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


From: Juergen Sauermann
Subject: Re: [Bug-apl] Problem with modulo arithmetic on Gaussian integers
Date: Wed, 26 Apr 2017 17:45:52 +0200
User-agent: Mozilla/5.0 (X11; Linux i686; rv:45.0) Gecko/20100101 Thunderbird/45.2.0

Hi Peter et al,

I believe the proper way to fix this is to find the root cause of it, not to find a compiler
under which the problem does not occur. I am currently following Jays advice, but the
work on it is still ongoing.

// Jürgen



On 04/26/2017 05:28 PM, Peter Teeson wrote:
Works OK on my Early 2009 Mac Pro running macOS 10.10.5 Yosemite and APL #svn927

You have different HW but same OS & toolchain? 
So how about trying a different toolchain to see if it is the compiler etc?
Or what about trying to disassemble the coded at the point of execution?
Could it be something like missing an overflow?

Just my 0.02¢

Peter
On Apr 26, 2017, at 1:44 AM, Frederick Pitts <address@hidden> wrote:

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
  
  
  
  
   


      




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