Module: ppl/ppl Branch: master Commit: bf81124478b8102147d413f69d8c23177f4911fe URL: http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commit;h=bf81124478b81...
Author: Enea Zaffanella zaffanella@cs.unipr.it Date: Wed Jun 27 10:20:11 2012 +0200
Improved section announcing sparse/dense row representation adoption.
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NEWS | 46 ++++++++++++++++++++++++++++++++++++++-------- 1 files changed, 38 insertions(+), 8 deletions(-)
diff --git a/NEWS b/NEWS index f220beb..fac7d33 100644 --- a/NEWS +++ b/NEWS @@ -15,14 +15,44 @@ NEWS for version 1.0 (released on June 28, 2012) New and Changed Features ========================
-o Added a generic interface for sequences of coefficients enabling a - seamless switch between the dense or the sparse row representation. - The implementation of many library entities (linear expressions, - constraints, generators, congruences, and their systems) can now be - tailored to the specific usage context, sometimes leading to - significant memory space savings (e.g., for constraint systems - describing weakly relational abstractions such as boxes and - octagonal shapes). +o Significant improvements have been obtained in both time and space + resource usage by the definition of data structures and algorithms + for the case of "sparse rows", i.e., sequences of coefficients + where most of the values are zero. + +o The library fully supports two different representations for rows: + the "dense" representation is an array-like representation tailored + to sequences having most of their coefficients different from zero; + the "sparse" representation saves memory space (as well as CPU + cycles) when most of the coefficients in the sequence are zero. + +o A generic interface allows for a seamless interaction between the + dense and the sparse row representation. Most library entities + (linear expressions, constraints, generators, congruences, and + their systems) can be built using either representation, specified + as a constructor's argument. + +o As a by-product of this sparse/dense refactoring work, efficiency + improvements have been obtained even for those computations that + are still based on the dense row representation. + +o Reasonable default values for the row representation are provided + for each library entity, automatically leading to significant + memory space savings even in old client/library code, e.g., when + dealing with constraint systems describing weakly relational + abstractions such as boxes and octagonal shapes. + +o If desired, these default values can be customized to user's needs + by changing just a few lines of library code. For instance, the + constraint systems stored inside C_Polyhedron and NNC_Polyhedron + objects can be made to use the sparse representation by just + changing the following line in Polyhedron.defs.hh: + + static const Representation default_con_sys_repr = DENSE; + + to become + + static const Representation default_con_sys_repr = SPARSE;
Bugfixes