Local search for the surgery admission planning problem

We present a model for the surgery admission planning problem, and a meta-heuristic algorithm for solving it. The problem involves assigning operating rooms and dates to a set of elective surgeries, as well as scheduling the surgeries of each day and room. Simultaneously, a schedule is created for each surgeon to avoid double bookings. The presented algorithm uses simple Relocate and Two-Exchange neighbourhoods, governed by an iterated local search framework. The problem's search space associated with these move operators is analysed for three typical fitness surfaces, representing different compromises between patient waiting time, surgeon overtime, and waiting time for children in the morning on the day of surgery. The analysis shows that for the same problem instances, the different objectives give fitness surfaces with quite different characteristics. We present computational results for a set of benchmarks that are based on the admission planning problem in a chosen Norwegian hospital

A virtual memory system for a relational associative processor

xiic xteiaLxuiiH.! ^.ssucictLive r r o c e s s o r (n.tt..r/ / is a n experimental "backend " cellular processor for imple-menting data base management systems. RAP is par-ticularly well suited to supporting Codd's relational model of data. The capacity of a RAP device imple-mented with current IC and memory technology can be estimated to contain 108 to 109 bits of associativeiy processable data. Because many data bases are larger, a virtual memory environment for RAP has been pro-posed and its performance simulated. The environ-ment incorporates conventional memories for bulk storage and a single RAP processor—both controlled by a general purpose ±ront-enu computer, m e system requires that the entire relational data base be divided into pages of size equal to one RAP cell memory. A buffer memory is added to RAP to permit the overlap of paging with processing. It has been found that user environments containing small relations or queries ex-hibiting either long processing times relative to paging requirements or some "locality " (defined as the degree to which sequences of queries reference some relations more than others) can efficiently page data between large data bases and data base machines without sig-nificant losses in performance