Parallel Test Generation Research Articles

Analog Automatic Test Pattern Generation for Quasi-Static Structural Test

A new approach for structural, fault-oriented analog test generation methodology to test for the presence of manufacturing-related defects is proposed. The output of the test generator consists of optimized test stimuli, fault coverage and sampling instants that are sufficient to detect the failure modes in the circuit under test. The tests are generated and evaluated on a multistep ADC taking into account the potential fault masking effects of process spread on the faulty circuit responses. Similarly, the test generator results offer indication for the circuit partitioning within the framework of circuit performance, area and testability.

Parallel VLSI test in a shared-memory multiprocessor

This paper presents three parallel procedures implemented in a shared-memory multiprocessor to generate the patterns that allow the testing of digital circuits. The implementation of these procedures in a multiprocessor uses the system memory better than in a distributed-memory multicomputer, since it is not necessary to store the circuit structure in the local memory of each processor, besides other common structures. The parallel test generation procedures are based on a new sequential algorithm which mixes both the Boolean difference and digital spectral techniques. It is thus different from other methods proposed that deal with the parallelization of test generation algorithms that carry out an implicit enumeration of the input pattern space. The first procedure distributes the set of faults using a backtracking procedure starting from a primary output and allocating a similar number of lines to each processor. The second procedure distributes the set of faults among the processors taking into account the distance from each line to its nearest primary output; it then applies the algorithm to generate the test pattern with some modifications. The third procedure uses a circuit partitioning procedure which allows similar sized parts of the circuit to be assigned to each processor while communications between processors are minimized. The experimental results obtained when the procedures are applied to the usual benchmark circuits (the ISCAS set) show figures for speedup better than in a multicomputer, although fewer processors are used. Copyright © 2000 John Wiley & Sons, Ltd.

Test Generation for Mixed-Signal Devices Using Signal Flow Graphs

We describe a new reverse simulation approach to analog and mixed-signal circuit test generation that parallels digital test generation. We invert the analog circuit signal flow graph, reverse simulate it with good and bad machine outputs, and obtain test waveforms and component tolerances, given circuit output tolerances specified by the functional test needs of the designer. The inverted graph allows backtracing to justify analog outputs with analog input sinusoids. Mixed-signal circuits can be tested using this approach, and we present test generation results for two mixed-signal circuits and four analog circuits, one being a multiple-input, multiple-output circuit. This analog backtrace method can generate tests for second-order analog circuits and certain non-linear circuits. These cannot be handled by existing methods, which lack a fault model and a backtrace method. Our proposed method also defines the necessary tolerances on circuit structural components, in order to keep the output circuit signal within the envelope specified by the designer. This avoids the problem of overspecifying analog circuit component tolerances, and reduces cost. We prove that our parametric fault tests also detect all catastrophic faults. Unlike prior methods, ours is a structural, rather than functional, analog test generation method.

Annealing-based heuristics and genetic algorithms for circuit partitioning in parallel test generation

In this paper simulated annealing and genetic algorithms are applied to the graph partitioning problem. These techniques mimic processes in statistical mechanics and biology, respectively, and are the most popular meta-heuristics or general-purpose optimization strategies. A hybrid algorithm for circuit partitioning, which uses tabu search to improve the simulated annealing meta-heuristics, is also proposed and compared with pure tabu search and simulated annealing algorithms, and also with a genetic algorithm. The solutions obtained are compared and evaluated by including the hybrid partitioning algorithm in a parallel test generator which is used to determine the test patterns for the circuits of the frequently used ISCAS benchmark set.

An analysis of fault partitioned parallel test generation

Generation of test vectors for the VLSI devices used in contemporary digital systems is becoming much more difficult as these devices increase in size and complexity. Automatic Test Pattern Generation (ATPG) techniques are commonly used to generate these tests. Since ATPG is an NP complete problem with complexity exponential to circuit size, the application of parallel processing techniques to accelerate the process of generating test vectors is an active area of research. The simplest approach to parallelization of the test generation process is to simply divide the processing of the fault list across multiple processors, Each individual processor then performs the normal test generation process on its own portion of the fault list, typically without interaction with the other processors. The major drawback of this technique, called fault partitioning, is that the processors perform redundant work generating test vectors for faults covered by vectors generated on another processor. An earlier approach to reducing this redundant work involved transmitting generated test vectors among the processors and fault simulating them on each processor. This paper presents a comparison of the vector broadcasting approach with the simpler and more effective approach of fault broadcasting. In fault broadcasting, fault simulation is performed on the entire fault list on each processor. The resulting list of detected faults is then transmitted to all the other processors. The results show that this technique produces greater speedups and smaller test sets than the test vector broadcasting technique. Analytical models are developed which can be used to determine the cost of the various parts of the parallel ATPG algorithm. These models are validated using data from benchmark circuits.

Optimal granularity and scheme of parallel test generation in a distributed system

Client-Agent-Server model (CAS model) which can decrease the work load of the client by adding agent processors to the Client-Server model (CS model) is proposed and an approach to parallel test generation for logic circuits on the CAS model is presented. Two problems are considered: optimal granularity problem and optimal scheme problem. First, the problem of parallel test generation on the CAS model is formulated to analyze the effect of the granularity (grain size of target faults allocated to processors) in both cases of static and dynamic task allocation (optimal granularity problem). Then the relationship between the number of processors and the total processing time is analyzed (optimal scheme problem). From the analysis, it is shown that the CAS model can reduce the total processing time over the CS model and that there exists an optimal scheme (an optimal pair of numbers of agent processors and server processors) for the CAS model which minimizes the total processing time for a given number of processors. To corroborate the analysis, the proposed parallel test generation algorithm is implemented on a network of more than 100 workstations and experimental results for the ISCAS benchmark circuits are presented. It is shown that the experimental results are very close to the theoretical results which confirms the existence of optimal granularity and optimal scheme which minimizes the total processing time for the CAS model. >

Performance trade-offs in a parallel test generation/fault simulation environment

Heuristics are proposed to partition faults for parallel test generation with minimization of both the overall run time and test length as an objective. For efficient utilization of available processors, the work load has to be balanced at all times. Since it is very difficult to predict how difficult it will be to generate a test for a particular fault, the authors propose a load balancing method which uses static partitioning initially and then uses dynamic allocation of work for processors which become idle. A theoretical model is presented to predict the performance of the parallel test generation/fault simulation process. Experimental results based on an implementation of the Intel IPSC/2 hypercube multiprocessor using the ISCAS combinational benchmark circuits are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A parallel branch and bound algorithm for test generation

For circuits of VLSI complexity, test generation time can be prohibitive. Most of the time is consumed by hard-to-detect (HTD) faults, which might remain undetected even after a large number of backtracks. The problems inherent in a uniprocessor implementation of a test generation algorithm are identified, and a parallel test generation method which tries to achieve a high fault coverage for HTD faults in a reasonable amount of time is proposed. A dynamic search space allocation strategy which allocates disjoint search spaces to minimize the redundant work is proposed. The search space allocation strategy tries to utilize the partial solutions generated by other processors to increase the probability of searching in a solution area. The parallel test generation algorithm has been implemented on an Intel iPSC/2 hypercube. It is shown that parallel processing of HTD faults does indeed result in high fault coverage, which is otherwise not achievable by a uniprocessor algorithm. The parallel algorithm exhibits superlinear speedups in some cases due to search anomalies. >

Toward massively parallel automatic test generation

A new automatic test pattern generation (ATPG) methodology that has the potential to exploit fine-grain parallel computing and relaxation techniques is described. This approach is radically different from the conventional methods used to generate tests for circuits from their gate level description. The digital circuit is represented as a bidirectional network of neurons. The circuit function is coded in the firing thresholds of neurons and the weights of interconnection links. This neural network is suitably reconfigured for solving the ATPG problem. A fault is injected into the neural network and an energy function is constructed with global minima at test vectors. The authors simulated the neural network on a serial computer, and determined the global minima of the energy function using a directed search technique augmented by probabilistic relaxation. Preliminary results on combinational circuits confirm the feasibility of this technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Automatic test generation techniques for analog circuits and systems: A review

The purpose of this paper is both a review and an assessment of techniques presently available for automatic test generation for analog systems. After recalling the general problems of automatic testing (definitions, faults in analog systems, different types of tests, main operations, and diagnosis procedures), characterization and description modes of analog systems, and the main software ingredients of automatic test equipment, a categorization of known techniques along several criteria can be proposed. Then, several techniques, respectively, proceeding from approaches based on deterministic and probabilistic estimation, taxonomical and topological analyses can be detailed. Techniques specific to linear systems (several of them belonging to the above three categories) are dealt with in a separate section. The main features of the techniques that are described are summed up in five synoptic tables. As a conclusion, several research areas that need further investigation in view of a possible industrial implementation of automatic analog test generation techniques are identified. Two appendixes deal briefly with fault tolerance and fault simulation in analog systems. An extensive bibliography ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim</tex> 500 entries) is provided.