In this summer, I will participate in Google Summer of Code (GSoC for short), a program offers student developers stipends to write code for various open source projects. My proposal for GSoC, Adding fused types to Cython files, which aims to enhance the popular machine learning library scikit-learn has been accepted and will be supervised by two mentors from scikit-learn community: Jnothman and Mechcoder.

Below, I’ll briefly describe the work I’d like to achieve during GSoC.

Proposal Abstract

The current implementation of many algorithms in scikit-learn, such as Stochastic Gradient Descent, Coordinate Descent, etc. only allow input with np.float64 and np.int64 dtypes due to the adoption of Cython fused types may result in explosion of the generated C code. However, since scikit-learn has removed Cython files from the repo and re-generate them from every build, it provides a good chance to refactor some of the “.pyx” files by introducing Cython fused types. This will allow those algorithms to support np.float32 and np.int32 dtypes data, which is currently casted into np.float64 and np.int64 respectively, and therefore reduce the waste of memory space.

You can find the detailed version of my proposal here!


Here, I’ll use an example to illustrate how Cython fused types can benefit the whole project.

mean_variance function in scikit-learn, like some algorithms I mentioned in my proposal abstract above, will explicitly cast np.float32 data into np.float64 before this pull request, which yields waste of memory. However, after we introduce Cython fused types into this function’s implementation, it can now accept np.float32 data directly.

Results of this enhancement can be visualized via memory profiling figures showed below:

  • Memory usage before using fused types

  • Memory usage after using fused types

As one can see, memory usage surrounded by the bracket drastically decrease.


I believe that scikit-learn’s memory efficiency can be hugely improved after I add fused types into existing Cython files in the project.

On the other hand, great thanks to scikit-learn community for giving me this golden opportunity to work on an open source projects I use every day.

Really Looking forward to this productive summer!