Evolution of Synthetic RTL Benchmark Circuits with Predefined Testability

1. Evolution of Synthetic RTL Benchmark Circuits with Predefined Testability Tomas Pecenka, Lukas Sekanina, Zdenek Kotasek Brno University of Technology, Faculty of Information Technology Božetěchova 2, 612 66 Brno kotasek@fit.vutbr.cz July 14, 2008 Humies 2008, Atlanta

2. Our entry • a set of benchmark digital circuits designed using an EA • These benchmark circuits • are intended for validation of CAD tools used in the area of digital circuits testing, • have a predefined structure and level of testability, • are the most complex benchmark circuits with an optional level of testability. • Publication: • Pecenka, T., Sekanina, L., Kotasek, Z.: Evolution of Synthetic RTL Benchmark Circuits with Predefined Testability. ACM Transactions on Design Automation of Electronic Systems (TODAES). Vol 13, No 3, 2008, 21 pages

3. Overview A circuit under design CAD tools for optimization of: area, timing, power consumption, … CAD tool for testability analysis Is the tool correct? The tool is validated using a set of benchmark circuits. The benchmarks should reveal weak points of used testability analysis (TA) algorithms. Circuit modification in order to improve the testability level of testability

4. Existing Benchmark Circuits • Real-world circuits • ISCAS85, ISCAS89, ITC99, ITC02 • max. 231,320 gates and 6,642 FFs • Synthetic sets • mainly composed of above-mentioned circuits • see references in TODAES paper • Main problem: • The benchmark sets used till now do not provide circuits with various levels of testability/complexity, which is important for consistent validation of testability analysis methods. • Our benchmarks – the starting testability parameters are known => it can be derived how the particular methodology improved testability and what is the size of the additional hardware.

5. Proposed benchmark circuits • EA is used to design benchmark circuits according to user specification • Input: type of components, the number of I/O, testability requirements, etc. • Output: RTL circuit with required complexity and testability • Benchmark set: • 24 circuits: from 2k gates to 1,2 M gates (after synthesis), four levels of testability 0%, 33%, 66%, 100% • 11 circuits: 108k gates, 11 levels of testability • In our methodology, evolutionary circuit design at the functional level is used (thousands of components in a circuit) • In the fitness function, the testability is calculated (quadratic time complexity). • Testability of evolved circuits is validated using a commercial CAD tool.

6. What we claim • D: The proposed method was accepted as a new solution for design of synthetic benchmark circuits by one of prominent journals (ACM TODAES) in the field of design and test of digital circuits. Proposed set of benchmarks was accepted independently of the fact that it was mechanically created. • G: Engineers have proposed various benchmark circuits in the area of digital circuits testing for many years. The main problem in their design is the need for simultaneous high complexity and controlled testability. Hence, the problem is seen as of indisputable difficulty in its field. The proposed method is able to provide the most complex circuits with a known level of testability.

7. Why we should win Humies 2008 (1) • A new concept was proposed for validation of testability analysis methods. • Instead of the use of “somehow” created benchmark sets, we can generate a well-targeted set of benchmark circuits which can systematically validate crucial features of TA methods. • optional complexity of benchmark circuits • optional testability of benchmark circuits • Important: We did not improve an existing solution only, we proposed a completely new concept.

8. Why we should win Humies 2008 (2) • The result was accepted as an innovation outside the EA community, independently of the fact that it was created by EA. • In the field of digital circuits testing, an extremely high competition can be observed (more than 50 years of development). • Many well-performing approaches have been proposed for this particular problem. • The community is really conservative and pragmatic with respect to completely new approaches and methodologies. • Have you attended a hardware-oriented conference? Many peopledo wear a tie there. Why? • Important: We have not presented our solution only to the EA community! • Pecenka, T., Sekanina, L., Kotasek, Z.: Evolution of Synthetic RTL Benchmark Circuits with Predefined Testability. ACM Transactions on Design Automation of Electronic Systems. Vol 13, No 3, 2008, 21 pages

9. Why we should win Humies 2008 (3) • The result strongly benefits from the use of the evolutionary approach. • As benchmark circuits are designed by means of the EA, they can contain constructions which do not usually appear in the circuits designed by classical design techniques. • Thus, the use of evolved benchmark circuits in the process of evaluating new TA tools can reveal problems that remain hidden when conventional benchmark circuits are used. • A story with one of commercial ATPG tools… • Important: We have really exploited the power of evolutionary design!

10. Why we should win Humies 2008 (4) • We evolved the largest objects (i.e. circuits containing more than 1.2M gates after synthesis) that have probably been created by an EA ever. • A promising application area was identified for evolvable hardware: Instead of function, structural properties of circuits can be sought by an EA! • Important:We have an interesting contribution into the evolvable hardware field.

11. Why we should win Humies 2008 (5) • In what ways does this paper advance the field? …the issue of making available benchmark circuits with the complexity compatible to state-of-the-art digital designs is relevant… To my knowledge, an original contribution to the area of the automated design of benchmarkcircuits for evaluation of Design-For-Testability methods. Anonymous reviewer

12. Thank you for your attention!