OrderMat(g)
This function works as described in the GAP manual but uses the algorithm of [2] for matrices over finite fields.
gap> OrderMat( [ [ Z(17)^4, Z(17)^12, Z(17)^4, Z(17)^7 ], > [ Z(17)^10, Z(17), Z(17)^11, 0*Z(17) ], > [ Z(17)^8, Z(17)^13, Z(17)^0, Z(17)^14 ], > [ Z(17)^14, Z(17)^10, Z(17), Z(17)^10 ] ] ); 5220
ProjectiveOrderMat(g)
This function computes the least positive integer n such that g^n is scalar; it returns, as a list, n and z, where g^n is scalar in z.
gap> ProjectiveOrderMat( [ [ Z(17)^4, Z(17)^12, Z(17)^4, Z(17)^7 ], > [ Z(17)^10, Z(17), Z(17)^11, 0*Z(17) ], > [ Z(17)^8, Z(17)^13, Z(17)^0, Z(17)^14 ], > [ Z(17)^14, Z(17)^10, Z(17), Z(17)^10 ] ] ); [ 1305, Z(17)^12 ]
GAP 3.4.4