Difference generation method and apparatus

摘要

A method of generating a first difference data group from a first data group and a second data group. The first difference data group generates, in a programmable device, the second data group when applied to the first data group and the first data group when applied to the second data group. The method comprises the step of comparing the second data group with the first data group to generate a first difference data subgroup comprising first difference data items and a remainder data group, and comparing the remainder data group with the second data group to generate a second difference data subgroup comprising second difference data items. At least some of the second difference data items are compared with at least some of the first difference data items to generate a third difference data subgroup comprising third difference data items. At least some of the third difference data items comprise a combination of a first difference data item and a second difference data item and the first and second difference data items comprised in third difference data items are removed from the first and second difference data subgroups respectively to form reduced first and second difference data subgroups, the reduced first difference data subgroup and the third difference data subgroup together defining a first source-to-target difference data group and the reduced second difference group defining a first target-to-source difference data group. The first source-to-target difference data group and the first target-to-source difference data group are output to define the first difference data group.