A data processing apparatus includes a comparison unit configured to perform an element comparison process performing a comparison of a first data element at a first index in the first vector with a second data element at a second index in the second vector. A hazard vector generation unit is configured to populate a hazard vector at an index determined by the first index with a value determined by the second index. The comparison unit performs the element comparison process by iteratively comparing data elements of the first vector with each element of a subset of the second vector. It then determines the subset of the second vector as those data elements at indices in the second vector which are less than a current index of the first vector and which are greater than previously determined values of the second index for which the match condition was true.
