AnICA: Analyzing Inconsistencies in Microarchitectural Code Analyzers

Microarchitectural code analyzers, i.e., tools that estimate the throughput of machine code basic blocks, are important utensils in the tool belt of performance engineers. Recent tools like llvm-mca, uiCA, and Ithemal use a variety of techniques and different models for their throughput predictions. When put to the test, it is common to see these state-of-the-art tools give very different results. These inconsistencies are either errors, or they point to different and rarely documented assumptions made by the tool designers. In this paper, we present AnICA, a tool taking inspiration from differential testing and abstract interpretation to systematically analyze inconsistencies among these code analyzers. Our evaluation shows that AnICA can summarize thousands of inconsistencies in a few dozen descriptions that directly lead to high-level insights into the different behavior of the tools. In several case studies, we further demonstrate how AnICA automatically finds and characterizes known and unknown bugs in llvm-mca, as well as a quirk in AMD's Zen microarchitectures.Comment: To appear in Proceedings of the ACM on Programming Languages (PACMPL), Vol. 6, No. OOPSLA

A Structured Design Methodology for High Performance VLSI Arrays

abstract: The geometric growth in the integrated circuit technology due to transistor scaling also with system-on-chip design strategy, the complexity of the integrated circuit has increased manifold. Short time to market with high reliability and performance is one of the most competitive challenges. Both custom and ASIC design methodologies have evolved over the time to cope with this but the high manual labor in custom and statistic design in ASIC are still causes of concern. This work proposes a new circuit design strategy that focuses mostly on arrayed structures like TLB, RF, Cache, IPCAM etc. that reduces the manual effort to a great extent and also makes the design regular, repetitive still achieving high performance. The method proposes making the complete design custom schematic but using the standard cells. This requires adding some custom cells to the already exhaustive library to optimize the design for performance. Once schematic is finalized, the designer places these standard cells in a spreadsheet, placing closely the cells in the critical paths. A Perl script then generates Cadence Encounter compatible placement file. The design is then routed in Encounter. Since designer is the best judge of the circuit architecture, placement by the designer will allow achieve most optimal design. Several designs like IPCAM, issue logic, TLB, RF and Cache designs were carried out and the performance were compared against the fully custom and ASIC flow. The TLB, RF and Cache were the part of the HEMES microprocessor.Dissertation/ThesisPh.D. Electrical Engineering 201

Neural Alterations Influencing Skilled Reading In Adhd: A Task-Based Fmri Study

Attention-Deficit/Hyperactivity Disorder (ADHD) is a heterogeneous, neurodevelopmental disorder which co-occurs often with Reading Disability (RD). ADHD with and without RD consistently have higher inattentive ratings compared with typically developing controls, with co-occurring ADHD and RD (ADHD/+RD) also demonstrating impaired phonological processing. Accordingly, inattention has been associated with greater phonological impairment, though neither the neural correlates of the co-occurring disorders nor the association are well understood from a functional neuroimaging perspective. The goal was to assess to what extent ADHD/+RD differ from ADHD without RD (ADHD/-RD) and typically developing controls (TDC) in functional activation of attention- and reading-related areas during various tasks. The general hypothesis was that ADHD/+RD would show more extensive alterations in attention-related areas and unique alterations in reading-related areas compared with the other two groups. The results indicated differences between ADHD/+RD and ADHD/-RD in attention processing; ADHD/-RD showed greater activation of frontoparietal areas for digit and word rhyming continuous performance fMRI tasks. Additionally, though some dysfunction was observed in decoding-related areas in ADHD/+RD relative to TDC, the results showed greater evidence of other cognitive impairments influencing decoding abilities across the ADHD/+RD and ADHD/-RD. Once the groups were re-characterized to reflect relative reading abilities in decoding and word recognition, specific cognitive and functional activation profiles surfaced for three groups: Balanced, Decoders, and Sight Readers. Two findings contribute to a better understanding of ADHD and RD. First, the functional activation differences between the ADHD subgroups suggest that RD needs to be characterized specifically in ADHD neuroimaging studies and that non-linguistic stimuli should be used to mitigate RD-related confounds in ADHD studies. Second, the role of cognitive impairments, including the level of inattention, on phonology requires clarification from a neuroimaging perspective. Lastly, the novel Reading Tendency Index provides an estimation of an individual\u27s preferred strategy for single word reading without the influence of variable processing speeds. The Index corresponds with predictable neural activations and has implications for instructional and remediation practices

Deep Space Network information system architecture study

The purpose of this article is to describe an architecture for the Deep Space Network (DSN) information system in the years 2000-2010 and to provide guidelines for its evolution during the 1990s. The study scope is defined to be from the front-end areas at the antennas to the end users (spacecraft teams, principal investigators, archival storage systems, and non-NASA partners). The architectural vision provides guidance for major DSN implementation efforts during the next decade. A strong motivation for the study is an expected dramatic improvement in information-systems technologies, such as the following: computer processing, automation technology (including knowledge-based systems), networking and data transport, software and hardware engineering, and human-interface technology. The proposed Ground Information System has the following major features: unified architecture from the front-end area to the end user; open-systems standards to achieve interoperability; DSN production of level 0 data; delivery of level 0 data from the Deep Space Communications Complex, if desired; dedicated telemetry processors for each receiver; security against unauthorized access and errors; and highly automated monitor and control