12 research outputs found
High Quality Test Generation Targeting Power Supply Noise
Delay test is an essential structural manufacturing test used to determine the maximal frequency at which a chip can run without incurring any functional failures. The central unsolved challenge is achieving high delay correlation with the functional test, which is dominated by power supply noise (PSN). Differences in PSN between functional and structural tests can lead to differences in chip operating frequencies of 30% or more. Pseudo functional test (PFT), based on a multiple-cycle clocking scheme, has better PSN correlation with functional test compared with traditional two-cycle at-speed test. However, PFT is vulnerable to under-testing when applied to delay test. This work aims to generate high quality PFT patterns, achieving high PSN correlation with functional test.
First, a simulation-based don’t-care filling algorithm, Bit-Flip, is proposed to improve the PSN for PFT. It relies on randomly flipping a group of bits in the test pattern to explore the search space and find patterns that stress the circuits with the worst-case, but close to functional PSN. Experimental results on un-compacted patterns show Bit-Flip is able to improve PSN as much as 38.7% compared with the best random fill.
Second, techniques are developed to improve the efficiency of Bit-Flip. A set of partial patterns, which sensitize transitions on critical cells, are pre-computed and later used to guide the selection of bits to flip. Combining random and deterministic flipping, we achieve similar PSN control as Bit-Flip but with much less simulation time.
Third, we address the problem of automatic test pattern generation for extracting circuit timing sensitivity to power supply noise during post-silicon validation. A layout-aware path selection algorithm selects long paths to fully span the power delivery network. The selected patterns are intelligently filled to bring the PSN to a desired level. These patterns can be used to understand timing sensitivity in post-silicon validation by repeatedly applying the path delay test while sweeping the PSN experienced by the path from low to high.
Finally, the impacts of compression on power supply noise control are studied. Illinois Scan and embedded deterministic test (EDT) patterns are generated. Then Bit-Flip is extended to incorporate the compression constraints and applied to compressible patterns. The experimental results show that EDT lowers the maximal PSN by 24.15% and Illinois Scan lowers it by 2.77% on un-compacted patterns
Parallel implementation of fractal image compression
Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.Fractal image compression exploits the piecewise self-similarity present in real images
as a form of information redundancy that can be eliminated to achieve compression. This
theory based on Partitioned Iterated Function Systems is presented. As an alternative to the
established JPEG, it provides a similar compression-ratio to fidelity trade-off. Fractal
techniques promise faster decoding and potentially higher fidelity, but the computationally
intensive compression process has prevented commercial acceptance.
This thesis presents an algorithm mapping the problem onto a parallel processor
architecture, with the goal of reducing the encoding time. The experimental work involved
implementation of this approach on the Texas Instruments TMS320C80 parallel processor
system. Results indicate that the fractal compression process is unusually well suited to
parallelism with speed gains approximately linearly related to the number of processors used.
Parallel processing issues such as coherency, management and interfacing are discussed. The
code designed incorporates pipelining and parallelism on all conceptual and practical levels
ensuring that all resources are fully utilised, achieving close to optimal efficiency.
The computational intensity was reduced by several means, including conventional
classification of image sub-blocks by content with comparisons across class boundaries
prohibited. A faster approach adopted was to perform estimate comparisons between blocks
based on pixel value variance, identifying candidates for more time-consuming, accurate
RMS inter-block comparisons. These techniques, combined with the parallelism, allow
compression of 512x512 pixel x 8 bit images in under 20 seconds, while maintaining a 30dB
PSNR. This is up to an order of magnitude faster than reported for conventional sequential
processor implementations. Fractal based compression of colour images and video sequences
is also considered.
The work confirms the potential of fractal compression techniques, and demonstrates
that a parallel implementation is appropriate for addressing the compression time problem.
The processor system used in these investigations is faster than currently available PC
platforms, but the relevance lies in the anticipation that future generations of affordable
processors will exceed its performance. The advantages of fractal image compression may
then be accessible to the average computer user, leading to commercial acceptance
Lossy Compression applied to the Worst Case Execution Time Problem
Abstract Interpretation and Symbolic Model Checking are powerful techniques in the field of testing. These techniques can verify the correctness of systems by exploring the state space that the systems occupy. As this would normally be intractable for even moderately complicated systems, both techniques employ a system of using approximations in order to reduce the size of the state space considered without compromising on the reliability of the results. When applied to Real-time Systems, and in particular Worst Case Execution Time Estimation, Abstract Interpretation and Symbolic Model Checking are primarily used to verify the temporal properties of a system. This results in a large number of applications for the techniques, from verifying the properties of components to the values given variables may take. In turn, this results in a large problem area for researchers in devising the approximations required to reduce the size of the state space whilst ensuring the analysis remains safe.
This thesis examines the use of Abstract Interpretation and Symbolic Model Checking, in particular focusing on the methods used to create approximations. To this end, this thesis introduces the ideas of Information Theory and Lossy Compression. Information Theory gives a structured framework which allows quantifying or valuing information. In other domains, Lossy Compression utilises this framework to achieve reasonably accurate approximations. However, unlike Abstract Interpretation or Symbolic Model Checking, lossy compression provides ideas on how one can find information to remove with minimal consequences. Having introduced lossy compression applications, this thesis introduces a generic approach to applying lossy compression to problems encountered in Worst Case Execution Time estimation.
To test that the generic approach works, two distinct problems in Worst Case Execution Time estimation are considered. The first of these is providing a Must/May analysis for the PLRU cache; whilst common in usage, the logical complexity of a PLRU cache renders it difficult to analyse. The second problem is that of loop bound analysis, with a particular focus on removing the need for information supplied by annotations, due to the inherent unverifiability of annotations
Combined Industry, Space and Earth Science Data Compression Workshop
The sixth annual Space and Earth Science Data Compression Workshop and the third annual Data Compression Industry Workshop were held as a single combined workshop. The workshop was held April 4, 1996 in Snowbird, Utah in conjunction with the 1996 IEEE Data Compression Conference, which was held at the same location March 31 - April 3, 1996. The Space and Earth Science Data Compression sessions seek to explore opportunities for data compression to enhance the collection, analysis, and retrieval of space and earth science data. Of particular interest is data compression research that is integrated into, or has the potential to be integrated into, a particular space or earth science data information system. Preference is given to data compression research that takes into account the scien- tist's data requirements, and the constraints imposed by the data collection, transmission, distribution and archival systems
Cruiser and PhoTable: Exploring Tabletop User Interface Software for Digital Photograph Sharing and Story Capture
Digital photography has not only changed the nature of photography and the photographic process, but also the manner in which we share photographs and tell stories about them. Some traditional methods, such as the family photo album or passing around piles of recently developed snapshots, are lost to us without requiring the digital photos to be printed. The current, purely digital, methods of sharing do not provide the same experience as printed photographs, and they do not provide effective face-to-face social interaction around photographs, as experienced during storytelling. Research has found that people are often dissatisfied with sharing photographs in digital form. The recent emergence of the tabletop interface as a viable multi-user direct-touch interactive large horizontal display has provided the hardware that has the potential to improve our collocated activities such as digital photograph sharing. However, while some software to communicate with various tabletop hardware technologies exists, software aspects of tabletop user interfaces are still at an early stage and require careful consideration in order to provide an effective, multi-user immersive interface that arbitrates the social interaction between users, without the necessary computer-human interaction interfering with the social dialogue. This thesis presents PhoTable, a social interface allowing people to effectively share, and tell stories about, recently taken, unsorted digital photographs around an interactive tabletop. In addition, the computer-arbitrated digital interaction allows PhoTable to capture the stories told, and associate them as audio metadata to the appropriate photographs. By leveraging the tabletop interface and providing a highly usable and natural interaction we can enable users to become immersed in their social interaction, telling stories about their photographs, and allow the computer interaction to occur as a side-effect of the social interaction. Correlating the computer interaction with the corresponding audio allows PhoTable to annotate an automatically created digital photo album with audible stories, which may then be archived. These stories remain useful for future sharing -- both collocated sharing and remote (e.g. via the Internet) -- and also provide a personal memento both of the event depicted in the photograph (e.g. as a reminder) and of the enjoyable photo sharing experience at the tabletop. To provide the necessary software to realise an interface such as PhoTable, this thesis explored the development of Cruiser: an efficient, extensible and reusable software framework for developing tabletop applications. Cruiser contributes a set of programming libraries and the necessary application framework to facilitate the rapid and highly flexible development of new tabletop applications. It uses a plugin architecture that encourages code reuse, stability and easy experimentation, and leverages the dedicated computer graphics hardware and multi-core processors of modern consumer-level systems to provide a responsive and immersive interactive tabletop user interface that is agnostic to the tabletop hardware and operating platform, using efficient, native cross-platform code. Cruiser's flexibility has allowed a variety of novel interactive tabletop applications to be explored by other researchers using the framework, in addition to PhoTable. To evaluate Cruiser and PhoTable, this thesis follows recommended practices for systems evaluation. The design rationale is framed within the above scenario and vision which we explore further, and the resulting design is critically analysed based on user studies, heuristic evaluation and a reflection on how it evolved over time. The effectiveness of Cruiser was evaluated in terms of its ability to realise PhoTable, use of it by others to explore many new tabletop applications, and an analysis of performance and resource usage. Usability, learnability and effectiveness of PhoTable was assessed on three levels: careful usability evaluations of elements of the interface; informal observations of usability when Cruiser was available to the public in several exhibitions and demonstrations; and a final evaluation of PhoTable in use for storytelling, where this had the side effect of creating a digital photo album, consisting of the photographs users interacted with on the table and associated audio annotations which PhoTable automatically extracted from the interaction. We conclude that our approach to design has resulted in an effective framework for creating new tabletop interfaces. The parallel goal of exploring the potential for tabletop interaction as a new way to share digital photographs was realised in PhoTable. It is able to support the envisaged goal of an effective interface for telling stories about one's photos. As a serendipitous side-effect, PhoTable was effective in the automatic capture of the stories about individual photographs for future reminiscence and sharing. This work provides foundations for future work in creating new ways to interact at a tabletop and to the ways to capture personal stories around digital photographs for sharing and long-term preservation
Parallel implementation of fractal image compression
Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.Fractal image compression exploits the piecewise self-similarity present in real images
as a form of information redundancy that can be eliminated to achieve compression. This
theory based on Partitioned Iterated Function Systems is presented. As an alternative to the
established JPEG, it provides a similar compression-ratio to fidelity trade-off. Fractal
techniques promise faster decoding and potentially higher fidelity, but the computationally
intensive compression process has prevented commercial acceptance.
This thesis presents an algorithm mapping the problem onto a parallel processor
architecture, with the goal of reducing the encoding time. The experimental work involved
implementation of this approach on the Texas Instruments TMS320C80 parallel processor
system. Results indicate that the fractal compression process is unusually well suited to
parallelism with speed gains approximately linearly related to the number of processors used.
Parallel processing issues such as coherency, management and interfacing are discussed. The
code designed incorporates pipelining and parallelism on all conceptual and practical levels
ensuring that all resources are fully utilised, achieving close to optimal efficiency.
The computational intensity was reduced by several means, including conventional
classification of image sub-blocks by content with comparisons across class boundaries
prohibited. A faster approach adopted was to perform estimate comparisons between blocks
based on pixel value variance, identifying candidates for more time-consuming, accurate
RMS inter-block comparisons. These techniques, combined with the parallelism, allow
compression of 512x512 pixel x 8 bit images in under 20 seconds, while maintaining a 30dB
PSNR. This is up to an order of magnitude faster than reported for conventional sequential
processor implementations. Fractal based compression of colour images and video sequences
is also considered.
The work confirms the potential of fractal compression techniques, and demonstrates
that a parallel implementation is appropriate for addressing the compression time problem.
The processor system used in these investigations is faster than currently available PC
platforms, but the relevance lies in the anticipation that future generations of affordable
processors will exceed its performance. The advantages of fractal image compression may
then be accessible to the average computer user, leading to commercial acceptance
Cruiser and PhoTable: Exploring Tabletop User Interface Software for Digital Photograph Sharing and Story Capture
Digital photography has not only changed the nature of photography and the photographic process, but also the manner in which we share photographs and tell stories about them. Some traditional methods, such as the family photo album or passing around piles of recently developed snapshots, are lost to us without requiring the digital photos to be printed. The current, purely digital, methods of sharing do not provide the same experience as printed photographs, and they do not provide effective face-to-face social interaction around photographs, as experienced during storytelling. Research has found that people are often dissatisfied with sharing photographs in digital form. The recent emergence of the tabletop interface as a viable multi-user direct-touch interactive large horizontal display has provided the hardware that has the potential to improve our collocated activities such as digital photograph sharing. However, while some software to communicate with various tabletop hardware technologies exists, software aspects of tabletop user interfaces are still at an early stage and require careful consideration in order to provide an effective, multi-user immersive interface that arbitrates the social interaction between users, without the necessary computer-human interaction interfering with the social dialogue. This thesis presents PhoTable, a social interface allowing people to effectively share, and tell stories about, recently taken, unsorted digital photographs around an interactive tabletop. In addition, the computer-arbitrated digital interaction allows PhoTable to capture the stories told, and associate them as audio metadata to the appropriate photographs. By leveraging the tabletop interface and providing a highly usable and natural interaction we can enable users to become immersed in their social interaction, telling stories about their photographs, and allow the computer interaction to occur as a side-effect of the social interaction. Correlating the computer interaction with the corresponding audio allows PhoTable to annotate an automatically created digital photo album with audible stories, which may then be archived. These stories remain useful for future sharing -- both collocated sharing and remote (e.g. via the Internet) -- and also provide a personal memento both of the event depicted in the photograph (e.g. as a reminder) and of the enjoyable photo sharing experience at the tabletop. To provide the necessary software to realise an interface such as PhoTable, this thesis explored the development of Cruiser: an efficient, extensible and reusable software framework for developing tabletop applications. Cruiser contributes a set of programming libraries and the necessary application framework to facilitate the rapid and highly flexible development of new tabletop applications. It uses a plugin architecture that encourages code reuse, stability and easy experimentation, and leverages the dedicated computer graphics hardware and multi-core processors of modern consumer-level systems to provide a responsive and immersive interactive tabletop user interface that is agnostic to the tabletop hardware and operating platform, using efficient, native cross-platform code. Cruiser's flexibility has allowed a variety of novel interactive tabletop applications to be explored by other researchers using the framework, in addition to PhoTable. To evaluate Cruiser and PhoTable, this thesis follows recommended practices for systems evaluation. The design rationale is framed within the above scenario and vision which we explore further, and the resulting design is critically analysed based on user studies, heuristic evaluation and a reflection on how it evolved over time. The effectiveness of Cruiser was evaluated in terms of its ability to realise PhoTable, use of it by others to explore many new tabletop applications, and an analysis of performance and resource usage. Usability, learnability and effectiveness of PhoTable was assessed on three levels: careful usability evaluations of elements of the interface; informal observations of usability when Cruiser was available to the public in several exhibitions and demonstrations; and a final evaluation of PhoTable in use for storytelling, where this had the side effect of creating a digital photo album, consisting of the photographs users interacted with on the table and associated audio annotations which PhoTable automatically extracted from the interaction. We conclude that our approach to design has resulted in an effective framework for creating new tabletop interfaces. The parallel goal of exploring the potential for tabletop interaction as a new way to share digital photographs was realised in PhoTable. It is able to support the envisaged goal of an effective interface for telling stories about one's photos. As a serendipitous side-effect, PhoTable was effective in the automatic capture of the stories about individual photographs for future reminiscence and sharing. This work provides foundations for future work in creating new ways to interact at a tabletop and to the ways to capture personal stories around digital photographs for sharing and long-term preservation
Recommended from our members
Strong, thorough, and efficient memory protection against existing and emerging DRAM errors
Memory protection is necessary to ensure the correctness of data in the presence of unavoidable faults. As such, large-scale systems typically employ Error Correcting Codes (ECC) to trade off redundant storage and bandwidth for increased reliability. Single Device Data Correction (SDDC) ECC mechanisms are required to meet the reliability demands of servers and large-scale systems by tolerating even severe faults that disable an entire memory chip. In the future, however, stronger memory protection will be required due to increasing levels of system integration, shrinking process technology, and growing transfer rates. The energy-efficiency of memory protection is also important as DRAM already consumes a significant fraction of system energy budget. This dissertation develops a novel set of ECC schemes to provide strong, safe, flexible, and thorough protection against existing and emerging types of DRAM errors. This research also reduces energy consumption of such protection while only marginally impacting performance. First, this dissertation develops Bamboo ECC, a technique with strongerthan-SDDC correction and very safe detection capabilities (≥ 99.999994% of data errors with any severity are detected). Bamboo ECC changes ECC layout based on frequent DRAM error patterns, and can correct concurrent errors from multiple devices and all but eliminates the risk of silent data corruption. Also, Bamboo ECC provides flexible configurations to enable more adaptive graceful downgrade schemes in which the system continues to operate correctly after even severe chip faults, albeit at a reduced capacity to protect against future faults. These strength, safety, and flexibility advantages translate to a significantly more reliable memory sub-system for future exascale computing. Then, this dissertation focuses on emerging error types from scaling process technology and increasing data bandwidth. As DRAM process technology scales down to below 10nm, DRAM cells are becoming more vulnerable to errors from an imperfect manufacturing process. At the same time, DRAM signal transfers are getting more susceptible to timing and electrical noises as DRAM interfaces keep increasing signal transfer rates and decreasing I/O voltage levels. With individual DRAM chips getting more vulnerable to errors, industry and academia have proposed mechanisms to tolerate these emerging types of errors; yet they are inefficient because they rely on multiple levels of redundancy in the case of cell errors and ad-hoc schemes with suboptimal protection coverage for transmission errors. Active Guardband ECC and All-Inclusive ECC make systematic use of ECC and existing mechanisms to provide thorough end-to-end protection without requiring redundancy beyond what is common today. Finally, this dissertation targets the energy efficiency of memory protection. Frugal ECC combines ECC with fine-grained compression to provide versatile and energy-efficient protection. Frugal ECC compresses main memory at cache-block granularity, using any left over space to store ECC information. Frugal ECC allows more energy-efficient memory configurations while maintaining SDDC protection. Its tailored compression scheme minimizes insufficiently compressed blocks and results in acceptable performance overhead. The strong, thorough, and efficient protection described by this dissertation may allow for more aggressive design of future computing systems with larger integration, finer process technology, higher transfer rates, and better energy efficiencyElectrical and Computer Engineerin
The Third NASA Goddard Conference on Mass Storage Systems and Technologies
This report contains copies of nearly all of the technical papers and viewgraphs presented at the Goddard Conference on Mass Storage Systems and Technologies held in October 1993. The conference served as an informational exchange forum for topics primarily relating to the ingestion and management of massive amounts of data and the attendant problems involved. Discussion topics include the necessary use of computers in the solution of today's infinitely complex problems, the need for greatly increased storage densities in both optical and magnetic recording media, currently popular storage media and magnetic media storage risk factors, data archiving standards including a talk on the current status of the IEEE Storage Systems Reference Model (RM). Additional topics addressed System performance, data storage system concepts, communications technologies, data distribution systems, data compression, and error detection and correction