From kreckel at ginac.de  Sun Jun  5 00:19:51 2011
From: kreckel at ginac.de (Richard B. Kreckel)
Date: Sun, 05 Jun 2011 00:19:51 +0200
Subject: [GiNaC-devel] indexes of clifford objects
Message-ID: <4DEAAF87.9040806@ginac.de>

Hi!

When compiling GiNaC with -DDO_GINAC_ASSERT, exam_clifford.cpp fails the 
test suite because clifford.cpp:105, assertion `is_a<varidx>(mu)' is 
violated. The function clifford_moebius_map constructs a clifford unit 
with an idx, not a varidx, if G is a matrix. The code in question was 
written by Vladimir in 2006.

 From a physicists point of view, I thought that it doesn't make sense 
to construct a clifford object with an idx instead of a varidx. But 
then, what's clifford_moebius_map doing? On the other hand, I also 
noticed that the tutorial does include examples of clifford objects with 
idx indices in section "A generic Clifford algebra". Strange.

If someone with more insight could shed a light on this I could finish 
my recent quest to make GiNaC pass its test suite even when compiled 
with -DDO_GINAC_ASSERT. That would be great.

Cheers
   -richy.
-- 
Richard B. Kreckel
<http://www.ginac.de/~kreckel/>


From kisilv at maths.leeds.ac.uk  Sun Jun  5 06:55:11 2011
From: kisilv at maths.leeds.ac.uk (Vladimir V. Kisil)
Date: Sun, 05 Jun 2011 05:55:11 +0100
Subject: [GiNaC-devel] indexes of clifford objects
In-Reply-To: <4DEAAF87.9040806@ginac.de>
References: <4DEAAF87.9040806@ginac.de>
Message-ID: <18991.1307249711@krein.leeds.ac.uk>

		Dear Richard,

>>>>> On Sun, 05 Jun 2011 00:19:51 +0200, "Richard B. Kreckel" <kreckel at ginac.de> said:
    RK> From a physicists point of view, I thought that it doesn't make
    RK> sense to construct a clifford object with an idx instead of a
    RK> varidx.

	There are several mathematical frameworks leading to Clifford
  algebras. Most elementary one is a free algebra with n generators
  factorised by an ideal of the quadratic (anticommuting)
  relations. From that perspective generators of the Clifford algebra
  are not required to be even indexed objects at all. You may call them
  simply a, b, c,... as long as you able to make manipulations like ab=-ba,
  a^2=-1, etc.

    RK> If someone with more insight could shed a light on this I could
    RK> finish my recent quest to make GiNaC pass its test suite even
    RK> when compiled with -DDO_GINAC_ASSERT. That would be great.

	However, I do not see a practical obstacle to change the GiNaC code
  to permit varidx only as indices in the clifford class.

  Best wishes,
  Vladimir
-- 
Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
--                      www: http://www.maths.leeds.ac.uk/~kisilv/



From kreckel at ginac.de  Mon Jun  6 08:24:16 2011
From: kreckel at ginac.de (Richard B. Kreckel)
Date: Mon, 06 Jun 2011 08:24:16 +0200
Subject: [GiNaC-devel] indexes of clifford objects
In-Reply-To: <18991.1307249711@krein.leeds.ac.uk>
References: <4DEAAF87.9040806@ginac.de> <18991.1307249711@krein.leeds.ac.uk>
Message-ID: <4DEC7290.6020302@ginac.de>

Dear Vladimir,

On 06/05/2011 06:55 AM, Vladimir V. Kisil wrote:
>>>>>> On Sun, 05 Jun 2011 00:19:51 +0200, "Richard B. Kreckel"<kreckel at ginac.de>  said:
>      RK>   From a physicists point of view, I thought that it doesn't make
>      RK>  sense to construct a clifford object with an idx instead of a
>      RK>  varidx.
>
> 	There are several mathematical frameworks leading to Clifford
>    algebras. Most elementary one is a free algebra with n generators
>    factorised by an ideal of the quadratic (anticommuting)
>    relations. From that perspective generators of the Clifford algebra
>    are not required to be even indexed objects at all. You may call them
>    simply a, b, c,... as long as you able to make manipulations like ab=-ba,
>    a^2=-1, etc.

Thanks for the concise reminder.

>      RK>  If someone with more insight could shed a light on this I could
>      RK>  finish my recent quest to make GiNaC pass its test suite even
>      RK>  when compiled with -DDO_GINAC_ASSERT. That would be great.
>
> 	However, I do not see a practical obstacle to change the GiNaC code
>    to permit varidx only as indices in the clifford class.

That, as opposed to making the clifford constructor accept both varidx 
and idx, would require changes to clifford_moebius_map and to the 
tutorial. Either way, can you recommend a patch?

   -richy.
-- 
Richard B. Kreckel
<http://www.ginac.de/~kreckel/>


From kisilv at maths.leeds.ac.uk  Fri Jun 10 22:17:14 2011
From: kisilv at maths.leeds.ac.uk (Vladimir V. Kisil)
Date: Fri, 10 Jun 2011 21:17:14 +0100
Subject: [GiNaC-devel] indexes of clifford objects
Message-ID: <27331.1307737034@krein.leeds.ac.uk>

               Dear Richard,

>>>>> On Mon, 06 Jun 2011 08:24:16 +0200, "Richard B. Kreckel" <
kreckel at ginac.de> said:
   RK> and to the tutorial. Either way, can you recommend a patch?

       I am attaching the patch, which admits only varidx as valid
 parameters. I Hope I did everything right.

 Best wishes,
 Vladimir
-- 
Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
--                      www: http://www.maths.leeds.ac.uk/~kisilv/
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From alexei.sheplyakov at gmail.com  Sat Jun 11 17:38:54 2011
From: alexei.sheplyakov at gmail.com (Alexei Sheplyakov)
Date: Sat, 11 Jun 2011 15:38:54 +0000
Subject: [GiNaC-devel] indexes of clifford objects
In-Reply-To: <18991.1307249711@krein.leeds.ac.uk>
References: <4DEAAF87.9040806@ginac.de>
 <18991.1307249711@krein.leeds.ac.uk>
Message-ID: <20110611153854.GA15592@vargsbox>

Hello,

On Sun, Jun 05, 2011 at 05:55:11AM +0100, Vladimir V. Kisil wrote:
>     RK> From a physicists point of view, I thought that it doesn't make
>     RK> sense to construct a clifford object with an idx instead of a
>     RK> varidx.
> 
> 	There are several mathematical frameworks leading to Clifford
>   algebras. Most elementary one is a free algebra with n generators
>   factorised by an ideal of the quadratic (anticommuting)
>   relations. From that perspective generators of the Clifford algebra
>   are not required to be even indexed objects at all. You may call them
>   simply a, b, c,... as long as you able to make manipulations like ab=-ba,
>   a^2=-1, etc.
> 
>     RK> If someone with more insight could shed a light on this I could
>     RK> finish my recent quest to make GiNaC pass its test suite even
>     RK> when compiled with -DDO_GINAC_ASSERT. That would be great.

> 
> 	However, I do not see a practical obstacle to change the GiNaC code
>   to permit varidx only as indices in the clifford class.

I don't think this artificial restrictions is a good idea. Why don't we
remove that bogus assertion instead?

Best regards,
	Alexei



From kisilv at maths.leeds.ac.uk  Sat Jun 11 19:10:17 2011
From: kisilv at maths.leeds.ac.uk (Vladimir V. Kisil)
Date: Sat, 11 Jun 2011 18:10:17 +0100
Subject: [GiNaC-devel] indexes of clifford objects
In-Reply-To: <20110611153854.GA15592@vargsbox>
References: <4DEAAF87.9040806@ginac.de> <18991.1307249711@krein.leeds.ac.uk>
	<20110611153854.GA15592@vargsbox>
Message-ID: <6794.1307812217@krein.leeds.ac.uk>

		Dear Alexei,

>>>>> On Sat, 11 Jun 2011 15:38:54 +0000, Alexei Sheplyakov <alexei.sheplyakov at gmail.com> said:
    ASh> I don't think this artificial restrictions is a good idea. Why
    ASh> don't we remove that bogus assertion instead?

	I do not qualify to participate in this discussion due to my
  limiting knowledge in software design. As a user I think that
  admitting idx make life easier, however I can survive if it will be
  restricted to varidx.

  Best wishes,
  Vladimir
-- 
Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
--                      www: http://www.maths.leeds.ac.uk/~kisilv/


From kreckel at ginac.de  Sun Jun 12 00:01:49 2011
From: kreckel at ginac.de (Richard B. Kreckel)
Date: Sun, 12 Jun 2011 00:01:49 +0200
Subject: [GiNaC-devel] indexes of clifford objects
In-Reply-To: <6794.1307812217@krein.leeds.ac.uk>
References: <4DEAAF87.9040806@ginac.de>
	<18991.1307249711@krein.leeds.ac.uk>	<20110611153854.GA15592@vargsbox>
	<6794.1307812217@krein.leeds.ac.uk>
Message-ID: <4DF3E5CD.1090703@ginac.de>

On 06/11/2011 07:10 PM, Vladimir V. Kisil wrote:
>>>>>> On Sat, 11 Jun 2011 15:38:54 +0000, Alexei Sheplyakov<alexei.sheplyakov at gmail.com>  said:
>      ASh>  I don't think this artificial restrictions is a good idea. Why
>      ASh>  don't we remove that bogus assertion instead?
>
> 	I do not qualify to participate in this discussion due to my
>    limiting knowledge in software design. As a user I think that
>    admitting idx make life easier, however I can survive if it will be
>    restricted to varidx.

Oh, in this case, I am sure this is not a question of software design!

It depends on how useful a clifford with idx is in practice. You are 
saying that allowing idx makes life easier. Well, I think this settles it.

   -richy.
-- 
Richard B. Kreckel
<http://www.ginac.de/~kreckel/>


From kisilv at maths.leeds.ac.uk  Sun Jun 12 13:57:40 2011
From: kisilv at maths.leeds.ac.uk (Vladimir V. Kisil)
Date: Sun, 12 Jun 2011 12:57:40 +0100
Subject: [GiNaC-devel] indexes of clifford objects
In-Reply-To: <4DF3E5CD.1090703@ginac.de>
References: <4DEAAF87.9040806@ginac.de> <18991.1307249711@krein.leeds.ac.uk>
	<20110611153854.GA15592@vargsbox>
	<6794.1307812217@krein.leeds.ac.uk> <4DF3E5CD.1090703@ginac.de>
Message-ID: <15698.1307879860@krein.leeds.ac.uk>

>>>>> On Sun, 12 Jun 2011 00:01:49 +0200, "Richard B. Kreckel" <kreckel at ginac.de> said:
    RK> It depends on how useful a clifford with idx is in practice. You
    RK> are saying that allowing idx makes life easier.

	Yes, in the simplistic approach to Clifford algebra there is no need
  to assign any covariance to indexes: they are simply labels to
  distinguish different generators.

    RK>  Well, I think this settles it.
	
	OK, then you can discharge the previous patch.

	Best wishes,
	Vladimir
-- 
Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
--                      www: http://www.maths.leeds.ac.uk/~kisilv/


From kreckel at ginac.de  Sun Jun 12 23:09:11 2011
From: kreckel at ginac.de (Richard B. Kreckel)
Date: Sun, 12 Jun 2011 23:09:11 +0200
Subject: [GiNaC-devel] indexes of clifford objects
In-Reply-To: <15698.1307879860@krein.leeds.ac.uk>
References: <4DEAAF87.9040806@ginac.de>
	<18991.1307249711@krein.leeds.ac.uk>	<20110611153854.GA15592@vargsbox>	<6794.1307812217@krein.leeds.ac.uk>
	<4DF3E5CD.1090703@ginac.de> <15698.1307879860@krein.leeds.ac.uk>
Message-ID: <4DF52AF7.70909@ginac.de>

Hi!

On 06/12/2011 01:57 PM, Vladimir V. Kisil wrote:
> 	Yes, in the simplistic approach to Clifford algebra there is no need
>    to assign any covariance to indexes: they are simply labels to
>    distinguish different generators.

Great! I've patched it. Thanks a lot.

Sadly, it turns out that clifford_check6 triggers yet another assertion, 
this time in clifford.cpp:1249. There, ex_to<indexed>(e.op(j)), however 
e.op(j) is actually a power object!

It seems to have been introduced by b4631c1661b1, see 
<http://www.ginac.de/pipermail/ginac-devel/2004-October/000708.html>.

Any idea?

   -richy.
-- 
Richard B. Kreckel
<http://www.ginac.de/~kreckel/>


From git at ginac.de  Sun Jun 12 23:11:36 2011
From: git at ginac.de (Richard B. Kreckel)
Date: Sun, 12 Jun 2011 23:11:36 +0200 (CEST)
Subject: [GiNaC-devel] [SCM] GiNaC -- a C++ library for symbolic
	computations branch, master, updated. release_1-4-0-356-g77c2acd
Message-ID: <20110612211136.C2FCDF00519@cebix.net>

This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GiNaC -- a C++ library for symbolic computations".

The branch, master has been updated
       via  77c2acd59e345fe7697304a865a8f41d43494129 (commit)
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- Log -----------------------------------------------------------------
commit 77c2acd59e345fe7697304a865a8f41d43494129
Author: Richard Kreckel <kreckel at ginac.de>
Date:   Sun Jun 12 23:10:07 2011 +0200

    Relax assertion in clifford ctor.
    
    Class clifford can be constructed with an idx object, now, not just
    with a varidx.

-----------------------------------------------------------------------

Summary of changes:
 ginac/clifford.cpp |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)


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From kisilv at maths.leeds.ac.uk  Mon Jun 20 23:09:51 2011
From: kisilv at maths.leeds.ac.uk (Vladimir V. Kisil)
Date: Mon, 20 Jun 2011 22:09:51 +0100
Subject: [GiNaC-devel] indexes of clifford objects
In-Reply-To: <4DF5E2CA.5050105@ginac.de>
References: <4DEAAF87.9040806@ginac.de> <18991.1307249711@krein.leeds.ac.uk>
	<20110611153854.GA15592@vargsbox>
	<6794.1307812217@krein.leeds.ac.uk> <4DF3E5CD.1090703@ginac.de>
	<15698.1307879860@krein.leeds.ac.uk> <4DF52AF7.70909@ginac.de>
	<18865.1307916450@krein.leeds.ac.uk> <4DF5E2CA.5050105@ginac.de>
Message-ID: <11426.1308604191@krein.leeds.ac.uk>

		Dear Richard,
>>>>> On Sun, 12 Jun 2011 12:13:30 +0200, "Richard B. Kreckel" <kreckel at ginac.de> said:

    RK> Sadly, it turns out that clifford_check6 triggers yet another
    RK>  assertion, this time in clifford.cpp:1249.

	I am attaching the patch. In two places a conversion to indexed
  shall be preceded by a corresponding check.

  Best wishes, 
  Vladimir
-- 
Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
--                      www: http://www.maths.leeds.ac.uk/~kisilv/
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From git at ginac.de  Tue Jun 21 21:43:30 2011
From: git at ginac.de (Jens Vollinga)
Date: Tue, 21 Jun 2011 21:43:30 +0200 (CEST)
Subject: [GiNaC-devel] [SCM] GiNaC -- a C++ library for symbolic
	computations branch, master, updated. release_1-4-0-357-g7a7b485
Message-ID: <20110621194330.59777F0053B@cebix.net>

This is an automated email from the git hooks/post-receive script. It was
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The branch, master has been updated
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      from  77c2acd59e345fe7697304a865a8f41d43494129 (commit)

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- Log -----------------------------------------------------------------
commit 7a7b485ed57429bb21e7591f4a1b0454dd1f4aae
Author: Jens Vollinga <jens.vollinga at googlemail.com>
Date:   Tue Jun 21 21:36:16 2011 +0200

    Made yyerror() string argument constant to avoid an compile error with
    gcc 4.6.

-----------------------------------------------------------------------

Summary of changes:
 ginsh/ginsh.h         |    2 +-
 ginsh/ginsh_parser.yy |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)


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From git at ginac.de  Thu Jun 23 16:28:12 2011
From: git at ginac.de (Richard B. Kreckel)
Date: Thu, 23 Jun 2011 16:28:12 +0200 (CEST)
Subject: [GiNaC-devel] [SCM] GiNaC -- a C++ library for symbolic
	computations branch, master, updated. release_1-4-0-358-g29b8244
Message-ID: <20110623142813.05331F004B7@cebix.net>

This is an automated email from the git hooks/post-receive script. It was
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The branch, master has been updated
       via  29b8244d6141ecb6f8d90480ade69af407270441 (commit)
      from  7a7b485ed57429bb21e7591f4a1b0454dd1f4aae (commit)

Those revisions listed above that are new to this repository have
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- Log -----------------------------------------------------------------
commit 29b8244d6141ecb6f8d90480ade69af407270441
Author: Vladimir V. Kisil <kisilv at maths.leeds.ac.uk>
Date:   Thu Jun 23 16:20:59 2011 +0200

    Be more careful before converting to indexed.
    
    This patch makes GiNaC pass it's test suite when compiled with
    -DDO_GINAC_ASSERT.

-----------------------------------------------------------------------

Summary of changes:
 check/exam_clifford.cpp |    3 ++-
 ginac/clifford.cpp      |   12 +++++++-----
 2 files changed, 9 insertions(+), 6 deletions(-)


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From jlhsage at gmail.com  Sun Jun 26 04:52:38 2011
From: jlhsage at gmail.com (J Sage)
Date: Sat, 25 Jun 2011 19:52:38 -0700
Subject: [GiNaC-devel] series() errors with divide by zero
Message-ID: <BANLkTinP6jN_cuWNhBgPz7s9MTMvCnztPg@mail.gmail.com>

Hi,

There is an error in ginac when taking a series of a function at
a singular point, for instance in ginsh,

> series(sqrt(x),x,3);
power::eval(): division by zero

from ginac-1.6 file power.cpp line 408.

I instrumented power.cpp with some printf functions and found
the offending dispatch to be in line 665:

         coeff = deriv.subs(r, subs_options::no_pattern);

while evaluating the third term in the expansion, presumably with
a 1/x factor.  I'm new to ginac so its taking me a while to learn the
code -- next step is to try and get it running in gdb -- so I'd appreciate
any input from the list about how ginac is handling and/or is
supposed to handle this kind of error.  Other software, like maxima,
handles the problem fine:

(%o6)                      maxima(sqrt(x), x, 0, 3)
(%i7) taylor(sqrt(x),x,0,3);

Thanks in advance,

John

*
*
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From kreckel at ginac.de  Sun Jun 26 11:33:42 2011
From: kreckel at ginac.de (Richard B. Kreckel)
Date: Sun, 26 Jun 2011 11:33:42 +0200
Subject: [GiNaC-devel] series() errors with divide by zero
In-Reply-To: <BANLkTinP6jN_cuWNhBgPz7s9MTMvCnztPg@mail.gmail.com>
References: <BANLkTinP6jN_cuWNhBgPz7s9MTMvCnztPg@mail.gmail.com>
Message-ID: <4E06FCF6.6090105@ginac.de>

Hi!

On 06/26/2011 04:52 AM, J Sage wrote:
> There is an error in ginac when taking a series of a function at
> a singular point, for instance in ginsh,
>
>  > series(sqrt(x),x,3);
> power::eval(): division by zero
>
> from ginac-1.6 file power.cpp line 408.
>
> I instrumented power.cpp with some printf functions and found
> the offending dispatch to be in line 665:
>
>           coeff = deriv.subs(r, subs_options::no_pattern);
>
> while evaluating the third term in the expansion, presumably with
> a 1/x factor.  I'm new to ginac so its taking me a while to learn the
> code -- next step is to try and get it running in gdb -- so I'd appreciate
> any input from the list about how ginac is handling and/or is
> supposed to handle this kind of error.  Other software, like maxima,
> handles the problem fine:
>
> (%o6)                      maxima(sqrt(x), x, 0, 3)
> (%i7) taylor(sqrt(x),x,0,3);

GiNaC can only compute Taylor and Laurent series. Your's is a Puiseux 
series: a series not in integer powers of x but in rational powers of x.

The Puiseux expansion of sqrt(x) is, well, x^(1/2).

You may try to set x=y^q and compute the Laurent expansion in y. Setting 
q=2 in your case would give the desired result:

   series(sqrt(x),x,0,3)
     = series(sqrt(y^2),y,0,3*2)
     = y
     = x^(1/2).

Note that the member functions degree() and ldegree() currently return 
int, so this would have to be generalized somehow, when implementing 
Puiseux series directly in GiNaC.

Bye
   -richy.
-- 
Richard B. Kreckel
<http://www.ginac.de/~kreckel/>


From jlhsage at gmail.com  Mon Jun 27 07:09:46 2011
From: jlhsage at gmail.com (J Sage)
Date: Sun, 26 Jun 2011 22:09:46 -0700
Subject: [GiNaC-devel] series() errors with divide by zero
In-Reply-To: <4E06FCF6.6090105@ginac.de>
References: <BANLkTinP6jN_cuWNhBgPz7s9MTMvCnztPg@mail.gmail.com>
	<4E06FCF6.6090105@ginac.de>
Message-ID: <BANLkTins=Ebv60kwEFYdshHY7X4axxU=gQ@mail.gmail.com>

...
>  series(sqrt(x),x,0,3)
>    = series(sqrt(y^2),y,0,3*2)
>    = y
>    = x^(1/2).
>
> Note that the member functions degree() and ldegree() currently return int,
> so this would have to be generalized somehow, when implementing Puiseux
> series directly in GiNaC.
>
> Bye
>  -richy.
> --
> Richard B. Kreckel
> <http://www.ginac.de/~kreckel/>
>

Actually, ginac cannot do a series on x^n or on sqrt(x^2).  Here's the ginsh
output:

> series(x^n,x,1);
(0^n)+Order(x)
> series(x^n,x,2);
power::eval(): division by zero
> series(sqrt(x^2),x,3);
power::eval(): division by zero
>

John
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From kreckel at ginac.de  Mon Jun 27 08:27:59 2011
From: kreckel at ginac.de (Richard B. Kreckel)
Date: Mon, 27 Jun 2011 08:27:59 +0200
Subject: [GiNaC-devel] series() errors with divide by zero
In-Reply-To: <BANLkTins=Ebv60kwEFYdshHY7X4axxU=gQ@mail.gmail.com>
References: <BANLkTinP6jN_cuWNhBgPz7s9MTMvCnztPg@mail.gmail.com>	<4E06FCF6.6090105@ginac.de>
	<BANLkTins=Ebv60kwEFYdshHY7X4axxU=gQ@mail.gmail.com>
Message-ID: <4E0822EF.5020606@ginac.de>

Hi!

On 06/27/2011 07:09 AM, J Sage wrote:
>     ...
>       series(sqrt(x),x,0,3)
>         = series(sqrt(y^2),y,0,3*2)
>         = y
>         = x^(1/2).
>
>     Note that the member functions degree() and ldegree() currently
>     return int, so this would have to be generalized somehow, when
>     implementing Puiseux series directly in GiNaC.
>
>     Bye
>       -richy.
>     --
>     Richard B. Kreckel
>     <http://www.ginac.de/~kreckel/ <http://www.ginac.de/%7Ekreckel/>>
>
>
> Actually, ginac cannot do a series on x^n or on sqrt(x^2).  Here's the
> ginsh output:
>
>  > series(x^n,x,1);
> (0^n)+Order(x)
>  > series(x^n,x,2);
> power::eval(): division by zero
>  > series(sqrt(x^2),x,3);
> power::eval(): division by zero

Oh, you're so right! Actually, that's because the result of 
series(sqrt(x^2),x==0,3) is not necessarly x: it could just as well be 
-x. The presence of the branch point makes it more tricky.

Sorry for not being able to help.

Bye
   -richy.
-- 
Richard B. Kreckel
<http://www.ginac.de/~kreckel/>