15188179
Advanced Program Analyses and Verifications
Software validation and verification are critical for almost systems whose failure is unacceptable. This is a very expensive process, typically costing 50% of the total softwar e development costs. We show in this paper how program analyses can be used automatically to perform efficient and effective ver ifications, e.garray bound checking and uninitialized variable checking. These verifications are based onarray regions, the analyses that collect information about the way array elements used and de fined by programs. With useful knowledge of the program properties provided by these static analyses, the amount of additional code necess ary to instrument the application is reduced to a minimum. Run-time checks are generated only when we do not know how to prove that they are useless. Dynamic errors that may cause potentially failure are caught and their consequences can be reduced by exceptio n handling. Information provided by our analyses is helpful for the debugging process of large scale programs. All verification s are implemented in PIPS, the research compiler developed at́ Ecole des Mines de Paris. Qualitative and quantitative experimen ts have done with industrial applications up to hundreds of thousand lines of code.
9934244
Alias Verification for Fortran Code Optimization
Alias analysis for Fortran is less complicated than for programming languages with pointers but many real Fortran programs violate the standard: a formal parameter or a common variable that is aliased with another formal parameter is modified. Compilers, assuming standard-conforming programs, consider that an assignment to one variable will not change the value of any other variable, allowing optimizations involving the aliased variables. Higher performance results but anything may happen: the program may appear to run normally, or produce incorrect answers, or behave unpredictably. The results may depend on the compiler and the optimization level. To guarantee the standard conformance of programs in order to make program analyses exact and program optimizations safe, precise alias information, i.e the determination of overlaps among arrays is studied in this paper. Static analyses and code instrumentation are used to find all violations of the aliasing rules in Fortran code. Alias violation tests are inserted only at places where it cannot be proved statically that they are useless in order to reduce the number of dynamic checks at run-time. A specific memory location naming technique is used to obtain compact representation and to enhance the precision of alias analysis. Modifications on the dependence graph created by aliasing are also studied to show the impact of aliases on the correctness of some program optimizing transformations. Experimental results on SPEC95 CFP benchmark are presented and some related issues are also discussed.
7004938
Flexible and Manageable Delegation of Authority in RBAC
One of the most challenging problems in managing large networks is the complexity of security administration. Role based access control (RBAC) has become the predominant model for advanced access control. Flexibility and manageability are important requirements for any delegation system which is one of the most important access control management mechanisms in authorisation systems. This paper proposes a delegation model that satisfies these requirements.
6438691
Event-Feeded Dimension Solution
From the point of view of a data warehouse system its part of collecting and receiving information from other systems is crucial for all subsequent business intelligence applications. The incoming information can be classified generally in two types, the state-snapshot data and the state-change or event data usually called transactional data, which contains information about the change processes applied on the instances of information objects. On the way towards active data warehouses it becomes more important to provide complete data with minimal latency. We focus in this paper on dimensional data provided by any data-master application. The information transfer is done via messages containing the change-information of the dimension instances. The receiving data warehouse system is able to validate the event-messages, reconstruct the complete history of the dimension and provide a well applicable “comprehensive slowly changing dimension” (cSCD) interface for well-performing queries on the historical and current state of the dimension. A prototype implementation of “active integration” of a data warehouse is proposed.
16821874
Interactive Volume Navigation
Volume navigation is the interactive exploration of volume data sets by "flying" the viewpoint through the data, producing a volume rendered view at each frame. We present an inexpensive perspective volume navigation method designed to be run on a PC platform with accelerated 3D graphics hardware. The heart of the method is a two-phase perspective ray casting algorithm that takes advantage of the coherence inherent in adjacent frames during navigation. The algorithm generates a sequence of approximate volume-rendered views in a fraction of the time that would be required to compute them individually. The algorithm handles arbitrarily large volumes by dynamically swapping data within the current view frustum into main memory as the viewpoint moves through the volume. We also describe an interactive volume navigation application based on this algorithm. The application renders gray-scale, RGB, and labeled RGB volumes by volumetric compositing, allows trilinear interpolation of sample points, and implements progressive refinement during pauses in user input.
2066487
Maximum likelihood parameter estimation for image ringing artifact removal
At low bit rates, image compression codecs based on overlapping transforms introduce spurious oscillation known as ringing artifacts in the vicinity of major edges. The image quality can be enhanced considerably by removing the artifacts. We present a maximum likelihood approach to the ringing artifact removal problem. Our approach employs a parameter estimation method based on the k-means algorithm with the number of clusters determined by a cluster separation measure. The proposed algorithm and its simplified approximation are applied to JPEG2000 compressed images to demonstrate their effectiveness.
7825329
Zero-Latency Data Warehousing for Heterogeneous Data Sources and Continuous Data Streams
In this paper, a framework for building an overall Zero-Latency Data Warehouse system (ZLDWH) is provided. Such a ZLDWH requires tasks such as data changes detection, continuous loading and updating of new data, autonomous analysis and the execution of actions to be completed in the Data Warehouse (DWH). For this purpose, we combine (1) an existing solution for the continuous data integration and (2) the known approach of Active Data Warehousing (ADWH) by introducing protocols that enable the correct collaboration between the two. The continuous data integration is realized on the one hand by asynchronous communication between multiple information sources and the DWH through a message queuing system, and on the other hand by the continuous loading and updating. To obtain a low-latency time for this cycle, an “active rule evaluation” is provided between the data feeding stage and its loading into the DWH. This is realized by applying ECA-Techniques (EventCondition-Action) to obtain a more “active” characteristic of the DWH. A second goal of this paper is to take into consideration a special class of information source namely continuous data streams. Continuous data streams are information sources in which data arrives in high-volume, rapidly, bursty, and needs to be processed continuously. Therefore novel protocols and techniques are needed for capturing, storing and evaluate analysis decision based on new coming data from such continuous data stream sources.