(cholesky [[25 15 -5] [15 18 0] [-5 0 11]])
;=> [[ 5.0 0.0 0.0]
;    [ 3.0 3.0 0.0]
;    [-1.0 1.0 3.0]]

(cholesky [[18 22 54 42] [22 70 86 62] [54 86 174 134] [42 62 134 106]])
;=> [[ 4.242640687119285 0.0                0.0                0.0               ]
;    [ 5.185449728701349 6.565905201197403  0.0                0.0               ]
;    [12.727922061357857 3.0460384954008553 1.6497422479090704 0.0               ]
;    [ 9.899494936611667 1.624553864213788  1.8497110052313648 1.3926212476456026]]