2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)
DOI: 10.1109/icassp.2014.6854987
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The computational complexity of a problem arising in the context of sparse optimization is considered, namely, the projection onto the set of $k$-cosparse vectors w.r.t. some given matrix $\Omeg$. It is shown that this projection problem is (strongly) \NP-hard, even in the special cases in which the matrix $\Omeg$ contains only ternary or bipolar coefficients. Interestingly, this is in contrast to the projection onto the set of $k$-sparse vectors, which is trivially solved by keeping only the $k$ largest coefficients. ; Comment: to appear in ICASSP 2014