1. A method of using a dynamic data structure for managing sparsely accessed data stored in memory of a digital computer, said method comprising a data processor of the digital computer executing computer instructions stored in a non-transitory computer readable storage medium to perform the steps of: (a) dynamically allocating and de-allocating pages of the memory to respective portions of the dynamic data structure so that allocated pages of the memory and de-allocated pages of the memory become distributed over the portions of the dynamic data structure, and the de-allocated pages of the memory include free pages that are mapped in the dynamic data structure and free pages that are not mapped in the dynamic data structure; (b) upon de-allocating an allocated page of the memory from one of the portions of the dynamic data structure, determining whether a probability of un-mapping the de-allocated page from said one of the portions of the dynamic data structure is the inverse of a superlinear function of the number of allocated pages in said one of the portions of the dynamic data structure; (c) based on the determination of the probability, determining whether or not to un-map the de-allocated page from said one of the portions of the dynamic data structure; and (d) in response to step (c) determining to un-map the de-allocated page from said one of the portions of the dynamic data structure, un-mapping the de-allocated page from said one of the portions of the dynamic data structure.