Fast algorithms for retiming large digital circuits

The increasing complexity of VLSI systems and shrinking time to market requirements demand good optimization tools capable of handling large circuits. Retiming is a powerful transformation that preserves functionality, and can be used to optimize sequential circuits for a wide range of objective functions by judiciously relocating the memory elements. Leiserson and Saxe, who introduced the concept, presented algorithms for period optimization (minperiod retiming) and area optimization (minarea retiming). The ASTRA algorithm proposed an alternative view of retiming using the equivalence between retiming and clock skew optimization;The first part of this thesis defines the relationship between the Leiserson-Saxe and the ASTRA approaches and utilizes it for efficient minarea retiming of large circuits. The new algorithm, Minaret, uses the same linear program formulation as the Leiserson-Saxe approach. The underlying philosophy of the ASTRA approach is incorporated to reduce the number of variables and constraints in this linear program. This allows minarea retiming of circuits with over 56,000 gates in under fifteen minutes;The movement of flip-flops in control logic changes the state encoding of finite state machines, requiring the preservation of initial (reset) states. In the next part of this work the problem of minimizing the number of flip-flops in control logic subject to a specified clock period and with the guarantee of an equivalent initial state, is formulated as a mixed integer linear program. Bounds on the retiming variables are used to guarantee an equivalent initial state in the retimed circuit. These bounds lead to a simple method for calculating an equivalent initial state for the retimed circuit;The transparent nature of level sensitive latches enables level-clocked circuits to operate faster and require less area. However, this transparency makes the operation of level-clocked circuits very complex, and optimization of level-clocked circuits is a difficult task. This thesis also presents efficient algorithms for retiming large level-clocked circuits. The relationship between retiming and clock skew optimization for level-clocked circuits is defined and utilized to develop efficient retiming algorithms for period and area optimization. Using these algorithms a circuit with 56,000 gates could be retimed for minimum period in under twenty seconds and for minimum area in under 1.5 hours

Retiming and Resynthesis with Sweep Are Complete for Sequential Transformation

Abstract-There is a long history of investigations and debates on whether a sequence of retiming and resynthesis is complete for all sequential transformations (on steady states). It has been shown that the sweep operation, which adds or removes registers not used by any output, is necessary for some sequential transformations. However, it is an open question whether retiming and resynthesis with sweep are complete. This paper proves that the operations are complete, but with one caveat: at least one resynthesis operation needs to look through the register boundary into the logic of previous cycle. We showed that this one-cycle reachability is required for retiming and resynthesis to be complete for re-encodings with different code length. This requirement comes from the fact that Boolean circuit is used for a discrete function thus its range needs to be computed by a traversal of the circuit. In theory, five operations in the order of sweep, resynthesis, retiming, resynthesis, and sweep are already complete. However, some practical limitations on resynthesis must be considered. The complexity of retiming and resynthesis verification is also discussed

An efficient incremental algorithm for min-area retiming

As one of the most effective sequential optimization tech-niques, retiming is a structural transformation that relocates flip-flops in a circuit without changing its functionality. The min-area retiming problem seeks a solution with the mini-mum flip-flop area (or number) under a given clock period. Even though having polynomial runtime, the best existing algorithms for this problem still need to first construct a dense path graph and then find a min-cost network flow on it, thus incur huge storage and time expenses for large cir-cuits. Recently, provable incremental algorithms have been discovered for min-period retiming, and heuristic incremen-tal algorithms have been proposed for min-area retiming. However, given the complexity of the problem, min-area re-timing is still resisting an efficient provable incremental algo-rithm. In this paper, we fill the gap by presenting an efficient algorithm to solve the min-area retiming problem incremen-tally and optimally. Contrary to existing approaches, no dense path graph is constructed; only the active timing con-straints are dynamically generated in the algorithm. Exper-imental results show that the total runtime of our algorithm for all the benchmarks is at least 60 × faster than the best existing approach

The Development of Labial Clusters in the Aśokan Rock Edicts

The original range of consonant clusters in Indo-Aryan reduced significantly over time, developing into geminates, homorganic nasal-stop clusters, and sonorant-h clusters in Middle Indo-Aryan. Early Middle Indo-Aryan, as represented in the Aśokan inscriptions, however, still maintained the original clusters, or what appear to be transitional stages of the extensive changes. Salient among those cluster changes that are observed in the Aśokan inscriptions are the changes tm, tv> tp and dv > db in Girnār in the west; sm, sv > sp in Shāhbāzgaṛhī and Mānsehrā in the north-west; and mh > mbh in Kālsī in the north and in Dhaulī and Jaugaḍa in the east. The idiosyncratic nature of these changes lies in the development of a stop from m or v, where the more usual changes would be loss or assimilation of m after a stop and of v after a stop or a sibilant, while sm and hm would normally change to mh. This paper examines the manner assimilation of the “labial” clusters (that is, the clusters with m or v that normally do not incur assimilation of the adjacent consonant) in the Aśokan Rock Edicts. It discusses the conditions, the motivation, the course of the change of m/v to a labial stop, and the dialectal differences associated with this change

Conformance relations and hyperproperties for doping detection in time and space

We present a novel and generalised notion of doping cleanness for cyber-physical systems that allows for perturbing the inputs and observing the perturbed outputs both in the time- and value-domains. We instantiate our definition using existing notions of conformance for cyber-physical systems. As a formal basis for monitoring conformance-based cleanness, we develop the temporal logic HyperSTL*, an extension of Signal Temporal Logics with trace quantifiers and a freeze operator. We show that our generalised definitions are essential in a data-driven method for doping detection and apply our definitions to a case study concerning diesel emission tests

Resurgence of interest in the hemodynamic alterations of advanced heart failure

Historically, cardiac insufficiency has always being allocated to be the culprit lesion of the heart failure syndrome. However, contemporary heart failure pharmacotherapy solely focuses on preservation of neurohormonal homeostasis. The research described in this manuscript is the result of thorough investigation of the hemodynamic alterations of hundreds of patients admitted for advanced decompensated heart failure (ADHF). Firstly, our data suggest that progressive cardiac insufficiency and hemodynamic derangements assessed through invasive hemodynamic monitoring, are still contributing to short- and long-term compromise, and this independent of race or gender. In addition, we demonstrated that restoring an optimal hemodynamic balance with add-on afterload reduction provides incremental intermediate- and long-term benefits over evidence based neurohormonal blockade alone. Indeed parental vasodilator therapy with sodium nitroprusside can be safely administered to achieve more hemodynamic improvement in patients presenting with ADHF. In addition, the institution of a more aggressive oral vasodilator regimen with isosorbide diniatrate / hydralazine over standard neurohormonal antagonists at the time of discharge after an episode of ADHF can safely maintain these hemodynamic improvements leading to improved outcomes. Another novel insight comes from the notice that venous congestion and raised intra-abdominal pressure, more than impaired cardiac output, seem to be related to the development of worsening renal function in patients admitted with ADHF. Treatment strategies with the aim of better renal preservation should therefore focus how to safely reduce this renal venous congestion with diuretic therapy, ultrafiltration or paracentesis whenever indicated. Finally, we demonstrated that cardiac resynchronization therapy (CRT) really acts as a novel "hemodynamic therapy" for advanced heart failure patients even in the patient population previously categorized as "non-responders". Moreover, we have proven that the phenotypic improvement in heart failure status after prolonged CRT is paralleled by a reversed left ventricualr remodeling and recovery of left ventricular contractility. Thus, prolonged (hemodynamic) unloading of the heart will lead to physiological changes on the myocyte level in hearts once destined to only further deteriorate

Tax Policy and Corporate Saving

macroeconomics,corporate saving, tax policy

Stereoscopic Cinema

International audienceStereoscopic cinema has seen a surge of activity in recent years, and for the first time all of the major Hollywood studios released 3-D movies in 2009. This is happening alongside the adoption of 3-D technology for sports broadcasting, and the arrival of 3-D TVs for the home. Two previous attempts to introduce 3-D cinema in the 1950s and the 1980s failed because the contemporary technology was immature and resulted in viewer discomfort. But current technologies – such as accurately-adjustable 3-D camera rigs with onboard computers to automatically inform a camera operator of inappropriate stereoscopic shots, digital processing for post-shooting rectification of the 3-D imagery, digital projectors for accurate positioning of the two stereo projections on the cinema screen, and polarized silver screens to reduce cross-talk between the viewers left- and right-eyes – mean that the viewer experience is at a much higher level of quality than in the past. Even so, creation of stereoscopic cinema is an open, active research area, and there are many challenges from acquisition to post-production to automatic adaptation for different-sized display. This chapter describes the current state-of-the-art in stereoscopic cinema, and directions of future work