Optimization of range checking

We introduce a new approach, Dynamic Common Sub-expression Elimination (CSE), that dynamically eliminates common sub- expressions based on new opportunities created during scheduling of control-intensive designs. Classical CSE techniques fail to eliminate several common sub-expressions in control-intensive designs due to the presence of a complex mix of control and data-flow. Aggressive speculative code motions employed to schedule control-intensive designs often re-order, speculate and duplicate operations, hence changing the control flow between the operations with common sub-expressions. This leads to new opportunities for applying CSE dynamically. We have implemented dynamic CSE in a high-level synthesis framework called Spark and present results for experiments performed using various combinations of CSE and dynamic CSE. The benchmarks used consist of four functional blocks derived from two moderately complex industrial-strength applications, namely, MPEG-1 and the GIMP image processing tool. Our dynamic CSE techniques result in improvements of up to 22% in the controller size and up to 31% in performance; easily surpassing the improvements obtained by the traditional CSE approach. We also observe an unexpected (and significant) reduction in the number of registers using our approach.

Translation Validation is an approach of ensuring compilation correctness in which each compiler run is followed by a validation pass that proves that the target code produced by the compiler is a correct translation (implementation) of the source code. It has been previously shown that the problem of translation validation can be reduced to checking if a single system - the corss-product of the source and target, satisfies a specific property. In this paper, we show how to adapt the existing program analysis techniques in the setting of translation validation. In addition, we present a novel invariant generation algorithm which strengthens our analysis when the input programs contain dynamically allocated data structures. Finally, we report on the prototype tool that applies the developed methodology to verification of the LLVM compiler. The tool handles many of the classical intraprocedural compiler optimizations such as constant folding, reassociation, common subexpression elimination, code motion, dead code elimination, and others.

This paper presents a unified framework for program optimization which subsumes (i) Loop invariant code motion, (ii) Common subexpression elimination, and (iii) Strength reduction. Use of this framework is shown to eliminate the control flow analysis costs and to widen the scope of conventional strength reduction.

ABSTRACTThis paper presents an efficient design method for a digital multiplierless two-channel filterbank using the shifted-Chebyshev polynomials and common sub-expression elimination (CSE) algorithm for reducing hardware requirements such as adders and multipliers. For designing a two-channel filterbank, the design problem is constructed as minimization of integral mean square error between the desired and designed response of a prototype filter in the passband and stopband. For controlling the performance in passband and stopband, two parameters (KP, and KS) are used, whose optimum values are determined by swam optimization techniques such as differential evolution algorithm, artificial bee colony optimization, particle swarm optimizations, cuckoo search algorithm and hybrid method using a fitness function, constructed by perfect reconstruction condition of a filterbank. The number of polynomials used for approximation depends upon the order of a prototype filter. A new hybrid CSE is proposed for further reduction of hardware requirement. A comparative study of various CSE techniques such as horizontal, vertical and proposed hybrid CSE is also made. Numerical examples illustrate the effectiveness of the proposed algorithm in the reduction of adders with comparisons accomplished using existing methods. It has been found that almost 43% adder gain can be achieved when a filter is designed with N = 32 and wordlength (WL) as 12 using proposed methodology.

Electrical and impedance properties of composites: Volcanic basalt rocks

Objective:To evaluate the frequency characteristics of semicircular canal injury in patients with vestibular neuritis. Method:Fifty-three patients with vestibular neuritis were respectively evaluated by caloric test(CT)，head shaking test(HST),video head impulse test (vHIT),which reflects semicircular canal function in the low, middle, high frequency region. The asymmetric value of CT unilateral semicircular canal reaction (UW), head shaking nystagmus induced by HST, gain value of VHIT (VHIT-G) and presence or absence of saccade (VHIT-S) were used as observation indicators. The data were analyzed by SPSS 17.0 statistical software.The characteristics of the results of the three tests in patients with vestibular neuritis was analyzed and the functional status of the high, middle and low frequency regions of the semicircular canal was evaluated. Result:The positive rates of CT, HST, VHIT-G and VHIT-S in 53 patients with vestibular neuritis were 94.3%（50/53）,75.5%（40/53）,81.1%（43/53）,96.2%（51/53）,respectively. The positive rates of CT, HST, VHIT-G and VHIT-S were 92.9%（26/28）,89.3%（25/28）,92.9%（26/28）,96.4%（27/28）in 28 cases with disease course ≤ 7 days, and the positive rates in 25 patients with disease course >7 days were 96.0%（24/25）,60.0%（15/25）,68.0%（17/25）,96.0%（24/25）,respectively. Compared with the positive rate of each index, CT and VHIT-G (P=0.076), HST and VHIT-G (P=0.480) had no statistical significance. The difference between CT and HST (P=0.015), VHIT-G and VHIT-S(P=0.032) was statistically significant. The positive rates of CT, HST, VHIT-G and VHIT-saccade in patients with course of disease ≤7 days were compared, and there was no significant difference. In patients with disease course >7 days, except HST and VHIT-G, there were statistical differences in other indexes. The correlation test between VHIT-G and VHIT-S：r=-0.437, P=0.006. Conclusion:The vestibular injury in patients with vestibular neuritis showed in a manner of full frequency injury. The multi-frequency detection technique is helpful for the clinical diagnosis of vestibular neuritis, and also can reflect the compensation and recovery of vestibular function.

The conventional program optimization techniques employed by the ILLIAC FORTRAN compiler are general purpose, effective, and efficient. The underlying theory is applicable to FORTRAN and to other high level languages. A unique approach to the gathering of global set and use information about variables as well as careful software engineering of the algorithms has led to the construction of an effective source-to-source optimizer which performs constant propagation, constant computation, common subexpression elimination, reduction in strength, and invariant code motion.

The unconventional design of the ILLIAC-IV requires unconventional optimization techniques. Conventional techniques focus on the program. Since conventional hardware executes one instruction at a time, greater efficiency is obtained by reducing the number of instructions executed. Elimination of common subexpressions and literal computations, removal of locally invariant computations, reduction of operator strength, etc. are all methods of restructuring a program to allow greater efficiency. This focus on the program is not sufficient for the ILLIAC-IV. Efficient use of an array of processors depends upon the data being stored so as to permit parallel execution on many data streams. Further, the inability of each processor to access more than 2K of memory requires the use of routing commands for inter-processor communication. Hence, optimization on an array computer requires restructuring of the data as the primary area of effort. Such restructuring includes, for example, an extension to the skewed storage method which permits any slice of any array to be accessed in parallel and, further, to be aligned with an other slice by a uniform route. (A slice of an n-dimentional array A is the vector {A(c l ,..., c i−l , j, c i+l ,..., c n : m i ≤ j ≤ M i , c k constant}.)

This paper deals with the application of the notion of semantic attributes (as developped by D.E. KNUTH [1]) to generation of optimized code. Taking local elimination of common sub-expressions as a starting point, it is demonstrated by means of an example that meta-compilation by attributes allows semantic formalization of classical optimization algorithms. A redundancy attribute, R+, is defined to play an optimizing role in connection with redundant common sub-expressions during compilation without having to undergo a special treatment.

A bone conduction hearing aid is considered to be useful in aiding the patients with conductive hearing loss or partially mixed hearing loss. However, the bone conduction hearing aid is inferior to a air conduction hearing aid in sound characteristics. The standard for calibrating these hearing aids has not yet established. Little is known about the standard. The vibratory mode of the receiver of the bone conduction hearing aid was analyzed by holographic interferometry. The technique used was time averaged holography with the light source of an argon laser, the wave length of which was 5145 A. In the present study, 6 types of bone conduction hearing aid were used. The input voltage of each receiver was 0.5 to 2.5V. The frequency was 250 to 8, 000Hz. The vibration of the receiver was recorded and reproduced. Further, the vibration was gained and recorded in a free sound field of sound pressure of 80 to 105dB SPL and frequency of 250 to 2, 000Hz and following results were obtained. 1) The frequency of the bone conduction hearing aid was characterized by the peak around 1, 000Hz and a rapid reduction in the region of high frequency. 2) In the region of low frequency of 250Hz or 500Hz, an increase in the output will lead to improvement in the properties of the hearing aid to some extent. However, improvement in the region of high frequency around 8, 000Hz seemed to be difficult. 3) In respect to the vibration pattern of the bone conduction hearing aid, two patterns (hinge-like movement and distortion movement) were observed according to the type of the hearing aid. However, the difference in the pressure on the skull seemed practically insignificant among the hearing aids.

Digital filter banks are extensively used in an SDR channelizer for channelization. The objective of this research work is to design a low computational complexity FIR filter bank for generating sharp transition width channels for SDR. The design of unified and variable bandwidth channels for SDR using the proposed structure is based on the modified IFIR filter structure and cosine modulation technique (CMT). The performance of the proposed structure is demonstrated with the help of an example. The results show that the multiplier complexity of the proposed structure is less than those of other state-of-the art methods. The optimization techniques are incorporated in this work to further reduce the complexity of the proposed structure. With the help of canonical signed digit (CSD), multi-objective artificial bee colony (MOABC) and shift inclusive differential coefficients (SIDC) – common sub-expression elimination (CSE) optimization, the filter used in this structure is made multiplier-less.

The formulation of a Propositional Satisfiability (SAT) problem instance is vital to efficient solving. This has motivated research on preprocessing, and inprocessing techniques where reformulation of a SAT instance is interleaved with solving. Preprocessing and inprocessing are highly effective in extending the reach of SAT solvers, however they necessarily operate on the lowest level representation of the problem, the raw SAT clauses, where higher-level patterns are difficult and/or costly to identify. Our approach is different: rather than reformulate the SAT representation directly, we apply automated reformulations to a higher level representation (a constraint model) of the original problem. Common Subexpression Elimination (CSE) is a family of techniques to improve automatically the formulation of constraint satisfaction problems, which are often highly beneficial when using a conventional constraint solver. In this work we demonstrate that CSE has similar benefits when the reformulated constraint model is encoded to SAT and solved using a state-of-the-art SAT solver. In some cases we observe speed improvements of over 100 times.KeywordsConstraint ModelNegation Normal FormImplied ConstraintCommon Subexpression EliminationGlobal Cardinality ConstraintThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Common subexpression elimination is a well-known compiler optimisation that saves time by avoiding the repetition of the same computation. In lazy functional languages, referential transparency renders the identification of common subexpressions very simple. More common subexpressions can be recognised because they can be of arbitrary type whereas standard common subexpression elimination only shares primitive values. However, because lazy functional languages decouple program structure from data space allocation and control flow, analysing its effects and deciding under which conditions the elimination of a common subexpression is beneficial proves to be quite difficult. We developed and implemented the transformation for the language Haskell by extending the Glasgow Haskell compiler. On real-world programs the transformation showed nearly no effect. The reason is that common subexpressions whose elimination could speed up programs are uncommon in lazy functional languages.KeywordsTransformation RuleCost CentreRepeated ComputationCase ExpressionSafe TypeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

A frequency domain 3 sigma LER characterization methodology combining the standard deviation and power spectral density (PSD) methods is proposed. In the new method, the standard deviation is calculated in the frequency domain instead of the spatial domain as in the conventional method. The power spectrum of the LER is divided into three regions: low frequency (LF), middle frequency (MF) and high frequency (HF) regions. The frequency region definition is based on process visual comparisons. Three standard deviation numbers are used to characterize the LER in the three frequency regions. Pattern wiggling can be detected quantitatively with a wiggling factor which is also proposed in this paper.

Corrosion inhibitors, acting as an effective method at lower operating cost, are often used to protect metallic materials from corrosion. Although many kinds of corrosion inhibitors have been used in circulating cooling water systems, a few papers have been published for introducing the applications of corrosion inhibitors in chloride media. By comparison, it is difficult to develop a novel inhibitor for alloy steels in chloride solutions or sea water. In this paper, a novel corrosion inhibitor for L921A alloy steel in a 3.5% NaCl solution was formulated by weight loss in conjunction with orthogonal tests. The inhibitory efficiency of this novel inhibitor was over 95.0%. It was found by electrochemical polarization that this novel inhibitor was a mixed type of inhibitor which had an ability to improve the pitting corrosion resistance of L921A alloy steel in a 3.5% NaCl solution. EIS spectra showed that L921A alloy steel in a 3.5% NaCl solution was subjected to pitting corrosion, due to that EIS spectrum of L921A alloy steel in a 3.5% NaCl solution was composed of a capacitive loop at high frequency region and an inductive loop at low frequency region. However, EIS spectrum with two time constants consisted of a capacitive loop at high frequency region and a Warburg line at low frequency region when the novel inhibitor was added into a 3.5% NaCl solution. The thickness of inhibitory film increased with increasing immersion time, resulting in the increment of the electrochemical impedance of corrosion process of L921A alloy steel in a 3.5% NaCl solution. Finally, the formation of the inhibitory film was further studied by EDX and XPS technology.