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GSoC 2011 Application Vladimir Lagunov: Expression simplification
Vladimir Lagunov, 21 years, living in Russia, Novosibirsk.
Studying in magistracy of Novosibirsk state technical university, Faculty of Automatics and Computer Engineering.
How to contact me:
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email and xmpp: lagunov.vladimir at gmail.com
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xmpp: werehuman at jabber.ru
I prefer Python for my programs: i’m familiar with python much more than with other languages. Also i can write on C++, and i’m somewhat familiar with C, Java, JavaScript, PHP, Haskell. I worked with Django and Twisted.Web.
I have no large list of big projects. My first intermediate (more that 200 lines) program on Python was a xmpp-chat bot for quiz game, i wrote it 3 years ago. During last years i slightly earned by improving one site based on Django and wrote a lot of small but useful scripts for myself. Or useless but funny pieces of code like http://pastebin.com/ngRaMCVQ , that i used in internet “holywars”. Now i’m writing web-interface for my master’s thesis on twisted.web.
My experience doesn’t limited by Python only. My bachelor’s work was a DirectConnect client, written in Java and Swing (but this client doesn’t works as i wanted). Also i have some experience in C++ and Qt (concretely with QtGui and QtNetwork), and of course i can work with PyQt4/PySide.
When i was looking on GSoC projects list, my choice fell on SymPy because:
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It is a Python. I like Python.
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My masters work is very strongly associated with symbolic computations.
Alas, i am not a good mathematician, but i think i am good python programmer. I'm not good in math because earlier i didn't show interest in it, but everything have changed.
And of course i think that expression simplification doesn't need big math knowledges like ODE, but much more interesting than porting to python3, so i can cope this problem.
I have learned about SymPy just a week ago, but in few days of usage i have found some defects in simplification module. You don't need a lot of time to find that - just look to unittests of ratsimp(). Other example: current trigonomethrical simplification can reduce sin(x)**2 + cos(x)**2 to 1, but can't reduce 2*sin(x)*cos(x) to sin(2*x).
Expression simplification is an inalienable part of whole SymPy, all other components of framework are using these functional. Improving of expression simplification will affect on all parts of SymPy.
Probably when i'll start improving simplification, i'll need to work on rewriting. For example, now sympy throws attribute error when you try sinh(x).rewrite(sinh, exp) (but these transformation exists (sinh(x) = \frac 1 2 \left( e^x + e^{-x} \right) ))
TODO: This shedule is fuzzy, review it later.
- Improve ratsimp() in two weeks (probably i can do it quicker)
- Proper fraction reducing
- More tests
- Improve trigsimp() in two weeks
- Simplifying one function with one argument to other function with other argument (for example (sin(2x) = 2 sin(x) cos(x) ))
- Tests
- Extend rewrite patterns of functions in one week
- Improve simplify() in two weeks
- Checking for each expression which sub-simplify functions are giving good results
- Tests
- Improve other simplifiers if need be.
- If i'll do previous tasks earlier then expected: write function expandtrig(), that makes arguments of trigonometrical functions in specified expression as simple as possible.