A sorting algorithm proposed by Donald Shell in 1959 and published as shellsort. It is a variant of straight insertion sort that allows records to take long leaps rather than move one position at a time. It does this by sorting each group G⁽ⁱ⁾_j of records a distance h_i apart within the file. (The G⁽ⁱ⁾_j are disjoint and together contain all the information in the file.) This is repeated for a decreasing sequence of values h_i, and consequently increasing number of groups G⁽ⁱ⁾_j, finally ending with h_i = 1.