Changeset 5151


Ignore:
Timestamp:
Jan 21, 2022 2:51:28 PM (5 months ago)
Author:
toby
Message:

improve seq. ref. constraint warning

Files:
2 edited

Legend:

Unmodified
Added
Removed
  • Tutorials/SeqRefine/SequentialTutorial.htm

    r5039 r5151  
    20562056<P></P>
    20572057<p class=MsoNormal>
    2058 For the initial fitting of datasets over a range of conditions, we
    2059 will want to start from the fitted values we have fit, but only refine
    2060 a minimal number of parameters until the scale factor, background and
    2061 lattice parameters have been optimized for each dataset and more
    2062 variables can be added back.
    20632058<P></P>
    20642059<p class=MsoNormal>There is one significant way that sequential
     
    20702065
    20712066<P></P>
    2072 <p class=MsoNormal><I>
     2067<p class=MsoNormal style='PADDING-LEFT:0.25in'><I>
     2068More details:
    20732069Note that GSAS-II shows the user unit cell parameters in the
    20742070traditional a, b, c, &#945;, &#946; & &#947; (distances in &#8491, angles in
     
    20952091</I>
    20962092
    2097 
    20982093<H3>1. Remove refinement of sensitive parameters (lattice, phase
    20992094fractions, size/&#956;strain, background peak and sample displacement)
    21002095and add refinement of the <tt>D<I>ij</i></tt> terms.</H3>
     2096
     2097<p class=MsoNormal style='PADDING-LEFT:0.25in'>
     2098For the initial fitting of datasets over a range of conditions, we
     2099will want to start from the fitted values we have fit, but until
     2100we have reasonably good values for the scale factor, background and
     2101lattice parameters, we do not want to refine any thing else.</P>
     2102
    21012103
    21022104<OL style='PADDING-LEFT:0.75in' type="A">
     
    24602462src="SequentialTutorial_files/image075.png" v:shapes="Picture_x0020_77"><![endif]></span></p>
    24612463
    2462 <P></P><LI>
     2464  <P></P><LI>
     2465  <B><I>Important:</I></B>
    24632466  Check the "<b>Copy results to next histogram</b>?" checkbox. When this
    24642467  is selected, the parameters obtained after fitting each histogram
    24652468  will be used as the starting point for the next fit, which is
    24662469  essential here since the lattice parameters change considerably. If
    2467   this were not selected, then refinement of each histogram would
    2468   start with the current parameters -- that were obtained from fitting
    2469   the first (~7 K) dataset.
    2470   The first few refinements will go well, but when reaching datasets
     2470  this were not selected, then refinement for <I>each histogram</I> would
     2471start with the current parameters for that histogram --
     2472these were obtained from fitting the first (~7 K) dataset. If we did that
     2473  the first few refinements will go well, but when reaching datasets
    24712474  where the temperature
    24722475  was sufficiently different from 7 K, the starting lattice parameters may be
    24732476  too far off and the refinements will fail. Even if that were not
    2474   true, since the temperatures increase in the series, the previous
    2475   histogram will have the closest set of lattice parameters and will
    2476   thus refine most quickly. </p>
     2477true, since the temperatures are fairly close between datasets in the
     2478series,
     2479each fit will start with a fairly close to correct set of lattice
     2480  parameters and thus fewer cycles of refinement will be needed to get
     2481  to the correct values.
     2482</p>
    24772483
    24782484<P></P><LI>Also on the Controls window, change the <B>Max cycles</B>
     
    24932499once the histograms were selected for a sequential fit in the previous
    24942500step, the menu command was relabeled from Calculate/Sequential
    2495 refine.) The refinement may take a few minutes as each of the 17
     2501refine.)</P><P></P>
     2502<p class=MsoListParagraphCxSpMiddle <p
     2503style='PADDING-LEFT:0.25in'><I>Note that a window
     2504saying "There were constraint warnings..." will be generated.
     2505This is because we have specified a constraint on the phase
     2506fractions in <A href="#I.3">step I.3</A>, but we are no longer varying
     2507them, so this constraint must be ignored.
     2508Also note the discussion on <A href="#VI.1.F">sequential fit
     2509constraint modes</A> in step VI, below.
     2510This alert is shown to provide a chance to review
     2511possible problems with constraints and not continue with the fit,
     2512when this indicates that something has been left out from the varied
     2513parameters. However, in this case, this phase fraction constraint
     2514will be fine to ignore since we do not want to refine phase fractions
     2515at this stage. This message will stop being shown when phase fractions
     2516are refined again (or if the constraint would be removed). Press
     2517"Yes" to continue with this initial sequential fit, as this
     2518warning can be ignored.
     2519<P></P></I>
     2520<p class=MsoListParagraphCxSpMiddle>
     2521The refinement may take a few minutes as each of the 17
    24962522datasets are fit in turn.</p>
    2497 
    2498 
    24992523<h3>3. Accept the sequential refinement results.</h3>
    25002524
     
    26392663
    26402664  <P></P><LI>
     2665  <A name="VI.1.F"></A>
    26412666  Select the <B>Constraints</B> data tree item and note that the
    26422667  second line of controls that appears for sequential fits.
     
    26442669
    26452670   <P></P>
    2646   <p class=MsoListParagraphCxSpMiddle>
     2671</OL>
     2672  <p class=MsoListParagraphCxSpMiddle style='PADDING-LEFT:0.25in'>
    26472673  <I>Note:
    26482674  Refinement of phase
     
    26512677  As of version 5038 of GSAS-II three modes were added for constraints
    26522678  in sequential refinements.
    2653   <UL style='PADDING-LEFT:0.75in'>
     2679  <UL style='PADDING-LEFT:1.0in'>
    26542680    <LI>In </I>"Ignore unless hist=*"<I> mode (which was
    26552681  the only mode prior to this version), any constraints with a
     
    26672693    </UL>
    26682694    </I>
    2669 </OL>
    26702695 
    26712696<h3>2. Perform the refinement.</h3>
  • trunk/GSASIIdataGUI.py

    r5139 r5151  
    56105610            else:
    56115611                l = str(len(allwarnings)) + ' histograms'
    5612             msg = 'There were changes to constraints needed in {}. See console output or visit Constraints data tree item for more details. Continue with refinement?'.format(l)
    5613             dlg = wx.MessageDialog(self,msg,caption='Constraint changes',style=wx.YES_NO)
     5612            msg = 'There were constraint warnings generated in {}. See console output or visit the Constraints data tree item for more details. Continue with refinement?'.format(l)
     5613            dlg = wx.MessageDialog(self,msg,caption='Constraint warnings',style=wx.YES_NO)
    56145614            dlg.CenterOnParent()
    56155615            result = wx.ID_NO
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