A pile is an abstract data structure for storing data in a loosely ordered way. There are two different usages of the term

Ordered deque

The first version combines the properties of the deque and a priority queue and may be described as an ordered dequeue.

An item may be added to the head of the list if the new item is valued less than or equal to the current head or to the tail of the list if the new item is greater than or equal to the current tail. Elements may be removed from both the head and the tail.

Piles of this kind are used in the "UnShuffle sort" sorting algorithm.

Improved heap

The second version is a subject of patents and improves the heap data structure.

References