A compiler method that performs parallel processing on a data set using multithreading. The method includes calculating a divisor for dividing the data set. The data set is divided into a number of subsets greater than a number of threads. The method generates a plurality of data subsets and executable code. The code performs processing operations and an instruction executed by a first thread that reaches the code. After completing processing operations related to the subsets that have been assigned to the threads, the next subsets are assigned to the threads. When assigning the next subsets, synchronous processing is performed in order to determine which one of “unprocessed”, “processed”, and “assigned to a different thread” is the state of each of the subsets.