If you are interested in reading codebases but find some of the larger projects intimidating, I suggest checking out Timothy Davis' sparse matrix library CSpars

If you are interested in reading codebases but find some of the larger projects intimidating, I suggest checking out Timothy Davis' sparse matrix library CSparse: (http://people.sc.fsu.edu/~jburkardt/c_src/csparse/csparse.html http://people.sc.fsu.edu/~jburkardt/c_src/csparse/csparse.ht...). It is is used internally for sparse matrix representations in Python, R, and Matlab. The entire library fits into 2100 lines of concise yet well documented C code. It is now mostly installed bundled with SuiteSparse, but the link above has the 2006 codebase from the original stand alone library.