for y in 0..4 {
let diff_p0q0 = diff!(dst, offset, offset - step);
if (diff_p0q0 != 0) && (lim1 * diff_p0q0.abs() < maxprod) {
for y in 0..4 {
let diff_p0q0 = diff!(dst, offset, offset - step);
if (diff_p0q0 != 0) && (lim1 * diff_p0q0.abs() < maxprod) {