Here in France they have fucking autism and I'm supposed to do it "by hand" (no calculator other than a shitty fx-92) so I can't rely on the spectral theorem, so I'm left with the LDLT method (which gets fucked up if I need to do a permutation) and the q-reduction gauss algorithm (which also gets fucked up if there aren't enough squares)
Got any tips/rules of thumb ?
Also I'd look somewhere else but I can't find much information on the topic