num::debug::verify_spd_sample

Defined in header <algebra/debug.hpp>

template <class Op, class VectorType>
void verify_spd_sample(const Op &A, idx n,
                       std::source_location loc = std::source_location::current());

Sampled test for positive definiteness \(\langle x, A x \rangle > 0\ \forall x \neq 0\).

Basis probes check the necessary condition \(A_{ii} > 0\) exactly; randomized probes then sample the quadratic form away from the axes.