Standard Library Functions Research Articles

Real-Time Implementation of a Frequency Shifter for Enhancement of Heart Sounds Perception on VLIW DSP Platform

Auscultation of heart sounds is important to perform cardiovascular assessment. External noises may limit heart sound perception. In addition, heart sound bandwidth is concentrated at very low frequencies, where the human ear has poor sensitivity. Therefore, the acoustic perception of the operator can be significantly improved by shifting the heart sound spectrum toward higher frequencies. This study proposes a real-time frequency shifter based on the Hilbert transform. Key system components are the Hilbert transformer implemented as a Finite Impulse Response (FIR) filter, and a Direct Digital Frequency Synthesizer (DDFS), which allows agile modification of the frequency shift. The frequency shifter has been implemented on a VLIW Digital Signal Processor (DSP) by devising a novel piecewise quadratic approximation technique for efficient DDFS implementation. The performance has been compared with other DDFS implementations both considering piecewise linear technique and sine/cosine standard library functions of the DSP. Piecewise techniques allow a more than 50% reduction in execution time compared to the DSP library. Piecewise quadratic technique also allows a more than 50% reduction in total required memory size in comparison to the piecewise linear. The theoretical analysis of the dynamic power dissipation exhibits a more than 20% reduction using piecewise techniques with respect to the DSP library. The real-time operation has been also verified on the DSK6713 rapid prototyping board by Texas Instruments C6713 DSP. Audiologic tests have also been performed to assess the actual improvement of heart sound perception. To this aim, heart sound recordings were corrupted by additive white Gaussian noise, crowded street noise, and helicopter noise, with different signal-to-noise ratios. All recordings were collected from public databases. Statistical analyses of the audiological test results confirm that the proposed approach provides a clear improvement in heartbeat perception in noisy environments.

CPFloat: A C Library for Simulating Low-precision Arithmetic

One can simulate low-precision floating-point arithmetic via software by executing each arithmetic operation in hardware and then rounding the result to the desired number of significant bits. For IEEE-compliant formats, rounding requires only standard mathematical library functions, but handling subnormals, underflow, and overflow demands special attention, and numerical errors can cause mathematically correct formulae to behave incorrectly in finite arithmetic. Moreover, the ensuing implementations are not necessarily efficient, as the library functions these techniques build upon are typically designed to handle a broad range of cases and may not be optimized for the specific needs of rounding algorithms. CPFloat is a C library for simulating low-precision arithmetics. It offers efficient routines for rounding, performing mathematical computations, and querying properties of the simulated low-precision format. The software exploits the bit-level floating-point representation of the format in which the numbers are stored and replaces costly library calls with low-level bit manipulations and integer arithmetic. In numerical experiments, the new techniques bring a considerable speedup (typically one order of magnitude or more) over existing alternatives in C, C++, and MATLAB. To our knowledge, CPFloat is currently the most efficient and complete library for experimenting with custom low-precision floating-point arithmetic.

Analysis and optimization of Dual Parallel Partition Sorting with OpenMP

PurposeSorting is a very important algorithm to solve problems in computer science. The most well-known divide and conquer sorting algorithm is quicksort. It starts with dividing the data into subarrays and finally sorting them.Design/methodology/approachIn this paper, the algorithm named Dual Parallel Partition Sorting (DPPSort) is analyzed and optimized. It consists of a partitioning algorithm named Dual Parallel Partition (DPPartition). The DPPartition is analyzed and optimized in this paper and sorted with standard sorting functions named qsort and STLSort which are quicksort, and introsort algorithms, respectively. This algorithm is run on any shared memory/multicore systems. OpenMP library which supports multiprocessing programming is developed to be compatible with C/C++ standard library function. The authors’ algorithm recursively divides an unsorted array into two halves equally in parallel with Lomuto's partitioning and merge without compare-and-swap instructions. Then, qsort/STLSort is executed in parallel while the subarray is smaller than the sorting cutoff.FindingsIn the authors’ experiments, the 4-core Intel i7-6770 with Ubuntu Linux system is implemented. DPPSort is faster than qsort and STLSort up to 6.82× and 5.88× on Uint64 random distributions, respectively.Originality/valueThe authors can improve the performance of the parallel sorting algorithm by reducing the compare-and-swap instructions in the algorithm. This concept can be used to develop related problems to increase speedup of algorithms.

A stratified approach to function fingerprinting in program binaries using diverse features

Fingerprinting individual functions in binary code is useful in many security applications ranging from digital forensic analysis of malware corpora to the detection of critical security vulnerabilities. However, existing approaches for fingerprinting functions are typically not resilient to code transformation methods or the use of different compilers. Moreover, another common weakness with these approaches is that when they report a similarity, they do not provide reverse engineers with any insight into the underlying evidence. In order to bridge this gap, our paper presents Plumeria, an obfuscation-resilient and scalable approach based on a stratified architecture comprised of three layers. The first layer retrieves as many candidates as possible by capturing statistical characteristics, function behavior, and function neighborhood relationships. The second layer then trains a linear conditional random field to learn the correlations between the features of the function and its semantics. This layer is designed to reduce the number of false positives. Finally, the third layer is designed to provide insights into the underlying evidence by collecting the side effects exhibited from the candidates selected by the previous layer. Our study evaluates Plumeria in the context of several scenarios: fingerprinting functions in obfuscated/de-obfuscated binaries; fingerprinting functions across different compilers; fingerprinting various vulnerabilities across compilers and versions; and fingerprinting standard library functions. We then benchmark Plumeria on real-world projects and malware binaries, comparing it with existing state-of-the-art solutions. Our results show that Plumeria outperforms existing solutions, with an average precision of over 89%

Keras2c: A library for converting Keras neural networks to real-time compatible C

With the growth of machine learning models and neural networks in measurement and control systems comes the need to deploy these models in a way that is compatible with existing systems. Existing options for deploying neural networks either introduce very high latency, require expensive and time consuming work to integrate into existing code bases, or only support a very limited subset of model types. We have therefore developed a new method called Keras2c, which is a simple library for converting Keras/TensorFlow neural network models into real-time compatible C code. It supports a wide range of Keras layers and model types including multidimensional convolutions, recurrent layers, multi-input/output models, and shared layers. Keras2c re-implements the core components of Keras/TensorFlow required for predictive forward passes through neural networks in pure C, relying only on standard library functions considered safe for real-time use. The core functionality consists of ∼1500 lines of code, making it lightweight and easy to integrate into existing codebases. Keras2c has been successfully tested in experiments and is currently in use on the plasma control system at the DIII-D National Fusion Facility at General Atomics in San Diego.

Rapid prototyping and numerical identification of feed drive system using hardware-in-loop realization

Nowadays, the virtual manufacturing is proved to be the promising technology to design a completely digital feed drive system. Especially, the initial parameters tuning, tests, error prediction and diagnostics at the actual location of the feed drive system are at a risk of stressing and even damaging the machine tool. This paper presents an analytical identification method of feed drive system based on HILS (Hardware-In-Loop System), allowing a real CNC to be prototyped quickly from standard library functions for feed drive control laws. The main purpose of drive identification outside the CNC is that it may not be performed when the drive is installed in the CNC and user has no access to the internal control structure. So, it is proposed to identify it outside CNC in the proposed HILS on the basis of a comparison of the real object and its nominal dynamic model. The rapid prototyping model can be easily executed for initial parameters tuning, testing and the risk of stressing and damaging the machine tool during the diagnosis can be avoided effectively as well. The methodology is quite general and applicable to linear or ball screw drives, controlled with commonly used controllers. Furthermore, additional CNC modules can easily be prototyped and integrated to this prototype for other research purposes. Experiments were carried out to compare HILS prototyping to the actual CNC systems. The result demonstrates that the real-time feed drive system can be accurately represented by the identified prototype model.

Research on the Security Data Transmission based on Linux

This paper develops system software in application layer based on Linux operating system. Linux operation system in this paper. Different transmission modes are adopted in different parts to improve the transmission efficiency in the network. The data capture encryption method is used for the file data, and the storage transmission method is used for the image data. It designs an identity authentication protocol and key exchange protocol based on digital certificate and digital sign technology, to avoid the sophistication and filch and improve the reliability of the identity authentication and the security of the key exchange. The common algorithms of symmetric encryption, asymmetric encryption and information digest are studied by using OpenSSL standard library function to realize data encryption module of the system.

A Tutorial on Pharmacodynamic Scripting Facility inSimcyp.

The Simcyp Simulator provides a framework for mechanistic Physiologically‐Based Pharmacokinetic/Pharmacodynamic modeling of potentially interacting drugs. It also provides a scripting facility, using the Lua language, for developing customized pharmacodynamic and toxicity models driven by drug concentrations at the site of action. We present an overview of the scripting facility including the scripting language, the editor, and how scripts are embedded within the Simulator. Examples incorporating differential equations and including inter‐individual variability on parameters are presented.

Determinism at Standard-Library Level in TM-Based Applications

Deterministic execution of a multi-threaded application guarantees that threads access shared memory in the same order and the application gives the same output whenever it runs with the same input parameters. Determinism provides repeatability, which helps programmers in testing and debugging. Additionally, transactional memory (TM) simplifies development of multi-threaded applications so that programmers can use transactions (instead of locks) to synchronize accesses to shared memory. However, transactions that call standard library functions have to be serialized, i.e. to be executed as the only running transactions in the system. The serialization enforces an order of threads execution usually different from the one enforced by a system for deterministic multithreading, which causes deadlocks in the application execution. In this paper, we present DeTrans-lib, the first standard C library that provides deterministic execution of TM-based applications at application and standard-library level. DeTrans-lib avoids deadlocks by performing transaction serialization in deterministic order. We evaluate DeTrans-lib with the benchmarks that invoke a standard C library and perform I/O operations.

A method of Level 1 frames-selection based on GPU for new vacuum solar telescope

The sun high resolution imaging observation is the most important way of New Vacuum Solar Telescope (NVST) located in Fuxian Lake of Yunnan. This paper mainly describes the method of the Level 1 data processing of NVST. Currently, the times used by NVST to calculate the 100 images is about 20 s, which is almost 1.7 times of 100 image acquisition time of 12 s. It cant meet the demand of real time processing. In this situation, we have decided to use GPU to process the data. Because the GPU has multi-threading parallelism and a superiority in image processing. We implemented the algorithm by GPU to short the processing time to meet the demand without changing the original algorithm. Thus, it ensures the accuracy of the original operation without affecting the subsequent operation. The experiment includes two main parts, frames-selection method and shift-and-add method. Frames-selection uses speckle interferometry (SI). It selects part of the images with better quality and then shifts-and-adds them. Not all of the image data are required. Usually we only concerned with the necessary part. So in the election process, we only calculated the frequency and the bandwidth. It will highly improve the accuracy of the selected frame. The Fourier transform spent the most time in this experiment. It runs three times in the frame selection and processes second times in the shift-and add. This part of the length of time consuming operation largely determines the efficiency of the program. The CUDA provides the standard library functions, which called CUBLAS and greatly improve the operating efficiency of the program. The library functions CUBLAS provides matrix operations. In this study, most of the matrix operations referenced standard library functions to achieve a large number of image matrix of the parallel arithmetic and other functions. The rest of them used a GPU multi-threading technology. In our experiments, 100 images calibration only takes 0.25 s, GPU runtime also only 0.6 s, the processing time of a single frame is only 4.7 ms. The time of processing image exposure spends only 12 ms. Therefore, it means that in the next frame of the image exposure time, the processing steps of the previous frame image exposure can be completed synchronously. In the current conditions, it meet the demand of real-time processing.

Faster set intersection with SIMD instructions by reducing branch mispredictions

Set intersection is one of the most important operations for many applications such as Web search engines or database management systems. This paper describes our new algorithm to efficiently find set intersections with sorted arrays on modern processors with SIMD instructions and high branch misprediction penalties. Our algorithm efficiently exploits SIMD instructions and can drastically reduce branch mispredictions. Our algorithm extends a merge-based algorithm by reading multiple elements, instead of just one element, from each of two input arrays and compares all of the pairs of elements from the two arrays to find the elements with the same values. The key insight for our improvement is that we can reduce the number of costly hard-to-predict conditional branches by advancing a pointer by more than one element at a time. Although this algorithm increases the total number of comparisons, we can execute these comparisons more efficiently using the SIMD instructions and gain the benefits of the reduced branch misprediction overhead. Our algorithm is suitable to replace existing standard library functions, such as std::set_intersection in C++, thus accelerating many applications, because the algorithm is simple and requires no preprocessing to generate additional data structures. We implemented our algorithm on Xeon and POWER7+. The experimental results show our algorithm outperforms the std::set_intersection implementation delivered with gcc by up to 5.2x using SIMD instructions and by up to 2.1x even without using SIMD instructions for 32-bit and 64-bit integer datasets. Our SIMD algorithm also outperformed an existing algorithm that can leverage SIMD instructions.

Product Line Production Planning Model Based on Genetic Algorithm

At present, iron and steel enterprise develops towards the direction with many procedure, many process, many variety and many specification, and reaches hundreds and thousands of product series and product mix, how to plan, organize and control steel production, production schedule of its product line are key issues. Mixed production plan model of product line can be summed up in a kind of network flow plan. According to the characteristics of network flow plan, the production schedule model of product network flow is established through describing digraph-connected graph of production procedure of iron and steel enterprise. Its goal function is the biggest profit of production of product line, restrain functions are the capacity limiting conditions, the balanced condition of the middle peak point, capacity restrain with supply and sell production and restrain with enterprise procedure process resources. Several key resource production procedure processes are chosen to calculate by using standard library function of the Matlab7.0 genetic algorithm toolbox to program. Penalty function is adopted in the course of getting solution. These parameters of scale of father population, crossover probability, mutation probability and penalty factor are combined and optimized. Results indicate that goal value reach convergence after finish 119 iterative operations. It accords with the actual conditions of this enterprise basically that the optimization solution to production plans of real iron and steel enterprise by using the algorithm

A refined decompiler to generate C code with high readability

SUMMARYAs a key part of reverse engineering, decompilation plays a very important role in software security and maintenance. A number of tools, such as Boomerang and IDA Hex_rays, have been developed to translate executable programs into source code in a relatively high‐level language. Unfortunately, most existing decompilation tools suffer from low accuracy in identifying variables, functions, and composite structures, resulting in poor readability. To address these limitations, we present a practical decompiler called C‐Decompiler for Windows C programs that (i) uses a shadow stack to perform refined data flow analysis, (ii) adopts inter‐basic‐block register propagation to reduce redundant variables, and (iii) recognizes library (i.e., Standard Template Library) functions by signatures. We evaluate and compare the decompilation quality of C‐Decompiler with two existing tools, Boomerang and IDA Hex_rays, considering four aspects: function analysis, variable expansion rate, total percentage reduction, and cyclomatic complexity. Our experimental results show that on average, C‐Decompiler has the highest total percentage reduction of 55.91%, lowest variable expansion rate of 55.79%, and the same cyclomatic complexity as the original source code for each considered application. Furthermore, in our experiments, C‐Decompiler is able to recognize functions with a lower false positive and false negative rate than the other decompilers. A case study and our evaluation results confirm that C‐Decompiler is a practical tool to produce highly readable C‐style code. Copyright © 2012 John Wiley & Sons, Ltd.

Combining Production Planning Model of Product Line Based on Genetic Algorithm

At present, iron and steel enterprise develops towards the direction with many procedure, many process, many variety and many specification, and reaches hundreds and thousands of product series and product mix, how to plan, organize and control steel production, production schedule of its product line is a key issue. Mixed production plan model of product line can be summed up in a kind of network flow plan issue. According to the characteristics of network flow plan issue, the production schedule model of product network flow is established through describing digraph-connected graph of production procedure of iron and steel enterprise. Its goal function is the biggest profit of production of product line, restrain functions are the capacity limiting conditions, the balanced condition of the middle peak point, capacity restrain with supply and sell production and restrain with enterprise procedure process resources. Several key resource production procedure processes are chosen to calculate by using standard library function of the Matlab7.0 genetic algorithm toolbox to program. Penalty function is adopted in the course of getting solution. These parameters of scale of father population, crossover probability, mutation probability and penalty factor are combined and optimized. Results indicate that goal value reach convergence after finish 119 iterative operations. It accords with the actual conditions of this enterprise basically that the optimization solution to production plans of real iron and steel enterprise by using the algorithm.

Quaternion Analysis Tools for Engineering and Scientific Applications

Q UATERNION algebra has found a number of applications for engineering and scientific problems, including fluidmechanics [1], quantum mechanics [2,3], robotics [4,5], and spacecraft attitude control [5,6]. Unfortunately, the literature available for supporting engineering applications is diffuse for matrix applications, as well as virtually nonexistent for handling scalar linear and quadratic equations. Very little general-purpose software is available for computing quaternion math models. This Note fills an unmet need for providing a convenient reference for quaternion calculations relevant to engineering and scientific applications. Equally important, the Note provides a compendium of examples and techniques for evaluating scalar linear and quadratic equations, as well as linear matrix equations, matrix inversion, and eigensolutions. Basic operations are defined for all intrinsic operations ( , , , =, ) and standard software library function (e.g., sin, cos, ln , exp, cosh,a tan, etc.). A comprehensive solution is presented for handling scalar linear equations, in which many special-case solutions are identified. Particular care is given to identifying the equation coefficient conditions required for generating singular solutions. Numerical algorithms are presented for solving scalar quadratic equations. A previously unknown singularity has been identified that has hampered the solution for quadratic equations, and a new algorithm is presented for analytically eliminating the quadratic matrix-valued singularity for solving scalar quadratic equations. Three strategies are presented for handlingN Nmatrix operations: 1) purely N N quaternion operations, 2) dimension-doubling routines using 2N 2N complex operations, and 3) dimensionquadrupling 4N 4N real operations.Many numerical examples are presented in which Quadpack95, a FORTRAN 95/2003 program developed by the author, is used for evaluating all of the quaternion calculations. II. Quaternion Math Models

Tscope: A C library for programming cognitive experiments on the MS Windows platform

Tscope is a C/C+ + programming library designed for programming experiments that run on Windows 2000/XP. It is intended for a public of experimental psychologists with moderate programming skills, who are accustomed to writing their own experimental programs for DOS but have not made the step to Windows-based programming yet. It provides molecular functions for graphics, sound, timing, randomization, and response registration. Together with ANSI-C standard library functions and the powerful C syntax, this set of functions gives the experimenter the opportunity to program virtually any experiment one can come up with. Tscope is completely based on free software, is distributed under the GNU General Public License, and is available at expsy.ugent.be/tscope. An integrated development environment for compiling and running Tscope programs is also freely available.

Virtual Computer Numerical Control System

This paper presents a comprehensive virtual simulation model for CNC systems. The Virtual CNC (VCNC) has a modular architecture, allowing a real CNC to be prototyped quickly from standard library functions for feed drive models, feedback devices, axis control laws, and trajectory interpolation. Additional CNC modules can easily be prototyped and integrated to the VCNC by the user. Various application examples are presented which include the prediction of contour errors, auto-tuning of feed drive controllers, toolpath and feed modification for improved cornering, and rapid identification of closed loop drive dynamics. Detailed experimental verification is presented for each algorithm.

A note on the use of the Lambert W function in the stability analysis of time-delay systems

The Lambert W function is defined to be the multivalued inverse of the function w → w e w = z . This function has been used in an extremely wide variety of applications, including the stability analysis of fractional-order as well as integer-order time-delay systems. The latter application is based on taking the mth power and/or nth root of the transcendental characteristic equation (TCE) and representing the roots of the derived TCE(s) in terms of W functions. In this note, we re-examine such an application of using the Lambert W function through actually computing the root distributions of the derived TCEs of some chosen orders. It is found that the rightmost root of the original TCE is not necessarily a principal branch Lambert W function solution, and that a derived TCE obtained by taking the mth power of the original TCE introduces superfluous roots to the system. With these observations, some deficiencies displayed in the literature (Chen, Y. Q., & Moore, K. L. (2002a). Analytical stability bound for delayed second-order systems with repeating poles using Lambert W function. Automatica, 38(5), 891–895, Chen, Y. Q., & Moore, K. L. (2002b). Analytical stability bound for a class of delayed fractional-order dynamic systems. Nonlinear Dynamics, 29(1–4), 191–200) are pointed out. Moreover, we clarify the correct use of Lambert W function to stability analysis of a class of time-delay systems. This will actually enlarge the application scope of the Lambert W function, which is becoming a standard library function for various commercial symbolic software packages, to time-delay systems.

Automated Generation of High-Order Partial Derivative Models

A standard problem in science and engineering consists of developing mathematics and sensitivity models for complex applications for optimizing a candidate design. A chain rule-based evaluation technique is presented for analytically evaluating partial derivatives of nonlinear functions and differential equations defined by a high-level language. A coordinate embedding strategy is introduced that replaces all scalar variables with higher-dimensional objects. The higher-dimensional objects are defined by a concatenation of the original scalar and its Jacobian, Hessian, and higher-order partials. Exact sensitivity models are recovered for arbitrarily complex mathematical models. An operator-overloading technique is used to define generalized operators for basic and standard library functions. The generalized operators encode the chain rule of calculus and store the results of partial derivative calculations in the artificial dimensions used to redefine the scalar operations. Hidden operations automatically generate and evaluate exact first- through fourth-order partial derivative models, which are accurate to the working precision of the machine. The new algorithm replaces a normally complex, error-prone, time-consuming, and labor-intensive process for producing the partials with an automatic procedure. Module functions encapsulate new data types, and extended mathematic and library functions for handling vector, matrix, and tensor operations. Matrix operations are shown to generalize easily. The algorithm has broad potential for impacting the design and use of mathematical programming tools for applications in science and engineering. Several applications are presented that demonstrate the effectiveness of the methods.

EL/IX 단계 3을 적용한 실시간 운영체제 Qplus-P용 C 표준 라이브러리의 설계 및 구현

디지털 TV, 인터넷 셋탑박스, 인터넷 전화기 등과 같은 정보가전 제품이 속속 등장하면서 이들 제품의 기능을 제어하는데 필수적인 실시간 운영체제 시장이 크게 성장하고 있다. 한국전자통신연구원에서는 소형의 휴대 정보 단말에서부터 디지털 셋탑박스 및 홈 서버까지 다양한 종류의 정보가전 기기에 공통으로 사용될 수 있는 확장 가능한 표준 실시간 운영체제 Qplus-P를 개발하였다. 본 논문에서는 정보가전용 실시간 운영체제 Qplus-P에 탑재되는 C표준 라이브러리의 설계 및 구현에 대해 기술한다. Qplus-PC표준 라이브러리는 레드햇에서 실시간 운영체제 국제 표준으로 제안된 EL/LX 응용 프로그램 인터페이스 단계에 따라 설계되었다. 그리고 Qplus-P 응용 프로그램 수행에 필요한 Tiny-X, 카페 등을 지원하기 위해 추가적으로 필요한 함수들도 구현되었다. 구현된 C표준 라이브러리는 EL/IX 응용프로그램 인터페이스 단계를 적용하지 않은 C표준 라이브러리보다 라이브러리 크기를 30% 정도 줄일 수 있었다. As the products of internet appliance, such as digital TV, internet set-top box, and internet phone, are continually produced, the market of real time operating system which controls those products is being highly increased. ETRI developed the extensible real time operating system, Qplus-P, which can be used from PDA to internet set-top box and home server. This paper describes the design and implementation of C standard library for real-time operating system Qplus-P. The Qplus-P C standard library follows EL/IX API level, which is proposed to the real-time operating system international standard by the RedHat. And, the C standard library functions, which are needed to support the Tiny-X and Kaffe, are also implemented. The implemented C standard library can reduce the size of library about 30% compare to the C library that does not follow EL/IX API level.