Bidirectional data flow analysis

Partial redundancy elimination (PRE) is an interesting compiler optimization because of its effectiveness and generality. Among many PRE algorithms, the one in static single assignment form (SSAPRE) has benefits over other bit-vector-based PRE algorithms. It preserves the properties of the SSA form after PRE and exploits the sparsity of the SSA form, resulting in reduced analysis and optimization time. This paper presents a practical improvement of the SSAPRE algorithm that further reduces the analysis and optimization time. The underlying idea is removing unnecessary Φ’s during the Φ-Insertion phase that is the first step of SSAPRE. We classify the expressions into three categories: confined expressions, local expressions, and the others. We show that unnecessary Φ’s for confined and local expressions can be easily detected and removed. We implement our locality-based SSAPRE algorithm in a C compiler and evaluate its effectiveness with 20 applications from SPEC benchmark suites. In our measurements, on average 91% of Φ’s identified by the original demand-driven SSAPRE algorithm are unnecessary for PRE. Pruning these unnecessary Φ’s in the Φ-Insertion phase makes our locality-based SSAPRE algorithm 1.8 times faster, on average, than the original SSAPRE algorithm.

Instruction schedulers employ code motion as a means of instruction reordering to enable scheduling of instructions at points where the resources required for their execution are available. In addition, driven by the profiling data, schedulers take advantage of predication and speculation for aggressive code motion across conditional branches. Optimization algorithms for partial dead code elimination (PDE) and partial redundancy elimination (PRE) employ code sinking and hoisting to enable optimization. However, unlike instruction scheduling, these optimization algorithms are unaware of resource availability and are incapable of exploiting profiling information, speculation, and predication. In this paper we develop data flow algorithms for performing the above optimizations with the following characteristics: (i) opportunities for PRE and PDE enabled by hoisting and sinking are exploited; (ii) hoisting and sinking of a code statement is driven by availability of functional unit resources; (iii) predication and speculation is incorporated to allow aggressive hoisting and sinking; and (iv) path profile information guides predication and speculation to enable optimization.

Mass flow rate through a horizontal opening at small pressure differences

This study investigated the influence of a cyclist on crowd behaviors on a shared road. A series of mixed traffic experiments of a cyclist and a crowd of pedestrians were conducted in a circular wide track under different densities and moving directions. The influence of the cyclist on the fundamental diagram of pedestrians showed a clear difference under unidirectional and bidirectional scenarios. The cyclist restricted the pedestrian flow evidently in the unidirectional flow, while in bidirectional flow, a critical density around 0.9 ped m−2 was observed, where the restriction on the motion of the crowd was not noticeable unless the critical density was reached. The speed of the cyclist also depended on the relative moving direction, but the discrepancy became negligible when the following effect was eliminated. The lane formation was quantitatively analyzed with Otsu’s method. The results showed that the formed lanes were more concentrated in bidirectional flow than unidirectional flow. When two lanes were formed, the distances between the lanes were larger in unidirectional flow. These differences could be explained by the cognition difference of pedestrians in mixed traffic under unidirectional and bidirectional scenarios. It was observed that a major effect of the cyclist on the crowd behavioral mechanism was the generation of backward propagated density waves. A Y-shaped pattern for the formation of high-density clusters was discovered, which implied that stable high-density clusters were likely to form as the forward propagated and backward propagated density waves merged. Moreover, in bidirectional flow, the generated backward propagated density wave could also promote the fading of stable high-density clusters by reducing the heterogeneity of density distribution. Our study helps to achieve a better understanding and modeling of the dynamics of pedestrian–cyclist in mixed traffic.

When analyzing programs for value recomputation, one faces the problem of naming the value that flows between equivalent computations with different lexical names. This paper presents a data-flow analysis framework that overcomes this problem by synthesizing a name space tailored for tracing the values whose flow is of interest to a given data-flow problem. Furthermore, to exploit recomputation of a value with multiple, synonymous names, path-sensitive value numbering on the synthetic name space is developed. Optimizations that rely on value flow to detect redundant computations, such as partial redundancy elimination and constant propagation, become more powerful when phrased in our framework.The framework is built on a new program representation called Value Name Graph (VNG) which gains its power from integrating three orthogonal techniques: symbolic back-substitution, value numbering, and data-flow analysis. Our experiments with the implementation show that analysis on the VNG is practical in both time and space.

Partial Redundancy Elimination (PRE) is a general scheme for suppressing partial redundancies which encompasses traditional optimizations like loop invariant code motion and redundant code elimination. In this paper we address the problem of performing this optimization interprocedurally. We use interprocedural partial redundancy elimination for placement of communication and communication preprocessing statements while compiling for distributed memory parallel machines.

Partial redundancy elimination (PRE) is a key technology for modern compilers. However traditional approaches are conservative and fail to exploit many opportunities for optimization. New PRE approaches which greatly increase the number of eliminated redundancies have been developed. However, they either cause the code size to explode or they cannot handle statements with side-effects. In this paper we describe a predicated partial redundancy elimination (PPRE) approach which can potentially remove all partial redundancies. To avoid performance overheads caused by predication, PPRE is applied selectively based on a cost model. The cost analysis presented in the paper utilizes probabilistic data-flow information to decide whether PPRE is profitable for each instance of a partially redundant computation. Refinements of the basic PPRE transformation are described in detail. In contrast to some other approaches our transformation is strictly semantics preserving.

The phase-mapping method of phase-contrast magnetic resonance angiography is shown to be based on an implicit assumption that the intravoxel velocity distribution is symmetric about its mean velocity. The effect of asymmetric distributions on the accuracy of quantitative average velocity measurements is determined analytically and verified experimentally. An explicit formulation is developed for the estimated average velocity in a voxel as a function of the true average velocity and the asymmetry of the distribution about the true average velocity. Worst-case distributions are determined for unidirectional and bidirectional flow, and the special case of laminar flow is also investigated. Computer simulations and phantom imaging experiments demonstrate the accuracy of the analysis. For voxels with unidirectional flow, the phase-mapping method produces accurate estimates of average velocity, while results for bidirectional flow indicate possible large errors unless the aliasing velocity is increased, which decreases the signal-to-noise ratio in the resultant velocity map image.

Objective: To assess endoscopically the hemodynamic function of arterioarterial (AA) anastomoses in twin-twin transfusion syndrome (TTTS) and monochorionic selective intrauterine growth restriction(IUGR).Materials and methods: The videotapes of TTTS and IUGR patients undergoing laser surgery between July 1997 and December 2001 were reviewed for the presence of AA anastomoses. The hemodynamicequator was defined as the site within the AA anastomosis with color flashing. AA anastomoses were classified as having unidirectional flow, having bi-directional flow, or being non-functional, dependingon whether the hemodynamic equator reached a returning vein to one, both, or neither twin, respectively. TTTS was classified in stages as previously described.Results: AA anastomoses were presentin 35/183 (19.1%) of TTTS and in 12/24 (50%) IUGR patients. Of these, the hemodynamic equator was visible in 8/35 (22.8%) TTTS patients (all in stage III, and mostly in atypical stage III) and in 6/12 (50%)IUGR patients (overall 14/47, 29.8%). Of the 14 patients with a visible hemodynamic equator, 13 (92.8%) AA anastomoses showed unidirectional (9/13, 69.2% from the smaller to the larger twin) flow, and only1/14 (7.1%) showed bi-directional flow.Conclusion: The hemodynamic equator is visible in approximately 30% of patients with AA anastomoses. Within this group, most AA anastomoses behave as functionalarteriovenous anastomoses, and the direction of flow can be from the smaller to the larger twin or vice versa. The data suggest a correlation between sonographic findings and placental vascular design,also implying possible interfetal oxygenation differences. Further assessment of the functional behavior of AA anastomoses is warranted to understand the pathophysiology of TTTS and selective IUGR.

The adoption of Digital Twins (DTw) related technologies in the Architecture, Engineering, Construction, and Operations (AECO) sector has enhanced data-driven decision-making through bi-directional data flows and real-time analytics. However, the risk of creating new data silos and interoperability hurdles with other technologies and initiatives persist. To unlock the full potential of DTw, integration with broader digital initiatives – such as Digital Building Logbooks and Digital Product Passports – is essential. Addressing these challenges requires a System-of-Systems (SoS) approach and coordinated processes. This research explores the transition towards a SoS approach in the built environment sector. A qualitative methodology was employed, using co-creation workshop with industry professionals, software providers, and academic experts from diverse regions. The data gathered were analyzed using grounded theory, leading to the development of a scalable framework for DTw solutions. This study introduces the Define-Wire-Engineer-Leverage-Transfer (DWELT) framework, designed to support organizations in effectively implementing DTw through a SoS approach.

Diversity of subsystems in the organization can lead towards bad business results. Many companies decide to patch their business system with multiple subsystems which are usually not interoperable. Along with that, organizations have the dilemma of deciding whether to implement best-of-breed or one vendor solution. There is no correct answer to the dilemma. The outcome of the dilemma depends on each organization individually based on their analysis and needs. This article analyzes how to overcome data inconsistency caused by patching the business system and presents an approach to the synchronization of different databases to the Cloud. Usage of database synchronization tools to unify data in the Cloud is practical for mature organizations which aim to establish data consistency. The goal of this article is to consider some tools for database synchronization and to choose one for the practical example considering the known constraints. In the approach, we used few different databases to verify its compliance with chosen synchronization tool. The approach is based on practical example where couple of databases are synchronized to the Cloud ensuring the data consistency and bidirectional data flow. The solution includes chosen tool and the recommendation on how to ensure flawless data integration in the Cloud. Tests of synchronization duration with chosen databases and row quantities are conducted and analyzed at the end of the article.

Systolic array description in F 2

In recent years, wind plants have undergone major changes due to new technologies developed for smart grids (SG). For its success, it becomes necessary the use of modern information and telecommunication infrastructure with bidirectional data flow. In Brazil, due to the high penetration of data networks based on GSM technology (Global System Mobile), such as GPRS (General Packet Radio Service) and EGPRS (Enhanced GPRS), it has attracted the interest of energy companies to carry out the tasks of measurement, monitoring, and control in SG. The use of cellular technology enables at first a significant reduction in the SG deployment costs while providing reliability and security of the information. In this context, the use of a cellular network for monitoring and control data sharing in intelligent wind farms has recently aroused great interest. This work proposes the analysis of a wireless control system based on GPRS and EGPRS data services for variable-speed squirrel-cage induction generators (SCIG) connected to the power grid. The wireless communication system is employed to send the reference power signals to the SCIG controller with the necessary reliability to ensure the power quality provided by the wind turbine. The performance of the proposed system is evaluated by several simulations and tests.

In this paper two railway electro-dynamic centralization installations (RECI) supervising system are introduced. Our RECI supervising systems take into account the real state of the installations, irrespective to the logic of the railway station central post of the railway station. The first system consists of a computer, an interface board, and the software programs. The interface has bi-directional data flow between the installation and computer. The computer is connected, through an Intranet network, to the Railway Circulation Regulator (RCR) and to other similar computers allocated in the area of the same RCR. The second system uses programmable logic controllers (PLC) for extending the control to a larger number of RECI units. Further research directions are also mentioned in the paper.

Seafloor observatories enable long term, continuous and multidisciplinary observations, promising major breakthroughs in marine environment research. The effort to remotely control in situ multidisciplinary equipment performing individual and cooperative tasks is both a challenge and a guarantee for the stable operations of functional observatories. With China starting to establish ocean observatory sensor networks, in this study we describe a monitoring system for cabled observatories in the East China Sea (ESOMS) that enables this effort in a plug and play way. An information oriented monitoring architecture for ESOMS was first introduced, derived from a layered control model for ocean observatory sensor network. The architecture contained three components and enabled bidirectional information flow of observation data and commands, based on which architecture components were designed to enable plug-and-play control within related model layers. A control method enabled by general junction box (GJB) and ocean sensor markup language (OSML) was thus proposed as the plug-and-play solution for implementing ESOMS. The GJB-OSML enabled control method (GOE Control Method) mainly actualized two processes, one of which was that the in situ GJB interfaced and represented every attached sensor as a Sensing Endpoint in the cabled observatory network. The other process was that the remote ESOMS utilized the same IP/Port related information modeled by OSML to create/operate a Function Node acted as agent of the in situ sensor. A case study for using ESOMS in the Xiaoqushan Seafloor Observatory was finally presented to prove its performance and applicability. Given this successful engineering trial, the ESOMS design and implementation could be applicable and beneficial for similar efforts in future construction of seafloor observatory network both at home and abroad.