE: [Jprogramming] Oddities with /:
> >
> > > I get similar behavior.  I had to change the vector length
> > > a little bit to get it to fail:
> > >
> > >   $ /:~vec=.?998005$1993426-~2^31
> > > 998005
> > >   $ /:~vec=.?1098005$1993426-~2^31
> > > |limit error
> > > |   $    /:~vec=.?1098005$1993426-~2^31
> > >
> > > The error seems to have something to do with the data:
> > >   $ /:~vec=.?1098005$1993426-~2^30
> > > 1098005
> > >
> > > or even
> > >
> > >   $ /:~vec=.?2098005$1993426-~2^30
> > > 2098005
> > >
> > > Henry Rich
> > >
> > >
> > > > -----Original Message-----
> > > > From: programming-bounces at jsoftware.com
> > > > [programming-bounces at jsoftware.com] On Behalf Of Roger Hui
> > > > Sent: Friday, November 17, 2006 1:56 AM
> > > > To: Programming forum
> > > > Subject: Re: [Jprogramming] Oddities with /:
> > > >
> > > > I can not reproduce the error in J601b.  Did you
> > > > generate your examples in a brand new session?
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: Devon McCormick <devonmcc at gmail.com>
> > > > Date: Thursday, November 16, 2006 6:49 pm
> > > > Subject: [Jprogramming] Oddities with /:
> > > >
> > > > > The numbers below are right on the edge of failure.
> > > > >
> > > > >   $ /:~vec=.?998005$1993426-~2^31  NB. This fails;
> > > > > |limit error
> > > > > |   $    /:~vec=.?998005$1993426-~2^31
> > > > >
> > > > >   $ /:~vec=.?998005$1993427-~2^31  NB. but this (1 less) is OK;
> > > > > 998005
> > > > >
> > > > >   $ /:~vec=.?998006$1993427-~2^31  NB. but this (1 more
> > > element)
> > > > > fails.|limit error
> > > > > |   $    /:~vec=.?998006$1993427-~2^31
> > > > >
> > > > >   $vec{~/:vec                      NB. However, this is
> > > > > equivalent to the
> > > > > above.
> > > > > 998006
> > > > >
> > > > >   (9!:12 '');9!:14 ''
> > > > > +-+---------------------+
> > > > > |6|j601/2006-09-04/09:20|
> > > > > +-+---------------------+
>
>
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>



-- 
Devon McCormick
^me^ at acm.
org is my
preferred e-mail