[sage-devel] Have you considered having a Sage Journal?

2020-05-23 Thread Diego Sejas 
Hello, Sage Community!

I am not completely sure that this is the correct place to propose an idea 
like this, but I think that here it can be upvoted or downvoted, and 
commented.

I have been thinking for a long time that the Sage Community should have a 
Journal for everyone of us being able to read what is going on with Sage; 
how it is being used in research, education, etc.; what improvements have 
been made; etc., etc., etc. Perhaps an annual publication, so it is not so 
much of a burden for the editors (?).

Since the *Global Virtual SageDays 109* is approaching (yay!!!), it could 
be a good moment to discuss this idea with the community. Actually, I can 
see that somebody already asked about how people is using Sage in research, 
education, etc. (
https://ask.sagemath.org/question/51524/how-do-you-use-sagemath-in-research-education/)
 

 
That could evolve into a small journal with a few articles about the use of 
Sage, if enough people collaborate.

Please, let me know what you think.

(If this is the incorrect place to make a proposal like this, please, guide 
me to the correct resource. In any case, I am posting this same question in 
https://ask.sagemath.org/question/51529/have-you-considered-having-a-sage-journal/
.)

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[sage-devel] Have you considered having a Sage Journal?

2020-05-23 Thread Diego Sejas 


Hello, Sage Community!


I am not completely sure that this is the correct place to propose an idea 
like this, but I think that here it can be upvoted or downvoted, and 
commented.


I have been thinking for a long time that the Sage Community should have a 
Journal for everyone of us being able to read what is going on with Sage; 
how it is being used in research, education, etc.; what improvements have 
been made; etc., etc., etc. Perhaps an annual publication, so it is not so 
much of a burden for the editors (?).


Since the *Global Virtual SageDays 109* is approaching (yay!!!), it could 
be a good moment to discuss this idea with the community. Actually, I can 
see that somebody already asked 

 
about how people is using Sage in research, education, etc. That could 
evolve into a small journal with a few articles about the use of Sage, if 
enough people contribute.


Please, let me know what you think.


(If this is the incorrect place to make a proposal like this, please, guide 
me to the correct resource. In any case, I am posting this same question in 
https://ask.sagemath.org/question/51529/have-you-considered-having-a-sage-journal/.)

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[sage-devel] Please register for next week's Global Virtual SageDays 109, May 27-29

2020-05-23 Thread Matthias Koeppe 
More information: https://wiki.sagemath.org/days109 


If you are interested in participating, please register as soon as possible 
at 
https://zulip.sagemath.org/#narrow/stream/126-sd109/topic/Registration.20for.20Global.20Virtual.20SageDays.20109

Registration ahead of time is important so that the global organizers can 
order sufficient quantities of refreshment emojis 



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Re: [sage-devel] bug in matrix solve over inexact coefficients?

2020-05-23 Thread Dave Morris 
Although both behaviors may be reasonable, I don't like the fact that each 
line of the following code gives a completely different result depending on 
whether F = RR (returns a result that may be garbage, without warning) or F 
= RDF (gives an error, even though there may be a valid solution).  My own 
preference for default behavior (for F = RR, at least, which is where I 
think a naive user is likely to be working) is intermediate between these 
two, and is what I think MATLAB does: return a result but give a warning. 

sage: matrix(F, [[0]]).solve_right(vector(F, [0]))
sage: matrix(F, [[0]]).solve_right(vector(F, [1]))

Along these lines, I note that the code for 
`Matrix_generic_dense.solve_right` has

try:
X = self._solve_right_nonsingular_square(C, check_rank=True)
except NotFullRankError:
X = self._solve_right_general(C, check=check)

It seems to me that the except clause would be a good place to put a 
warning message over inexact rings. However, I know nothing about numerical 
analysis (and not much about sage), so I am certainly not giving an expert 
opinion on anything in this discussion, just the viewpoint of this sage 
user, and I apologize if it is noise.

On Saturday, May 23, 2020 at 12:30:56 PM UTC-6, Markus Wageringel wrote:
>
> Indeed, instead of ignoring the `check` keyword altogether over inexact 
> fields, it would be useful to verify the solution when that is possible, 
> such as for exact input over SR and for ball and intervall fields. I have 
> opened #29729  for this. For 
> general inexact rings though, the result cannot be verified, so it would 
> not make sense to do the check by default.
>
>
> Am Samstag, 23. Mai 2020 07:15:45 UTC+2 schrieb Dave Morris:
>>
>> From the documentation at 
>> https://www.mathworks.com/help/matlab/ref/mldivide.html, it appears to 
>> me that MATLAB gives a warning: "Warning: Matrix is close to singular or 
>> badly scaled. Results may be inaccurate."  That seems to me to be a better 
>> default behavior than what sage is doing now, but I think it would make 
>> sense to let users choose to turn off the warning (and maybe also let them 
>> upgrade it to an error).
>>
>
>  The generic implementation of `solve_right` does not provide this. I 
> would suggest to use a type that has a specialized implementation for this, 
> such as RDF, CDF, CBF. For example over RDF and CDF, a warning is issued if 
> the input is ill-conditioned and an error is raised if the matrix is 
> singular, which is a reasonable behavior:
>
> sage: matrix(RDF, [[2/3, 1], [0.4, 0.6]]).solve_right(vector(RDF, [1, 1]))
> /Applications/SageMath/src/bin/sage-ipython:1: LinAlgWarning: Ill-conditioned 
> matrix (rcond=2.77556e-17): result may not be accurate.
>   #!/usr/bin/env sage-python
> (5404319552844596.0, -3602879701896396.0)
> sage: matrix(RDF, [[0]]).solve_right(vector(RDF, [1]))
> ...
> LinAlgError: Matrix is singular.
>
>

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Re: [sage-devel] bug in matrix solve over inexact coefficients?

2020-05-23 Thread Markus Wageringel 
Indeed, instead of ignoring the `check` keyword altogether over inexact 
fields, it would be useful to verify the solution when that is possible, 
such as for exact input over SR and for ball and intervall fields. I have 
opened #29729  for this. For 
general inexact rings though, the result cannot be verified, so it would 
not make sense to do the check by default.


Am Samstag, 23. Mai 2020 07:15:45 UTC+2 schrieb Dave Morris:
>
> From the documentation at 
> https://www.mathworks.com/help/matlab/ref/mldivide.html, it appears to me 
> that MATLAB gives a warning: "Warning: Matrix is close to singular or badly 
> scaled. Results may be inaccurate."  That seems to me to be a better 
> default behavior than what sage is doing now, but I think it would make 
> sense to let users choose to turn off the warning (and maybe also let them 
> upgrade it to an error).
>

 The generic implementation of `solve_right` does not provide this. I would 
suggest to use a type that has a specialized implementation for this, such 
as RDF, CDF, CBF. For example over RDF and CDF, a warning is issued if the 
input is ill-conditioned and an error is raised if the matrix is singular, 
which is a reasonable behavior:

sage: matrix(RDF, [[2/3, 1], [0.4, 0.6]]).solve_right(vector(RDF, [1, 1]))
/Applications/SageMath/src/bin/sage-ipython:1: LinAlgWarning: Ill-conditioned 
matrix (rcond=2.77556e-17): result may not be accurate.
  #!/usr/bin/env sage-python
(5404319552844596.0, -3602879701896396.0)
sage: matrix(RDF, [[0]]).solve_right(vector(RDF, [1]))
...
LinAlgError: Matrix is singular.

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Re: [sage-devel] Physics related tutorials

2020-05-23 Thread Furkan Semih Dündar 
Dear Thierry,

I was unaware of sagemanifolds web page. It already includes many decent GR 
related tutorials. When I was a MSc student I remember using Eric's lecture 
notes on 3+1 formalism in GR.

You are right, perhaps it is best to write the tutorials first.

Thanks for the advice.

Best wishes,
Furkan.




On Saturday, May 23, 2020 at 4:15:17 PM UTC+3, Thierry 
(sage-googlesucks@xxx) wrote:
>
> Dear Furkan, 
>
> On Sat, May 23, 2020 at 05:34:36AM -0700, Furkan Semih Dündar wrote: 
> > Dear All, 
> > 
> > My name is Furkan Semih Dündar. 
> > 
> > I am a new member of the group and a physicist in Turkey. So I would 
> like 
> > to contribute physics related tutorials to the Sage web page. 
> > 
> > The topics may include classical mechanics (Lagrangian and Hamiltonian), 
> > quantum mechanics (matrix mechanics and the Schrödinger equation), 
> General 
> > relativity (if I figure out how to do tensor calculus on Sage) and so 
> on. 
>
> A good starting point seems to be https://sagemanifolds.obspm.fr/ 
>
> There are already some tutorials with explicit examples there, see the 
> "Examples" section. If you have questions, you could also ask them on 
> https://ask.sagemath.org/questions/ 
>
> > I downloaded the source code for the version 9.1 and compiled it last 
> night 
> > on Fedora 32. 
> > 
> > Are there any suggestions on how to organize the tutorials? For example 
> > should I open a separate topic on physics or include the physics related 
> > applications on math related topics? (For example classical mechanics in 
> > differential equations?) 
>
> It really depends on the content, i would suggest to first write the 
> tutorials you have in mind, and then see where they fit best 
> (sagemathfold webpage, wiki, thematic tutorials, homepage of some 
> lecture, etc). 
>
> Ciao, 
> Thierry 
>
>
> > Best wishes, 
> > Furkan. 
> > 
> > -- 
> > You received this message because you are subscribed to the Google 
> Groups "sage-devel" group. 
> > To unsubscribe from this group and stop receiving emails from it, send 
> an email to sage-...@googlegroups.com . 
> > To view this discussion on the web visit 
> https://groups.google.com/d/msgid/sage-devel/c33d2ca6-e45b-4511-8eac-8432d0b15df7%40googlegroups.com.
>  
>
>
>

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Re: [sage-devel] Physics related tutorials

2020-05-23 Thread Thierry 
Dear Furkan,

On Sat, May 23, 2020 at 05:34:36AM -0700, Furkan Semih Dündar wrote:
> Dear All,
> 
> My name is Furkan Semih Dündar.
> 
> I am a new member of the group and a physicist in Turkey. So I would like 
> to contribute physics related tutorials to the Sage web page.
> 
> The topics may include classical mechanics (Lagrangian and Hamiltonian), 
> quantum mechanics (matrix mechanics and the Schrödinger equation), General 
> relativity (if I figure out how to do tensor calculus on Sage) and so on.

A good starting point seems to be https://sagemanifolds.obspm.fr/

There are already some tutorials with explicit examples there, see the
"Examples" section. If you have questions, you could also ask them on
https://ask.sagemath.org/questions/

> I downloaded the source code for the version 9.1 and compiled it last night 
> on Fedora 32.
> 
> Are there any suggestions on how to organize the tutorials? For example 
> should I open a separate topic on physics or include the physics related 
> applications on math related topics? (For example classical mechanics in 
> differential equations?)

It really depends on the content, i would suggest to first write the
tutorials you have in mind, and then see where they fit best
(sagemathfold webpage, wiki, thematic tutorials, homepage of some
lecture, etc).

Ciao,
Thierry


> Best wishes,
> Furkan.
> 
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[sage-devel] Physics related tutorials

2020-05-23 Thread Furkan Semih Dündar 
Dear All,

My name is Furkan Semih Dündar.

I am a new member of the group and a physicist in Turkey. So I would like 
to contribute physics related tutorials to the Sage web page.

The topics may include classical mechanics (Lagrangian and Hamiltonian), 
quantum mechanics (matrix mechanics and the Schrödinger equation), General 
relativity (if I figure out how to do tensor calculus on Sage) and so on.

I downloaded the source code for the version 9.1 and compiled it last night 
on Fedora 32.

Are there any suggestions on how to organize the tutorials? For example 
should I open a separate topic on physics or include the physics related 
applications on math related topics? (For example classical mechanics in 
differential equations?)

Best wishes,
Furkan.

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