We present a method that reduces the problem of computing the radical
of a matrix algebra over an arbitrary field to solving systems of semi
linear equations, The complexity of the algorithm, measured in the num
ber of arithmetic operations and the total number of the coefficients
passed to an oracle for solving semilinear equations, is polynomial, A
s an application of the technique we present a simple test for isomorp
hism of semisimple modules. (C) 1997 Elsevier Science B.V.