I need to solve a large, sparse system of linear equations from a program written in D. Ideally I'd like a library with a D-style interface, but I doubt one exists. However, D can directly access C APIs. Therefore, please suggest some libraries that solve large, sparse systems of linear equations with the following characteristics:
Exposes a C API.
Free/open source. Preferably non-copyleft, too, but this is not a hard requirement.
Well-tested and debugged. Easy to set up and use. Not written by academics just to get a paper on their method and then completely unmaintained.
The classical library for sparse problem is suite-sparse. You have packages on many systems. Matlab uses it internally.