# GSoC Week 4: Vector framework done

This has been a tricky week. Not hectic, but rather tricky. Most of it was spent fixing the innumerable bugs that I encountered while polishing and ‘packaging’ the basic version of the new vector module – it’s in a PR here.

I cannot stress how helpful the pre-written unit and example tests were, in making things clearer and pointing out the many bugs in the first version of my code. In some cases, I spent quite some (read: a lot) of time fixing the issues, while in some, I just redid the code/API to work around the intricacies of the SymPy core. Its quite easy to get lost in there.

Currently, the following functionalities are supported stably by my code(with appropriate error handling wherever required)-

1. All basic vector operations-

b) Multiplication/Division by scalars

c) Dot/Cross product

2. Including coordinate variables (spatial variables) in vectorial expressions.

3. All basic use cases of the Del operator in vector/scalar expressions, including-

b) Divergence

c) Curl

d) Directional derivative

I know it seems a little low for something that’s based on code which is already a part of SymPy, but the whole point was to base it directly upon the SymPy core – for users not acquainted with the physics module. Moreover, with some rudimentary timing techniques, I found that on an average, the new module was able to do a set of most-basic vector operations (add, sub, dot, cross) approximately 3-4 times faster than sympy.physics.vector. But I guess it’s too early to judge now, since the new module has no overhead of coordinate systems.

I can say I am successful (hopefully all the tests on the PR should pass soon) in supporting all the functionality mentioned above, in a stable implementation – though I am still waiting for Jason and the SymPy people to review the PR. I hope it gets in soon.

The next step would be to start working on a new branch that would include the classes for coordinate systems and stationary points in 3D space (cartesian system). This is going to be tricky – the code for these classes in sympy.physics.vector is enough to prove that. As usual, the first step would be to write out the ‘expected-to-succeed’ unit and example tests. Hopefully, by that time, I would get sufficient feedback on the current PR too. But since the underlying vector framework is working well, I wouldn’t have to worry about bugs in that area – I can focus purely on the one-level-up code for multiple coordinate systems.

Cheers to a fun week! Hopefully I will be reporting just as much of progress next week too. Have a great week ahead :-).