[Solved]: Minimal basis for set of binary vectors using XOR

Problem Detail: 

I would be surprised if this isn't a well-studied problem, but I'm not sure what else to search for at this point: you're given a set of binary $n$-vectors $S \subset \{0,1\}^n$. The problem is to find another set of binary $n$-vectors $B \subset \{0,1\}^n$, with minimal size $|B|$, such that every vector in $S$ can be expressed by the XOR results of some subset of $B$ (so $B$ is essentially a basis for $S$ using XOR instead of addition and allowing only binary coefficients in the linear combination).

In a way, this is a form of PCA for binary vectors. While searching for literature on this problem, I came across the Discrete Basis Problem also discussed in this PhD thesis, which seems closely related. Instead of XOR it uses OR, and here $|B|$ is an additional input (and the task is it to minimise the error in representing $S$ with vectors from $B$). This problem is NP-hard. Does the same apply to the problem I've presented above, or is there an efficient solution? Any pointers to existing literature would be much appreciated.

Asked By : Martin Ender

Answered By : Yuval Filmus

If you treat your vectors as over the field $GF(2)$ rather than over the set $\{0,1\}$, then what you ask is to find a basis for the span of a set of vectors. This is a well-studied problem in linear algebra, which you probably know the solution for. (One option is Gaussian elimination.)

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Question Source : http://cs.stackexchange.com/questions/53331