GSoC Week 6

I successfully passed my mid term evaluation this week and now the second half of my project has begun! It has been a challenging journey so far that has made me explore new algorithms (some very ingenious) and read a lot of code (much more difficult than I had imagined). This week, Mario whose code I am working on, helped in a big way by showing how and where to improve the algorithms. It is clear now that all the functions need to guarantee the order of the series they output. We were planning to keep it optional but since ring_series functions each other, an error in the order will propagate and eventually make it unpredictable.

So Far

PR 9575 is ready for merge except for a bug in sympify that converts PythonRational into float.

I had a discussion with Mario on PR 9495. He has suggested a lot of improvements while dealing with fractional exponents, especially the fact that Newton method may not be ideal in these cases. It is very interesting to try and compare different algorithms and come up with ways to optimise them for out needs. The scope for improvement is immense and we'll need to decide the order in which we'll push the optimisations.

I started writing the RingSeries class for series evaluation in PR 9614. I was supposed to update my blog yesterday, but I dozed off while working on it. According to my current approach, I am writing classes for all the functions so that they can be represented symbolically. Another issue that needs to be tackled is expansion of nested functions, things like sin(cos(sin(x)). This will need some work as there are many approaches to tackle it. Currently, I evaluate the inner functions( it they exist) recursively with prec + 1. This will work in simple cases, but not if there are cancellations, eg, sin(cos(x)) - sin(cos(x**2)).

Next Week

  • Get PR 9575 merged.

  • Improve PR 9495 and get it merged.

  • Finalise the series class hierarchy and the series evaluation function.

The next phase of my project is in Symengine and there have been a lot of improvements and changes there. I will need to play with the new stuff and perhaps also think of ways to port ring_series there.