[Sasview-users] [Sasview-help] bug report for version WIN 4.1.2

Fri Sep 8 10:48:05 EDT 2017

Dear Paul,

Sorry about the delay answering your question about "soft constrains".
I am thinking in two different but related lines. The whole idea came from
the use of the program IFFEFIT developed by Scott Calvin and coworkers used
to analyze EXAFS data.

The first line is related to the a-priori knowledge about the value of a
given parameter (just for example, R0). Some times we know that our
parameter should be around a given value, say R0. In order to avoid running
the fit with a fix value (that could be wrong because of lack of
information), it could be possible introducing a pennalty at the level of
the CHI2 parameter adding something like A*abs(R-R0) to the calculation of
CHI2, being A the magnitud of the pennalty. The minimization algorithm
should force R to be nearby R0 (in order to reduce CHI2) but allowing some
freedom of the other parameters to avoid a crash in the fit. In his book
XAFS for Everyone Scott Calvin cites the paper from Ellis and Freeman,
1995, DOI:10.1107/S0909049595006789 as the relevant reference.

A second interesting line, also related to a-priori knowledge of the
system, is to introduce complex relationships between parameters (let say
R1=Tan(4*P1)/P2) in order to fit not the parameter R but P1 and P2. Here P1
and P2 may be or may be not parameters already present in the model (for
example, you assume that R=a*T+b, being T the temperature of a given
experiment and a and b new empirical parameters). Some times it is easier
to relate or to constrain some parameters other than those defined in the
fitting functions.

Of course I understand that any development is a huge ammount of work but
as a user of SASVIEW I feel me obliged to try to help improving and already
very useful tool.

Yours.

Marcelo

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2017-09-02 22:50 GMT-03:00 Paul Butler <butlerpd at ...4...>:

> Glad that your first issue was solved and sorry about not getting back to
> your question from the user list.  Actually for particular feature requests
> the help list I think would be the best. also you can try emailing the
> developers list at developers at ...642...
>
> There is currently a long list of tasks from major bug fixes, to major
> revisions and including feature requests which can be viewed at
> trac.sasview.org under tickets.  A direct link to one common way to look
> at those would be http://trac.sasview.org/report/3
>
> Please feel free to suggest things that you think would be the highest
> impact for your work
>
> Regarding "soft constraints" could you elaborate what you mean?  Currently
> fairly complex equality constraints are supported though there are
> questions about how well those work when polydispersity is used.
> Inequality constraints are not supported though there is interest in seeing
> that.  Doing inequality constraints correctly is much harder which is the
> current bottleneck.
>
> CHeers
>
> Paul
>
> On Sat, Sep 2, 2017 at 1:06 PM, Marcelo Ceolin <mrceolin at ...6...> wrote:
>
>> Dear Paul.
>> Thank you very much for your care and answer.
>> It is true the difference between 4.x and 3.x about the default fitting
>> status of the parameters. In fact it is clear from the tutorial, that only
>> ready to fit parameters can be constrained.
>> For me is enough...I should only pay more attention !!!!.
>> I also sent to the user forum a comment/question about the way to suggest
>> the developers the incorporation of other features to the program.
>> In fact, the point is the possibility to introduce soft boundaries and
>> soft constrains for the parameters and more complex constrains and
>> relationships between them.
>> If you think there is a possibility to discuss the point, I will be glad
>> to give more details.
>> Thank you in advance.
>> Marcelo
>>
>> El 2 sept. 2017 1:53 PM, "Paul Butler" <butlerpd at ...4...> escribió:
>>
>>> Hi Marcelo,
>>>
>>> Sorry for the delayed response and thank you for your feedback.
>>> Addressing your two issues
>>>
>>> 1) After investigating this is not so much a bug it turns out as failure
>>> to make usage clear so thank you for bringing to our attention.  Basically
>>> the drop-down will only show parameters of the model that were selected to
>>> fit (i.e. checked in the appropriate fitting panel).  I have tested 4.1.2
>>> on windows 10 and it does seem to work properly.  However the default when
>>> loading a model is for all parameters to be unchecked so unless you
>>> deliberately check at least one parameter (in model 1 in your case) you
>>> will see nothing in the drop-down (of M1 in your case).  If you go back and
>>> check at least one parameter for fitting (probably FitPage 1 in your case?)
>>> you should then see that parameter in the dropdown.
>>>
>>> I'm thinking a statement in the fit constraints section indicating this
>>> to be the case would be appropriate?
>>>
>>> 2) This is a "known behavior" that some (many?) of us had forgotten so
>>> thank you for reminding us.  I will make sure it is made a high priority
>>> ticket.  However, this is only true for the LM optimizer. if you chose any
>>> of the other four optimizers for the fitting, those limits should be
>>> respected.  Please let us know if that is not the case.
>>>
>>> Thanks again for the feedback and hope this helps a little
>>>
>>> Cheers
>>>
>>> Paul
>>>
>>> On Thu, Aug 31, 2017 at 1:48 PM, Marcelo Ceolin <mrceolin at ...6...>
>>> wrote:
>>>
>>>> Dear Developers of SASVIEW
>>>>
>>>> I would like to report two bugs I found using the WINDOWS 4.1.2 release
>>>> of SASVIEW
>>>> 1) during the setup of SIMULTANEOUS fit and after selecting files to be
>>>> fitted and activated the ADD CONSTRINS mode, there is no PARAMETER to
>>>> select in the pull-down menu right from the parameter (please, find
>>>> attached a screen capture)
>>>>
>>>> [image: Imágenes integradas 1]
>>>>
>>>> 2) during a normal SINGLE FILE fit using the GUINIER POROD model (I
>>>> guess it has nothing to do with the model), the fiting procedure do not
>>>> take care of the limits imposed to the parameters.
>>>>
>>>> Thank you very much for your support.
>>>>
>>>> Sincerely yours.
>>>>
>>>> MARCELO CEOLIN
>>>>
>>>> --
>>>> ***********************************************************************
>>>> Prof. Dr. Marcelo Ceolin
>>>> Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas
>>>> UNLP-CONICET
>>>> Diagonal 113 y 64
>>>> Casilla de Correo 16 (sucursal 4)
>>>> (B1906ZAA) La Plata
>>>> Argentina
>>>>
>>>> Tel: +54-221-4257291 <+54%20221%20425-7291> or 4257430 (int:173 or 162)
>>>> Fax: +54-221-4254642 <+54%20221%20425-4642>
>>>> e-mail: mceolin at ...639... (work) or mrceolin at ...6...
>>>>  (private)
>>>> WEB: softmatter.quimica.unlp.edu.ar
>>>> <https://softmatter.quimica.unlp.edu.ar/?page_id=5823> (main) or
>>>> www.inifta.unlp.edu.ar
>>>> <http://www.inifta.unlp.edu.ar/quimica_de_la_materia_blanda>
>>>> ORCID ID: ORCID ID 0000-0002-2385-7803
>>>> <https://orcid.org/0000-0002-2385-7803>
>>>> Google Scholar: Google Scholar
>>>> <https://scholar.google.com.ar/citations?user=7LTN_j4AAAAJ&hl=es>
>>>> ***********************************************************************
>>>>
>>>>
>>>>
>>>> ------------------------------------------------------------
>>>> ------------------
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>>>> _______________________________________________
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>>>> Sasview-help at lists.sourceforge.net
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>>>>
>>>>
>>>
>

-- 
***********************************************************************
Prof. Dr. Marcelo Ceolin
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas
UNLP-CONICET
Diagonal 113 y 64
Casilla de Correo 16 (sucursal 4)
(B1906ZAA) La Plata
Argentina

Tel: +54-221-4257291 or 4257430 (int:173 or 162)
Fax: +54-221-4254642
e-mail: mceolin at ...639... (work) or mrceolin at ...6... (private)
WEB: softmatter.quimica.unlp.edu.ar
<https://softmatter.quimica.unlp.edu.ar/?page_id=5823> (main) or
www.inifta.unlp.edu.ar
<http://www.inifta.unlp.edu.ar/quimica_de_la_materia_blanda>
ORCID ID: ORCID ID 0000-0002-2385-7803
<https://orcid.org/0000-0002-2385-7803>
Google Scholar: Google Scholar
<https://scholar.google.com.ar/citations?user=7LTN_j4AAAAJ&hl=es>
***********************************************************************
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