4.9 Bibliographic Remarks
In this chapter, we studied a variety of data communication operations for the linear array, mesh, and hypercube interconnection topologies. Saad and Schultz [SS89b] discuss implementation issues for these operations on these and other architectures, such as shared-memory and a switch or bus interconnect. Most parallel computer vendors provide standard APIs for inter-process communications via message-passing. Two of the most common APIs are the message passing interface (MPI) [SOHL+96] and the parallel virtual machine (PVM) [GBD+94].
The hypercube algorithm for a certain communication operation is often the best algorithm for other less-connected architectures too, if they support cut-through routing. Due to the versatility of the hypercube architecture and the wide applicability of its algorithms, extensive work has been done on implementing various communication operations on hypercubes [BOS+91, BR90, BT97, FF86, JH89, Joh90, MdV87, RS90b, SS89a, SW87]. The properties of a hypercube network that are used in deriving the algorithms for various communication operations on it are described by Saad and Schultz [SS88].
The all-to-all personalized communication problem in particular has been analyzed for the hypercube architecture by Boppana and Raghavendra [BR90], Johnsson and Ho [JH91], Seidel [Sei89], and Take [Tak87]. E-cube routing that guarantees congestion-free communication in Algorithm 4.10 for all-to-all personalized communication is described by Nugent [Nug88].
The all-reduce and the prefix sums algorithms of Section 4.3 are described by Ranka and Sahni [RS90b]. Our discussion of the circular shift operation is adapted from Bertsekas and Tsitsiklis [BT97]. A generalized form of prefix sums, often referred to as scan, has been used by some researchers as a basic primitive in data-parallel programming. Blelloch [Ble90] defines a scan vector model, and describes how a wide variety of parallel programs can be expressed in terms of the scan primitive and its variations.
The hypercube algorithm for one-to-all broadcast using spanning binomial trees is described by Bertsekas and Tsitsiklis [BT97] and Johnsson and Ho [JH89]. In the spanning tree algorithm described in Section 4.7.1, we split the m-word message to be broadcast into log p parts of size m/log p for ease of presenting the algorithm. Johnsson and Ho [JH89] show that the optimal size of the parts is . In this case, the number of messages may be greater than log p. These smaller messages are sent from the root of the spanning binomial tree to its log p subtrees in a circular fashion. With this strategy, one-to-all broadcast on a p-node hypercube can be performed in time .
Algorithms using the all-port communication model have been described for a variety of communication operations on the hypercube architecture by Bertsekas and Tsitsiklis [BT97], Johnsson and Ho [JH89], Ho and Johnsson [HJ87], Saad and Schultz [SS89a], and Stout and Wagar [SW87]. Johnsson and Ho [JH89] show that on a p-node hypercube with all-port communication, the coefficients of tw in the expressions for the communication times of one-to-all and all-to-all broadcast and personalized communication are all smaller than those of their single-port counterparts by a factor of log p. Gupta and Kumar [GK91] show that all-port communication may not improve the scalability of an algorithm on a parallel architecture over single-port communication.
The elementary operations described in this chapter are not the only ones used in parallel applications. A variety of other useful operations for parallel computers have been described in literature, including selection [Akl89], pointer jumping [HS86, Jaj92], BPC permutations [Joh90, RS90b], fetch-and-op [GGK+83], packing [Lev87, Sch80], bit reversal [Loa92], and keyed-scan or multi-prefix [Ble90, Ran89].
Sometimes data communication does not follow any predefined pattern, but is arbitrary, depending on the application. In such cases, a simplistic approach of routing the messages along the shortest data paths between their respective sources and destinations leads to contention and imbalanced communication. Leighton, Maggs, and Rao [LMR88], Valiant [Val82], and Valiant and Brebner [VB81] discuss efficient routing methods for arbitrary permutations of messages.