Re: [Bug-apl] Problem with modulo arithmetic on Gaussian integers

[Frederick Pitts]

To all,

        I have 3 machines running 64-bit Fedora 25 Workstation with g++
(GCC) 6.3.1 20161221 (Red Hat 6.3.1-1) and either gnu-apl svn version
889 or 933.  Two of the machines are about 8 years old and one less
than a year old.

        On all three platforms, gnu-apl gives:

        3J1 | 23J1 25J25
3J1 0

        Juergen and Xtian (on svn 933) report their setups give the
right answer:

0 0

        Am I the only one seeing this problem?  BTW, I have about 1500
more examples of the modulo operator failing out of 6765201 tests with
distinct argument values.

Regards,

Fred


On Tue, 2017-04-25 at 23:01 -0400, Christian Robert wrote:
> Same result as Juergen,
> 
> Xtian.
> 
> address@hidden:/home/xtian] $ apl
> 
>                      ______ _   __ __  __    ___     ____   __
>                     / ____// | / // / / /   /   |   / __ \ / /
>                    / / __ /  |/ // / / /   / /| |  / /_/ // /
>                   / /_/ // /|  // /_/ /   / ___ | / ____// /___
>                   \____//_/ |_/ \____/   /_/  |_|/_/    /_____/
> 
>                       Welcome to GNU APL version 1.7 / 933M
> 
>                  Copyright (C) 2008-2016  Dr. Jürgen Sauermann
>                         Banner by FIGlet: www.figlet.org
> 
>                  This program comes with ABSOLUTELY NO WARRANTY;
>                            for details run: apl --gpl.
> 
>       This program is free software, and you are welcome to
> redistribute it
>           according to the GNU Public License (GPL) version 3 or
> later.
> 
> SAVED 2017-03-30 22:33:13 (GMT-4)
>        23J1 25J25 ÷ 3J1
> 7J¯2 10J5
>        3J1 | 23J1 25J25
> 0 0
> 
> 
> 
> On 2017-04-25 21:50, Frederick Pitts wrote:
> > Juergen,
> > 
> >          I did a 'make clean' followed by 'make' and 'make
> > install'.  I
> > obtained the same result that caused me to report the problem.
> > 
> >          The version of gnu-apl I'm using is svn rev 933.  From the
> > banner in your email, I see you're testing with code from your
> > personal
> > svn.  Is it possible the changes you recently made to
> > (ComplexCell.hh
> > and FloatCell.hh) are not yet in the svn from which I clone?
> > 
> > Regards,
> > 
> > Fred
> > 
> > On Tue, 2017-04-25 at 22:05 +0200, Juergen Sauermann wrote:
> > > Hi Fred,
> > >   
> > > actually it does on my machine:
> > >   
> > >                       ______ _   __ __  __    ___     ____   __
> > >                      / ____// | / // / / /   /   |   / __ \ / /
> > >                     / / __ /  |/ // / / /   / /| |  / /_/ // /
> > >                    / /_/ // /|  // /_/ /   / ___ | / ____// /___
> > >                    \____//_/ |_/ \____/   /_/  |_|/_/    /_____/
> > >                                          
> > >                    Welcome to GNU APL version 1.7 / 12784:12785M
> > >                                          
> > >                   Copyright (C) 2008-2016  Dr. Jürgen Sauermann
> > >                          Banner by FIGlet: www.figlet.org
> > >                                          
> > >                   This program comes with ABSOLUTELY NO WARRANTY;
> > >                             for details run: apl --gpl.
> > >                                          
> > >        This program is free software, and you are welcome to
> > > redistribute it
> > >            according to the GNU Public License (GPL) version 3 or
> > > later.
> > >                                          
> > >         23J1 25J25 ÷ 3J1
> > > 7J¯2 10J5
> > >   
> > >         3J1 | 23J1 25J25
> > > 0 0
> > >   
> > >   
> > > However, if I remember correctly then some of the changes that I
> > > made
> > > lately were in
> > > header files (ComplexCell.hh and FloatCell.hh). If you did
> > > ./configure without options, then
> > > your build is probably is a 'fast' one, which may not have
> > > detected
> > > header file changes.
> > >   
> > > Please try make clean at the top level and rebuild GNU APL to see
> > > if
> > > the problem persists.
> > >   
> > > Best Regards,
> > > Jürgen Sauermann
> > >   
> > >   
> > >   
> > > On 04/25/2017 09:30 PM, Frederick Pitts wrote:
> > > > Jeurgen,
> > > >   
> > > >      A greatest common divisor of 23J1 and 25J25 is 3J1.
> > > > Complex division by of 23J1 and 25J25 by 3J1 yields Gaussian
> > > > integers
> > > >   
> > > >         23J1 25J25 ÷ 3J1
> > > > 7J¯2 10J5
> > > >   
> > > > but mod 3J1 of the same numbers does not consistently yield
> > > > zeroes
> > > >   
> > > >         3J1 | 23J1 25J25
> > > > 3J1 0
> > > >   
> > > > I can provide numerous other examples of this problem if
> > > > needed.
> > > >   
> > > > Regards,
> > > >   
> > > > Fred
> > > >   
> > > >   
> > > >   
> > > >   
> > > 
> > >    
> 
>