for (int j = fromOtherColumn; j < toOtherColumn; j++) {
byte acc = 0;
ByteVectorIterator it = nonZeroRowIterator(i, fromThisColumn, toThisColumn);
while (it.hasNext()) {
it.next();
final byte prod = aTimesB(it.get(), matrix.get(it.index(), j));
acc = aPlusB(acc, prod);
}
if (acc != 0) {
result.set(i - fromThisRow, j - fromOtherColumn, acc);