195862583
Convergent scheduling
Convergent scheduling is a general framework for cluster assignment and instruction scheduling on spatial architectures. A convergent scheduler is composed of independent passes, each implementing a heuristic that addresses a particular problem or constraint. The passes share a simple, common interface that provides spatial and temporal preference for each instruction. Preferences are not absolute; instead, the interface allows a pass to express the confidence of its preferences, as well as preferences for multiple space and time slots. A pass operates by modifying these preferences. By applying a series of passes that address all the relevant constraints, the convergent scheduler can produce a schedule that satisfies all the important constraints. Because all passes are independent and need to understand only one interface to interact with each other, convergent scheduling simplifies the problem of handling multiple constraints and co-developing different heuristics. We have applied convergent scheduling to two spatial architectures: the Raw processor and a clustered VLIW machine. It is able to successfully handle traditional constraints such as parallelism, load balancing, and communication minimization, as well as constraints due to preplaced instructions, which are instructions with predetermined cluster assignment. Convergent scheduling is able to obtain an average performance improvement of 21% over the existing space-time scheduler of the Raw processor, and an improvement of 14% over state-of-the-art assignment and scheduling techniques on a clustered VLIW architecture.
7375714
Space-time scheduling of instruction-level parallelism on a raw machine
Increasing demand for both greater parallelism and faster clocks dictate that future generation architectures will need to decentralize their resources and eliminate primitives that require single cycle global communication. A Raw microprocessor distributes all of its resources, including instruction streams, register files, memory ports, and ALUs, over a pipelined two-dimensional mesh interconnect, and exposes them fully to the compiler. Because communication in Raw machines is distributed, compiling for instruction-level parallelism (ILP) requires both spatial instruction partitioning as well as traditional temporal instruction scheduling. In addition, the compiler must explicitly manage all communication through the interconnect, including the global synchronization required at branch points. This paper describes RAWCC, the compiler we have developed for compiling general-purpose sequential programs to the distributed Raw architecture. We present performance results that demonstrate that although Raw machines provide no mechanisms for global communication the Raw compiler can schedule to achieve speedups that scale with the number of available functional units.
1552510
Strength Reduction of Integer Division and Modulo Operations
Integer division, modulo, and remainder operations are expressive and useful operations. They are logical candidates to express complex data accesses such as the wrap-around behavior in queues using ring buffers. In addition, they appear frequently in address computations as a result of compiler optimizations that improve data locality, perform data distribution, or enable parallelization. Experienced application programmers, however, avoid them because they are slow. Furthermore, while advances in both hardware and software have improved the performance of many parts of a program, few are applicable to division and modulo operations. This trend makes these operations increasingly detrimental to program performance. 
 
This paper describes a suite of optimizations for eliminating division, modulo, and remainder operations from programs. These techniques are analogous to strength reduction techniques used for multiplications. In addition to some algebraic simplifications, we present a set of optimization techniques that eliminates division and modulo operations that are functions of loop induction variables and loop constants. The optimizations rely on algebra, integer programming, and loop transformations.
9352626
Implications of I/O for Gang Scheduled Workloads
The job workloads of general-purpose multiprocessors usually include both compute-bound parallel jobs, which often require gang scheduling, as well as I/O-bound jobs, which require high CPU priority for the individual gang members of the job in order to achieve interactive response times. Our results indicate that an effective interactive multiprocessor scheduler must be flexible and tailor the priority, time quantum, and extent of gang scheduling to the individual needs of each job.
50873
Exploiting two-case delivery for fast protected messaging
We propose and evaluate two complementary techniques to protect and virtualize a tightly-coupled network interface in a multicomputer. The techniques allow efficient, direct application access to network hardware in a multiprogrammed environment while gaining most of the benefits of a memory-based network interface. First, two-case delivery allows an application to receive a message directly from the network hardware in ordinary circumstances, but provides buffering transparently when required for protection. Second, virtual buffering stores messages in virtual memory on demand, providing the convenience of effectively unlimited buffer capacity while keeping actual physical memory consumption low. The evaluation is based on workloads of real and synthetic applications running on a simulator and partly on emulated hardware. The results show that the direct path is also the common path, justifying the use of software buffering. Further results show that physical buffering requirements remain low in our applications despite the use of unacknowledged messages and despite adverse scheduling conditions.
2803245
Scalar operand networks
The bypass paths and multiported register files in microprocessors serve as an implicit interconnect to communicate operand values among pipeline stages and multiple ALUs. Previous superscalar designs implemented this interconnect using centralized structures that do not scale with increasing ILP demands. In search of scalability, recent microprocessor designs in industry and academia exhibit a trend toward distributed resources such as partitioned register files, banked caches, multiple independent compute pipelines, and even multiple program counters. Some of these partitioned microprocessor designs have begun to implement bypassing and operand transport using point-to-point interconnects. We call interconnects optimized for scalar data transport, whether centralized or distributed, scalar operand networks. Although these networks share many of the challenges of multiprocessor networks such as scalability and deadlock avoidance, they have many unique requirements, including ultra-low latency (a few cycles versus tens of cycles) and ultra-fast operation-operand matching. This work discusses the unique properties of scalar operand networks (SONs), examines alternative ways of implementing them, and introduces the AsTrO taxonomy to distinguish between them. It discusses the design of two alternative networks in the context of the Raw microprocessor, and presents timing, area, and energy statistics for a real implementation. The paper also presents a 5-tuple performance model for SONs and analyzes their performance sensitivity to network properties for ILP workloads.
927509
Edge-adaptive prediction for lossless image coding
We design an edge-adaptive predictor for lossless image coding. The predictor adaptively weights a four-directional predictor together with an adaptive linear predictor based on information from neighbouring pixels. Although conceptually simple, the performance of the resulting coder is comparable to state-of-the-art image coders when a simple context-based coder is used to encode the prediction errors.
5421860
DSI: A Fully Distributed Spatial Index for Location-Based Wireless Broadcast Services
Recent announcement of the MSN Direct Service has demonstrated the feasibility and industrial interest in utilizing wireless broadcast for pervasive information services. To support location-based services in wireless data broadcast systems, a distributed spatial index (called DSI) is proposed in this paper. DSI is highly efficient because it has a linear yet fully distributed structure that facilitates multiple search paths to be naturally mixed together by sharing links. Moreover, DSI is very resilient in error-prone wireless communication environments. Search algorithms for two classical location-based queries, window queries and kNN queries, based on DSI are presented. Performance evaluation of DSI shows that DSI significantly outperforms R-tree and Hilbert Curve Index, two state-of-the-art spatial indexing techniques for wireless data broadcast
609769
Spatial Queries in Wireless Broadcast Systems
Owing to the advent of wireless networking and personal digital devices, information systems in the era of mobile computing are expected to be able to handle a tremendous amount of traffic and service requests from the users. Wireless data broadcast, thanks to its high scalability, is particularly suitable for meeting such a challenge. Indexing techniques have been developed for wireless data broadcast systems in order to conserve the scarce power resources in mobile clients. However, most of the previous studies do not take into account the impact of location information of users. In this paper, we address the issues of supporting spatial queries (including window queries and kNN queries) of location-dependent information via wireless data broadcast. A linear index structure based on the Hilbert curve and corresponding search algorithms are proposed to answer spatial queries on air. Experiments are conducted to evaluate the performance of the proposed indexing technique. Results show that the proposed index and its enhancement outperform existing algorithms significantly.
2157536
A framework for constructing features and models for intrusion detection systems
Intrusion detection (ID) is an important component of infrastructure protection mechanisms. Intrusion detection systems (IDSs) need to be accurate, adaptive, and extensible. Given these requirements and the complexities of today's network environments, we need a more systematic and automated IDS development process rather that the pure knowledge encoding and engineering approaches. This article describes a novel framework, MADAM ID, for Mining Audit Data for Automated Models for Instrusion Detection. This framework uses data mining algorithms to compute activity patterns from system audit data and extracts predictive features from the patterns. It then applies machine learning algorithms to the audit records taht are processed according to the feature definitions to generate intrusion detection rules. Results from the 1998 DARPA Intrusion Detection Evaluation showed that our ID model was one of the best performing of all the participating systems. We also briefly discuss our experience in converting the detection models produced by off-line data mining programs to real-time modules of existing IDSs.
7026830
A fully distributed spatial index for wireless data broadcast
To support location-based services in wireless data broadcast systems, a distributed spatial index (called DSI) is proposed in this paper. DSI is highly efficient because it has a linear yet fully distributed structure that naturally facilitates multiple replications of the index by sharing links in different search trees. Search algorithms for point queries, window queries, and kNN queries, based on DSI are presented. Empirical evaluation of DSI are conducted. Result shows that DSI significantly out-performs R-tree and Hilbert curve index, two state-of-the-art spatial indexing techniques for wireless data broadcast.