Faster Image Transforms With Cython

Python to Cython

This is the second post on how to accelerate Python with Cython. The previous post used Cython to declare static C data types in Python, to speed up the runtime of a prime number generator. In this post we shall be modifying a more complex program, one that performs an image transform on a map. This will allow me to demonstrate some more advanced Cython techniques, such as importing C functions from the C math library, using memory views of Numpy arrays and turning off the Python global interpreter lock (GIL).

As with the previous post, we shall be making a series of Cython modifications to Python code, noting the speed improvement with each step. As we go, we’ll be using the Cython compiler’s annotation feature to see which lines are converted into C at each stage, and which lines are still using Python objects and functions. And as we tune the code to run at increasingly higher speeds, we shall be profiling it to see what’s still holding us up, and where to refocus our attention.

Although I will be using Python 3 on a Mac, the instructions I give will mostly be platform agnostic:  I will assume you have installed Cython on your system (on Windows, Linux or OS/X) and have followed and understood the installation and testing steps in my previous post. This will be essential if you are to follow the steps I outline below. As stated in the previous post, Cython is not for Python beginners.

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From Python To Cython

This longer post will show you some of the coding skills you’ll need for turning your existing Python code into the Python-C hybrid we call Cython. In doing so, we’ll be digging into some C static data types, to see how much faster Python code will run, and restructuring some Python code along the way for maximum speed.

With Cython, all the benefits of Python are still yours – easily readable code, fast development cycles, powerful high level commands, maintainability, a suite of web development frameworks, a huge standard library for data science, machine learning, imaging, databases and security, plus easy manipulation of files, documents and strings. You should still use Python for all these things – these are what Python does best. But you should also consider combining them with Cython to speed up the computationally intensive Python functions that needs to be fast. Continue reading “From Python To Cython”

Transverse Mercator With Python

Mercator mapWith global warming melting the icecaps and opening up the poles for oil exploration and tourism, I think it’s time for a new standard wall map, one that shifts those distorted map regions away from major land masses, and places the polar regions where we can see them. That way, our cruise ship and oil tanker captains can navigate more easily through the clear, blue Arctic Ocean, unimpeded by any tiresome ice-pack.

I particularly love that oil companies want to use the new Arctic Ocean sea lanes to transport their oil to market faster. Is it irony, or some form of rare, extinction-level stupidity that only comes around one every few thousand years? Hard to tell. But I digress.

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