Cross-Layer Automated Hardware Design for Accuracy-Configurable Approximate Computing

Approximate Computing trades off computation accuracy against performance or energy efficiency. It is a design paradigm that arose in the last decade as an answer to diminishing returns from Dennard\u27s scaling and a shift in the prominent workloads. A range of modern workloads, categorized mainly as recognition, mining, and synthesis, features an inherent tolerance to approximations. Their characteristics, such as redundancies in their input data and robust-to-noise algorithms, allow them to produce outputs of acceptable quality, despite an approximation in some of their computations. Approximate Computing leverages the application tolerance by relaxing the exactness in computation towards primary design goals of increasing performance or improving energy efficiency. Existing techniques span across the abstraction layers of computer systems where cross-layer techniques are shown to offer a larger design space and yield higher savings. Currently, the majority of the existing work aims at meeting a single accuracy. The extent of approximation tolerance, however, significantly varies with a change in input characteristics and applications. In this dissertation, methods and implementations are presented for cross-layer and automated design of accuracy-configurable Approximate Computing to maximally exploit the performance and energy benefits. In particular, this dissertation addresses the following challenges and introduces novel contributions: A main Approximate Computing category in hardware is to scale either voltage or frequency beyond the safe limits for power or performance benefits, respectively. The rationale is that timing errors would be gradual and for an initial range tolerable. This scaling enables a fine-grain accuracy-configurability by varying the timing error occurrence. However, conventional synthesis tools aim at meeting a single delay for all paths within the circuit. Subsequently, with voltage or frequency scaling, either all paths succeed, or a large number of paths fail simultaneously, with a steep increase in error rate and magnitude. This dissertation presents an automated method for minimizing path delays by individually constraining the primary outputs of combinational circuits. As a result, it reduces the number of failing paths and makes the timing errors significantly more gradual, and also rarer and smaller on average. Additionally, it reveals that delays can be significantly reduced towards the least significant bit (LSB) and allows operating at a higher frequency when small operands are computed. Precision scaling, i.e., reducing the representation of data and its accuracy is widely used in multiple abstraction layers in Approximate Computing. Reducing data precision also reduces the transistor toggles, and therefore the dynamic power consumption. Application and architecture level precision scaling results in using only LSBs of the circuit. Arithmetic circuits often have less complexity and logic depth in LSBs compared to most significant bits (MSB). To take advantage of this circuit property, a delay-altering synthesis methodology is proposed. The method finds energy-optimal delay values under configurable precision usage and assigns them to primary outputs used for different precisions. Thereby, it enables dynamic frequency-precision scalable circuits for energy efficiency. Within the hardware architecture, it is possible to instantiate multiple units with the same functionality with different fixed approximation levels, where each block benefits from having fewer transistors and also synthesis relaxations. These blocks can be selected dynamically and thus allow to configure the accuracy during runtime. Instantiating such approximate blocks can be a lower dynamic power but higher area and leakage cost alternative to the current state-of-the-art gating mechanisms which switch off a group of paths in the circuit to reduce the toggling activity. Jointly, instantiating multiple blocks and gating mechanisms produce a large design space of accuracy-configurable hardware, where energy-optimal solutions require a cross-layer search in architecture and circuit levels. To that end, an approximate hardware synthesis methodology is proposed with joint optimizations in architecture and circuit for dynamic accuracy scaling, and thereby it enables energy vs. area trade-offs

Designs of devices : the vacuum aspirator and American abortion technology

In 1965, 71% of legal abortions in the United States were performed using the surgical procedure of dilation and curettage. By 1972, a mere seven years later, approximately the same percentage (72.6%) of legal abortions in the United States were performed using a completely new abortion technology: the electrical vacuum aspirator. This article examines why, in less than a decade, electric vacuum suction became American physicians' abortion technology of choice. It focuses on factors such as political and professional feasibility (the technology was able to complement the decriminalization of abortion in the US, and the interests, abilities, commitments, and personal beliefs of physicians); clinical compatibility (it met physician/patient criteria such as safety, simplicity and effectiveness); and economic viability (it was able to adapt to market factors such as production, cost, supply/demand, availability, and distribution)

Review: Robert Azzarello, Three Hundred Years of Decadence: New Orleans Literature and the Transatlantic World (Baton Rouge: Louisiana State University Press, 2019)

As Robert Azzarello expresses in Three Hundred Years of Decadence, when embodied in human form, decadence evokes a tableau of pleasure, indulgence, and excess – a decadent is someone ‘who has had too much – too much nicotine or caffeine, too much liquor or morphine, too much literature or philosophy or art – and is thus reduced to a state of being that seems to oscillate between comatose and enlightened.’ The decadent individual is almost always a late nineteenth-century western European, a Parisian or Londoner who has read ‘too much’ Baudelaire or Wilde and consumed ‘too much’ absinthe. However, as Azzarello argues in this groundbreaking work, the decadent tradition also has a long, if yet unexcavated, tradition in the United States. To date, most of what has been studied focuses on a coterie of fin-de-siècle, transatlantic American poets, novelists and critics including James Huneker, Vance Thompson, Robert William Chambers, Vincent O’Sullivan, David Park Barnitz, and brothers Edgar and Francis Saltus, all of whom spent time in Paris and London at the turn of the twentieth century and were heavily influenced by Joris-Karl Huysmans, Charles Baudelaire, Oscar Wilde, and Henry James. After returning to the United States, they attempted to popularize the decadent tradition through their own works, but were generally unsuccessful. Today, these American decadents remain unknown and understudied, with the exception of a few contributions to the secondary literature such as David Weir’s books, Decadence and the Making of Modernism (1995) and Decadent Culture in the United States: Art and Literature against the American Grain, 1890–1926 (2008)

Designs of devices: The vacuum aspirator and American abortion technology

In 1965, 71% of legal abortions in the United States were performed using the surgical procedure of dilation and curettage. By 1972, a mere seven years later, approximately the same percentage (72.6%) of legal abortions in the United States were performed using a completely new abortion technology: the electrical vacuum aspirator. This article examines why, in less than a decade, electric vacuum suction became American physicians’ abortion technology of choice. It focuses on factors such as political and professional feasibility (the technology was able to complement the decriminalization of abortion in the US, and the interests, abilities, commitments, and personal beliefs of physicians); clinical compatibility (it met physician/patient criteria such as safety, simplicity and effectiveness); and economic viability (it was able to adapt to market factors such as production, cost, supply/demand, availability, and distribution)

“We’re what we are because of the Past”: History, Memory, Nostalgia, and Identity in Walter Sullivan’s The Long, Long Love

Walter Sullivan (1924–2006), a Nashville, Tennessee native who spent most of his academic and professional life at Vanderbilt University, is generally considered by critics as a literary descendent of the first two generations of Fugitive-Agrarians and the Southern Renaissance to which they belong. This essay seeks to position Sullivan’s second, largely forgotten novel, The Long, Long Love as part of the postagrarian, post-Renaissance, postmodern, and post-southern American intellectual reevaluation of the South that questions tradition through an assertion of “pro–New South, pro–urban, and pro–capitalist” values and thoroughly reconsiders Civil War “truths,” myths, history, and memory

An asymptotic formula of cosine power sums

In the paper, the authors find several accurate approximations of some cosine power sums and present an asymptotic formula for these cosine power sums

CNC İşleme Merkezlerinde Hataların İş Esaslı Yaklaşımla Düzeltilmesi

Bu çalışmada, endüstri 4.0 uygulamalarında öne çıkan sıfır hata konseptine göre işparçasının işlenmesi sırasında düşük maliyetli kompanzasyon (telafi) metodu geliştirilmiştir. Yeni yöntem sayesinde, delik delme esnasında oluşan eksen hataları tespit edilmiş ve referans mastar blokları yardımıyla doğrulama faktörü bulunmuştur. Bu faktör kullanılarak, hata miktarı oranında nümerik kontrol (NC) kodları güncellenmiştir. Elde edilen sonuçlara göre, makine üzerine takılı ölçme probu yardımıyla doğru ve izlenebilir ölçüm yapılabildiği sonucuna ulaşılmıştır. Bu yöntemin düşük bir maliyet ile hassas parça imalatında kullanılabilir olduğu sonucuna varılmıştır. Delik mesafesi 500 mm için 55 μm olan tezgâhtan kaynaklanan eksen hatasının, yeni yöntemle ± 10 µm tolerans aralığında gerçekleştiği tespit edilmiştir. Kompanzasyon yöntemi yardımıyla eksen sapma değerleri %81 oranında iyileştirilmiştir

AdvManuNet: a networking project on metrology for advanced manufacturing

The networking project AdvManuNet has been started recently to accelerate the process of establishing an European Metrology Network (EMN) on Advanced Manufacturing. EMNs are intended by EURAMET, the association of metrology institutes in Europe, to provide a sustainable structure for ongoing stakeholder interaction in different thematic areas. Advanced manufacturing has been identified by the European Commission (EC) as one of six Key Enabling Technologies (KETs) with applications in multiple industries. Various EURAMET projects have partly addressed metrology needs for advanced manufacturing. However, a high-level coordination of the metrology community is currently absent and limits the impact of metrology developments on advanced manufacturing. AdvManuNet will address these limits by establishing a single hub for stakeholder consultation, a knowledge base on research results, and a strategic agenda for research and training to push forward advanced manufacturing and related KETs and strengthen Europe’s position in advanced manufacturing via the EMN