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Last modified: 28 September 2015

URL: http://cxc.harvard.edu/ciao/releasenotes/ciao_2.1.2_release.html

CIAO 2.1.2 Release Notes


Sherpa

 - Changes to Optimization Methods resulted in a factor of 2-3 speedup for 
   LEVENBERG-MARQUARDT alone, with speedups of up to an order of magnitude 
   possible, depending on the circumstances of the fit.  Here are the 
   details:

      * The RMF convolution function has been rewritten to reduce
        execution time.  (This helps reduce the time-to-convergence
        for *all* optimization methods, not just LEVENBERG-MARQUARDT.)

      *	The LEVENBERG-MARQUARDT function has been rewritten to reduce
	execution time, with unnecessary model evaluations removed.

      *	LEVENBERG-MARQUARDT has three new parameters: smplx, smplxep,
	and smplxit.  If smplx = 1, the LM fit is "refined" with a
	Simplex fit (the default value for smplx is 0).  Simplex refinement
	can be useful for complicated fitting problems where straight
	LM does not provide a quick solution.  Switchover from LM to 
 	simplex occurs when delta(stat) from one iteration to the next is
        less than lev-mar.smplxep, for lev-mar.smplxit iterations in a row.
	For example, the default is for switchover to occur when 
	delta chi**2 < 1 for 3 iterations in a row.

      *	The convergence criterion algorithm for SIMPLEX was altered so
	as to reduce the number of iterations needed for a fit.

      * A thread describing the simplex refinement of a lev-marq fit  
        is available at

 	http://cxc.harvard.edu/ciao/threads/sherpa.levmar.html

 - Changes to I/O

      *	The user can specify parameter step sizes using the DELTA parameter.
	Step sizes are used by the optimization methods to determine where
	to sample parameter space: if the value of a parameter is known well
	(such as would be the case with a line centroid energy), specifying
	a small delta may lead to a substantially faster and better fit than
	using the default value (which is 1% of the parameter value).
	
	The user may specify delta

	a) at the model parameter value prompt:
		gem1.LineE [0.5] 0.552:0.548:0.554:1.e-5
                                 init  min   max   delta
          
	b) on the command-line with other model parameter values:
		sherpa> gem1.LineE = 0.552:0.548:0.554:1.e-5
                	             init  min   max   delta

	c) directly:
		sherpa> gem1.LineE.delta = 1.e-5

      * The delta function in one-dimension can no longer be specified as
	either DELTA or DELTA1D, but only as DELTA1D.

dmextract

	- Fixed problem when region exented beyond the edge of field.
	  Currently, counts will be correctly counted; however, the 
	  area computation is still incorrect. [5479]
	- Users can now extract radial profiles from images whose
	  pixel values are not integers.  For example, users trying to
	  create radial profile from mkpsf output were getting
	  incorrect results [5490]
	- Restored support for the PHA_MIN/PHA_MAX columns which were
	  inadvertently removed from the type I PHA file
	  output. [5537]
	- Dmextract was weighting the images by the binning factor. 
	  This was not the correct calculation due to the nature of 
	  the exposure maps. Now the weighted maps are weighted by 
	  the number of pixels instead of the area.[5538]
	- When exposure maps were being used, the area would
	  incorrectly be computed (different from above).[5585]

	- Known Issue: A current limitation in dmextract fails to account 
	  for regions and x,y subspaces defined in the input file. This 
	  limitation also does not account for excluded regions in the 
	  input file.  It will be fixed in CIAO 2.2. [bug 5475]"

Last modified: 28 September 2015
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