+ x_dim <- choose (1, 27)
+ y_dim <- choose (1, 27)
+ z_dim <- choose (1, 27)
+ elements <- vectorOf (x_dim * y_dim * z_dim) (arbitrary :: Gen Double)
+ let new_shape = (R.Z R.:. x_dim R.:. y_dim R.:. z_dim)
+ let fvs = R.fromListUnboxed new_shape elements