fa.bianp.net

can we merge now, pleeease ?

Three months after I began to write sympy.queries, I feel it's about time to include it in sympy's trunk, so today I sent for review 4 patches that implement the complete query module. It's been a lot of fun, but it has also caused me some headaches ... specially last …

Refine module, proof of concept

The 0.6.5 release of SymPy is taking longer than expected because some bugs in the testing framework, so my query module is not merged into trunk (yet). In the meantime, I am implementing a refine module (very little code is available yet). The refine module implements a refine …

Preparing a new release

Last days I've been busy preparing the first public beta of SymPy 0.6.5. Most of the time was spent solving a bug that made documentation tests fail under python2.4, but now that this is solved, I hope that by the end of the week we could have …

Efficient DPLL algorithm

Background: DPLL is the algorithm behind SymPy's implementation of logic.inference.satisfiable After reading the original papers by Davis & Putnam [1], I managed to implement a more efficient version of the DPLL algorithm. It is 10x times faster on medium-sized problems (40 variables), and solves some wrong result bugs [2 …

Queries and performance

After some hacking on the queries module, I finally got it right without the limitations of past versions. You can check it out from my repo http://fa.bianp.net/git/sympy.git, branch master. It now relies even more on logic.inference.satisfiable(), which is just an implementation of …

Reading CNF files

The DIMACS CNF file format is used to define a Boolean expression, written in conjunctive normal form, that may be used as an example of the satisfiability problem. The new logic module (sympy.logic) can read the content of a cnf file and transform it into a boolean expression suitable …

Logic module merged

Yesterday I finally merged the logic module in sympy's official master branch, and should be released together with SymPy 0.6.5. Next thing to do: profile the code and write some docs before the release.

The boolean satisfiability problem

Most annoying problem in my implementation of the query system is that it will not solve implications if the implicates are far away from each other. For instance, if the graph of known facts is something like this

Integer ----> Rational --> Real --> Complex
  ^  ^
  |  |
  |   -------
  |         |
Prime      Even
  ^
  |
  |
MersennePrime

Then it will not know …

Initial implementation of the query system

I sent some patches to sympy-patches with an initial implementation of the query system. You can check it out by pulling from my branch: git pull http://fa.bianp.net/git/sympy.git master into your sympy repo. Some examples of what you can do (sample isympy session): In [1 …

Assumption system and automatic theorem proving. Should I be learning LISP ?

This is the third time I attempt to write the assumption system. Other attempts could be described as me following the rule: “For any complex problem, there is always a solution that is simple, clear, and wrong.” My first attempt (although better than the current assumption system) did use very …