Identify the algorithm (not code) for QGIS native tools

Question

The question

For someone with no knowledge in C++ (programming language used to write QGIS code), is there a way to identify based on which algorithms the different QGIS native tools are written?

Background

QGIS is open source, so the code can be inspected (used, modified etc.) by anyone. Still, you need quite a bit of technical knowledge to do so and I am not interested in the code (how the algorithm is implemented programatically), but in the algorithm it is based on: the step-by-step procedure that is software-independent and could be implemented using different codes in different programming languages and software packages.

My aim is to to understand better what happens when processing data, to critically assess the result of data processing.

Examples

Let's give some examples that should illustrate for what I'm looking for:

• Voronoi polygons can be created using Fortune's algorithm (see here as well)
• Shortest path in network can be done with Dijkstra's algorithm
• Generalization of a polyline can be done using Ramer–Douglas–Peucker algorithm
• A convex hull can be constructed with Graham scan

etc.

How can I check if indeed QGIS uses e.g. Fortune's algorithm to create Voronoi polygons or which other algorithm is used?

Answer 1

You will need to check the documentation and if that doesn't mention the algorithm used then inspecting the code or contacting the author of the code is the only way. In fact the only way to be really sure is to inspect the code as the code may have been updated with out matching changes being made to the documentation. You will probably have to dig down through several projects as in many cases QGis just calls GEOS which is mostly a port of JTS.

As you work through this project I would suggest that you add your findings to the documentation to save others having the same issue.