<p>Actually, there is something left to do... it looks like occasionally, the initial Z matrix passed to PrimalDualSolver is not symmetric positive definite:</p>

<p><code>[FATAL] PrimalDualSolver::PrimalDualSolver(): initialZ needs to be symmetric positive definite.</code></p>

<p>(according to the errors, at least.)  This occurs sometimes in the tests:</p>

<p><a href="http://big.cc.gt.atl.ga.us/job/mlpack%20-%20nightly%20matrix%20build/">http://big.cc.gt.atl.ga.us/job/mlpack%20-%20nightly%20matrix%20build/</a></p>

<p>It looks like Armadillo 4.000 and older did not support the expression '-arma::sp_mat()'.  I'll take care of backporting that functionality shortly.</p>

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