How to analyze an open source code without (or with not enough) documentation?

code-analysis, open-source

Solution

Since it's C++ code, you may find Source Navigator useful.

Problem

I got an open source code, about 15 mb. I want to understand the main algorithm used there. I started analyzing every part of that code, but I think it will take a lot of time. Are there any approaches to make process easier? I didn't do that before, so it is my first experience. This one, may be someone knows: https://launchpad.net/cuneiform-linux

Original source