Page last updated on 2020 September 29

*Enrollment code:* 12963

*Prerequisite:* ECE 154 (computer architecture), or equivalent

*Class meetings:* MW 10:00-11:30, Phelps 1440 (YouTube lectures)

*Instructor:* Professor Behrooz Parhami

*Open office hours:* MW 10:00-11:00 AM, via Zoom

**Course announcements:** Listed in reverse chronological order

**Course calendar:** Lecture, homework, and exam schedules

**Homework assignments:** Four assignments, worth a total of 40%

**Exams:** None for fall 2020

**Research paper:** Report 50%; Poster 10%

**Research paper guidlines:** Brief guide to format and contents

**Poster presentation tips:** Brief guide to format and structure

**Policy on academic integrity:** Please read very carefully

**Grades:** Statistics for homework and exam grades

**References:** Textbook and other sources (Textbook's web page)

**Lecture slides:** Via the textbook's Web page

**Miscellaneous information:** Motivation, catalog entry, history

**2020/09/29:** Course update sent to students via GauchoSpace: Updated versions of the textbook Chapters 1-4 (Part I) and associated slides have been posted to the textbook's Web page. A forthcoming ACM webinar by Dr. Moshe Vardi, entitled "Lessons from COVID-19: Efficiency vs Resilience," is of great interest to this course (Registration). It will be offered on Wednesday, October 14, 9:00 AM PDT. Please watch it if you can, as a problem in our HW1 relates to this presentation. If you cannot watch the webinar, there are alternate sources that I will specify in the problem statements for HW1. Videos for Lectures 1 and 2 (week of September 5 to 9) will be posted by the end of this week.
**2020/09/25:** Introductory message sent to the 11 enrolled students via GauchoSpace: I hope your summer was fun and/or productive, despite the difficult circumstances arising from the coronavirus pandemic. As your instructor for this course, I will try to function more or less normally during fall and provide you with significant learning opportunities with a modified course format to accommodate on-line instruction.

During the fall 2020 quarter, you will need to consult two Web pages on a regular basis: This course page and the textbook page. I will use GauchoSpace only for announcements and not as the main communication medium for the course.

Course lectures will be asynchronous, using the flipped-classroom model. I will record the lectures, post them on YouTube, and provide you with the link for watching. The first hour of each class session (MW 10:00-11:00) will be devoted to a Zoom office hour. I will also be available for answering questions through e-mail. ECE 257A requirements and grading scheme are described near the top of this Web page.

I will send you links to the first couple of lectures soon. I will also inform you when I have updated the first four chapters of the textbook, so that you can download them from the textbook's Web page.

Looking forward to interacting with you during the fall quarter!
**2020/07/26:** Free conference attendance: The European Dependable Computing Conference will be held virtually from September 8 to 10, 2010. Intel and Fraunhofer IKS are covering all organizational expenses. Hence, participation is free of charge, but you need to pre-register. [Conference program] [Workshops]
**2020/06/11:** Welcome to the ECE 257A web page for fall 2020. The course will be research-based, with 60% of your grade determined by your research report and poster presentation and 40% based on homework. I plan to update the lecture slides and textbook chapters over the summer months and through the fall quarter, with each revised chapter becoming available before discussion in class.

Course lectures, homework assignments, and research paper deadlines have been scheduled as follows. This schedule will be strictly observed. In particular, no extension is possible for homework due dates. Please begin work on your assignments early. Each lecture corresponds to topics in 1-2 chapters of the instructor's forthcoming textbook on dependable computing. Chapter numbers are provided in parentheses, after day & date.

**Day & Date (book chapters) Lecture topic [Homework posted/due] {Special notes}**

M 10/05 (1) Background and motivation

W 10/07 (2) Dependability attributes

M 10/12 (3) Combinational modeling [HW1 posted, chs. 1-4]

W 10/14 (4) State-space modeling

M 10/19 (5, 7) Defect avoidance; Shielding and hardening {Research topics specified}

W 10/21 (6, 8) Defect circumvention; Yield enhancement [HW1 due]

M 10/26 (9, 11) Fault testing; Design for testability [HW2 posted, chs. 5-12]

W 10/28 (10, 12) Fault masking; Replication with voting {Research assignments finalized}

M 11/02 (13, 15) Error detection; Self-checking modules

W 11/04 (14, 16) Error correction; Redundant disk arrays [HW2 due]

M 11/09 Research-focus week: Getting started {Preliminary reference list due}

W 11/11 No lecture (Veterans' Day) [HW3 posted, chs. 13-20]

M 11/16 (17, 19) Malfunction diagnosis; Standby redundancy

W 11/18 (18, 20) Malfunction tolerance; Robust parallel processing

M 11/23 (21, 23) Degradation allowance; Resilient algorithms [HW3 due]

W 11/25 (22, 24) Degradation management; Software redundancy [HW4 posted, chs. 21-28]

M 11/30 (25, 27) Failure confinement; Agreement and adjudication {References and provisional abstract due}

W 12/02 (26, 28) Failure recovery; Fail-safe systems

M 12/07 Research-focus week: Finishing up [HW4 due]

W 12/09 Poster presentations {PDF of poster due} {Instructor and course evaluations}

W 12/16 {Full research paper PDF file due by midnight}

W 12/23 {Course grades due by midnight}

-Turn in your solutions as a PDF file attached to an e-mail sent by the due date/time.

-Because solutions will be handed out on the due date, no extension can be granted.

-Include your name, course name, and assignment number at the top of the first page.

-If homework is handwritten and scanned, make sure that the PDF is clean and legible.

-Although some cooperation is permitted, direct copying will have severe consequences.

** Homework 1: Dependability and its modeling** (chs. 1-4, due W 2020/10/21, 10:00 AM)

Do the following problems from the textbook: To be posted here no later than M 10/12

** Homework 2: Defects and faults** (chs. 5-12, due W 2020/11/04, 10:00 AM)

Do the following problems from the textbook: To be posted here no later than M 10/26

** Homework 3: Errors and malfunctions** (chs. 13-20, due M 2020/11/23, 10:00 AM)

Do the following problems from the textbook: To be posted here no later than W 11/11

** Homework 4: Degradations and failures** (chs. 21-28, due W 2020/12/07, 10:00 AM)

Do the following problems from the textbook: To be posted here no later than W 11/25

(This section does not apply to fall 2020)

The following sample exam problems are meant to indicate the types and levels of problems, rather than the coverage (which is outlined in the course calendar).

Students are responsible for all sections and topics in the textbook and class handouts that are not explicitly excluded in the study guide that follows each sample exam, even if the material was not covered in class lectures.

*Sample Midterm Exam (105 minutes)*

Problems 3.12, 4.4, 9.4, and 12.1 from the textbook.

*Midterm Exam Study Guide*

Study Chapters 1-12 and review the problems in homework assignments 1-2. The following textbook sections are excluded: 6.6, 7.6, 8.6, 9.4, 9.6, 11.6

*Sample Final Exam (120 minutes)*

Problems 15.5, 17.1, 21.2, and 27.3 from the textbook.

*Final Exam Study Guide*

Study Chapters 13-28 and review the problems in homework assignments 3-4. The following textbook sections are excluded: 13.6, 14.6

Each student will review a subfield of dependable computing or do original research on a selected and approved topic. A preliminary list of research topics is provided below (new topics, and new references for the current topics, may be added later). However, students should feel free to propose their own topics for approval. To propose a topic, send via e-mail a one-page narrative, including 2-3 key references, to the instructor.

A publishable report earns an "A" for the course, regardless of homework and midterm grades. See the course calendar for schedule and due dates and Research Paper Guidlines for formatting tips.

This year's suggested research topics for ECE 257A are built around the theme "Robustness of Interconnection networks." You can get started on each topic by taking a look at the following two common references, plus one topic-specific reference that is provided further down on this page. The two common references are:

[Parh10] Parhami, B., "Robustness Attributes of Interconnection Networks for Parallel Processing," Keynote Lecture at the First Int'l Supercomputing Conf., Guadalajara, Mexico, March 2010. {PPT and PDF slides are available from B. Parhami's Publications Web page; see publication [262].}

[Sall12] Salles, R. M. and D. A. Marion Jr., "Strategies and Metric for Resilience in Computer Networks," *Computer J.*, Vol. 55, No. 6, pp. 728-739, June 2012.

1. Effects of Missing Nodes on Network Diameter and Average Distance (Assigned to: TBD)

[Kris87] Krishnamoorthy, M.S. and B. Krishnamurthy, "Fault Diameter of Interconnection Networks," *Computers & Mathematics with Applications*, Vol. 13, Nos. 5/6, pp. 577-582, 1987.

2. Effects of Missing Links on Network Diameter and Average Distance (Assigned to: TBD)

[Kris87] Krishnamoorthy, M.S. and B. Krishnamurthy, "Fault Diameter of Interconnection Networks," *Computers & Mathematics with Applications*, Vol. 13, Nos. 5/6, pp. 577-582, 1987.

3. Synthesis of Interconnection Networks with Maximal Fault Tolerance (Assigned to: TBD)

[Chen09] W. Chen, W. J. Xiao, and B. Parhami, "Swapped (OTIS) Networks Built of Connected Basis Networks are Maximally Fault Tolerant," *IEEE Trans. Parallel and Distributed Systems*, Vol. 20, pp. 361-366, March 2009.

4. Adaptive Schemes for Point-to-Point Communication in Networks (Assigned to: TBD)

[Ngai91] Ngai, J. Y. and C. L. Seitz, "A Framework for Adaptive Routing in Multicomputer Networks," *Computer Architecture News*, Vol. 19, No. 1, pp. 6-14, March 1991.

5. Adaptive Schemes for Collective Communication in Networks (Assigned to: TBD)

[Pand95] Panda, D. K., "Issues in Designing Efficient and Practical Algorithms for Collective Communication on Wormhole-Routed Systems," *Proc. Int'l Conf. Parallel Processing Workshop on Challenges for Parallel Processing*, 1995, pp. 8-15.

6. Deadlocks in Adaptive Routing and How to Avoid or Detect Them (Assigned to: TBD)

[Dall93] Dally, W. J. and H. Aoki, "Deadlock-Free Adaptive Routing in Multicomputer Networks Using Virtual Channels," *IEEE Trans. Parallel and Distributed Systems*, Vol. 4, No. 4, pp. 466-475, April 1993.

7. Diagnosability of Regular Degree-*d* Interconnection Networks (Assigned to: TBD)

[Chan05] Chang, G.-Y., G. J. Chang, and G.-H. Chen, "Diagnosabilities of Regular Networks," *IEEE Trans. Parallel and Distributed Systems*, Vol. 16, No. 4, pp. 314-323, April 2005

8. Diagnosability of Hierarchical or Multilevel Interconnection Networks (Assigned to: TBD)

[Xu09] Xu, M., K. Thulasiraman, and X.-D. Hu, "Conditional Diagnosability of Matching Composition Networks Under the PMC Model," *IEEE Trans. Circuits and Systems II*, Vol. 56, No. 11, pp. 875-879, November 2009.

9. Synthesis of Interconnection Networks with Maximal Diagnosability (Assigned to: TBD)

[Chan05] Chang, G.-Y., G. J. Chang, and G.-H. Chen, "Diagnosabilities of Regular Networks," *IEEE Trans. Parallel and Distributed Systems*, Vol. 16, No. 4, pp. 314-323, April 2005

*Topics outside the main theme for the quarter*

a. Reasoning Under Uncertainly, with Applications to Dependable Computing (Assigned to: TBD)

[IJAR16] *Int'l J. Approximate Reasoning*, Vol. 71, pp. 1-62, December 2016 (Five review articles on 40 years of Dempster-Shafer Theory)

b. Probabilistic Analysis of Program Correctness Under Soft Errors (Assigned to: TBD)

[Carb16] Carbin, M., S. Misailovic, and M. C. Rinard, "Verifying Quantitative Reliability for Programs that Execute on Unreliable Hardware," *Communications of the ACM*, Vol. 59, No. 8, pp. 83-91, August 2016.

c. Effects of Temporal Resistance-State Variation on ReRAM Reliability (Proposed by: TBD)

[Ref 1] "Modeling Framework for Cross-Point Resistive Memory Design Emphasizing Reliability and Variability Issues"

d. Computation-Oriented Fault Tolerance Schemes for RRAM-Based Systems (Proposed by: TBD)

[Chen15] Chen, C.-Y., et al., "RRAM Defect Modeling and Failure Analysis Based on March Test and a Novel Squeeze-Search Scheme," *IEEE Trans. Computers*, Vol. 64, No. 1, pp. 180-190, January 2015.

Here are some guidelines for preparing your research poster. The idea of the poster is to present your research results and conclusions thus far, get oral feedback during the session from the instructor and your peers, and to provide the instructor with something to comment on before your final report is due. Please send a PDF copy of the poster via e-mail by midnight on the poster presentation day.

Posters prepared for conferences must be colorful and eye-catching, as they are typically competing with dozens of other posters for the attendees' attention. Here is an example of a conference poster. Such posters are often mounted on a colored cardboard base, even if the pages themselves are standard PowerPoint slides. In our case, you should aim for a "plain" poster (loose sheets, to be taped to the wall in our classroom) that conveys your message in a simple and direct way. Eight to 10 pages, each resembling a PowerPoint slide, would be an appropriate goal. You can organize the pages into 2 x 4 (2 columns, 4 rows), 2 x 5, or 3 x 3 array on the wall. The top two of these might contain the project title, your name, course name and number, and a very short (50-word) abstract. The final two can perhaps contain your conclusions and directions for further work (including work that does not appear in the poster, but will be included in your research report). The rest will contain brief description of ideas, with emphasis on diagrams, graphs, tables, and the like, rather than text which is very difficult to absorb for a visitor in a very limited time span.

*All grades listed are in percent, unless otherwise noted*.

HW1 grades (letter): Range = [L, H], Mean = 0.00, Median = M

HW2 grades (letter): Range = [L, H], Mean = 0.00, Median = M

HW3 grades (letter): Range = [L, H], Mean = 0.00, Median = M

HW4 grades (letter): Range = [L, H], Mean = 0.00, Median = M

Overall homework grades (out of 16): Range = [00.0, 00.0], Mean = 00.0, Median = 00.0

Research paper grades: Range = [00, 00], Mean = 00, Median = 00

Course grades (letter): Range = [L, H], Mean = 0.00, Median = M

** Required text:** B. Parhami,

Koren/Krishna,

Shooman,

Siewiorek/Swarz,

Johnson,

*Research resources:**Proc. IEEE/IFIP Int'l Conf. Dependable Systems and Networks* (DSN), formerly known as Fault-Tolerant Computing Symp. (FTCS), annual, since 1971.
*IEEE Trans. Dependable and Secure Computing*, published since 2004
*IEEE Trans. Reliability*, published since 1955
*IEEE Trans. Computers*, published since 1952

UCSB library's electronic journals, collections, and other resources

** Motivation:** Dependability concerns are integral parts of engineering design. Ideally, we would like our computer systems to be perfect, always yielding timely and correct results. However, just as bridges collapse and airplanes crash occasionally, so too computer hardware and software cannot be made totally immune to unpredictable behavior. Despite great strides in component reliability and programming methodology, the exponentially increasing complexity of integrated circuits and software systems makes the design of prefect computer systems nearly impossible. In this course, we study the causes of computer system failures (impairments to dependability), techniques for ensuring correct and timely computations despite such impairments, and tools for evaluating the quality of proposed or implemented solutions.

*Catalog entry:* 257A. Fault-Tolerant Computing. (4) PARHAMI.*Prerequisites: ECE 154. Lecture, 3 hours*. Basic concepts of dependable computing. Reliability of nonredundant and redundant systems. Dealing with circuit-level defects. Logic-level fault testing and tolerance. Error detection and correction. Diagnosis and reconfiguration for system-level malfunctions. Degradation management. Failure modeling and risk assessment.

** History:** Professor Parhami took over the teaching of ECE 257A in the fall quarter of 1998. Previously, the course had been taught primarily by Dr. John Kelly, who instituted the two-course sequence ECE 257A/B, the first covering general topics and the second (now discontinued) devoted to his research focus on software fault tolerance. Borrowing from his experience in teaching dependable computing at other universities and based on an extensive survey of the field that he published in 1994, Professor Parhami oriented the course toward an original multilevel view of impairments to computer system dependability and techniques for avoiding or tolerating them. The levels of this models, in increasing order of abstraction, are: defects, faults, errors, malfunctions, degradations, and failures. A textbook based on this multilevel model of dependable computing is in preparation.

Offering of ECE 257A in fall 2019

Offering of ECE 257A in fall 2018

Offering of ECE 257A in fall 2016 (PDF file)

Offering of ECE 257A in fall 2015 (PDF file)

Offering of ECE 257A in winter 2015 (PDF file)

Offering of ECE 257A in fall 2013 (PDF file)

Offering of ECE 257A in fall 2012 (PDF file)

Offering of ECE 257A in fall 2009 (PDF file)

Offering of ECE 257A in fall 2007 (PDF file)

Offerings of ECE 257A in 1998 and 2006 (PDF file)