modified: doc/source/index.rst

Author: Tieqiong

Diff for: doc/source/index.rst

@@ -1,3 +1,5 @@
+.. _developers-guide-index:
+
 #######
 |title|
 #######
@@ -9,12 +11,38 @@ diffpy.srfit - SrFit - Structure refinement from diffraction data.
 | Software version |release|.
 | Last updated |today|.
 
+The diffpy.srfit package provides the framework for building a global optimizer
+on the fly from components such as function calculators (that calculate
+different data spectra), regression algorithms and structure models.  The
+software is capable of co-refinement using multiple information sources or
+models. It provides a uniform interface for various regression algorithms. The
+target function being optimized can be specified by the user according to the
+data available.
+
+Within the diffpy.srfit framework, any parameter used in describing the
+structure of a material can be passed as a refinable variable to the global
+optimizer.  Once parameters are declared as variables they can easily be turned
+"on" or "off", i.e. fixed or allowed to vary. Additionally, variables may be
+constrained to obey mathematical relationships with other parameters or
+variables used in the structural model. Restraints can be applied to
+variables, which adds a penalty to the refinement process commensurate with the
+deviation from the known value or range. The cost function can also be
+customized by the user. If the refinement contains multiple models, each model
+can have its own cost function which will be properly weighted and combined to
+obtain the total cost function. Additionally, diffpy.srfit is designed to be
+extensible, allowing the user to integrate external calculators to perform
+co-refinements with other techniques.
+
 =======
 Authors
 =======
 
-diffpy.srfit is developed by Billinge Group
-and its community contributors.
+diffpy.srfit is developed by members of the Billinge Group at
+Columbia University and at Brookhaven National Laboratory including
+Christopher L. Farrow, Pavol Juhás, Simon J.L. Billinge.
+
+The source code in *observable.py* was derived from the 1.0 version
+of the Caltech "Pyre" project.
 
 For a detailed list of contributors see
 https://github.com/diffpy/diffpy.srfit/graphs/contributors.
@@ -26,6 +54,16 @@ Installation
 See the `README <https://github.com/diffpy/diffpy.srfit#installation>`_
 file included with the distribution.
 
+===========
+Where next?
+===========
+
+.. toctree::
+   :maxdepth: 2
+
+   examples.rst
+   extending.rst
+
 =================
 Table of contents
 =================
@@ -41,4 +79,5 @@ Indices
 =======
 
 * :ref:`genindex`
+* :ref:`modindex`
 * :ref:`search`