Simple 3x3 matrix inverse code (C++)

Question

What\'s the easiest way to compute a 3x3 matrix inverse?

I\'m just looking for a short code snippet that\'ll do the trick for non-singular matrices, possibly using C

Answer 1

Don't try to do this yourself if you're serious about getting edge cases right. So while they many naive/simple methods are theoretically exact, they can have nasty numerical behavior for nearly singular matrices. In particular you can get cancelation/round-off errors that cause you to get arbitrarily bad results.

A "correct" way is Gaussian elimination with row and column pivoting so that you're always dividing by the largest remaining numerical value. (This is also stable for NxN matrices.). Note that row pivoting alone doesn't catch all the bad cases.

However IMO implementing this right and fast is not worth your time - use a well tested library and there are a heap of header only ones.