Returns the determinant of
A, calculated efficiently from the factorization.
# File lib/matrix/lup_decomposition.rb, line 79
def det
if (@row_count != @column_count)
Matrix.Raise Matrix::ErrDimensionMismatch
end
d = @pivot_sign
@column_count.times do |j|
d *= @lu[j][j]
end
d
end