Research in Dependable Computing


Behrooz Parhami: 2007/06/19  ||  E-mail:  ||  Problems:

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On June 19, 2007, Professor Parhami's UCSB ECE website moved to a new location. For an up-to-date version of this page, visit it at the new address:

In the following descriptions, selected items from B. Parhami’s list of publications are provided in brackets. 

Defining the Field

Dependability concerns are integral parts of engineering design. Aspects and/or measures of dependability for computer systems include reliability, availability, performability (sustained computational capability), safety, security, testability, and maintainability. Ideally, we would like our computer systems to be perfect, always yielding timely and correct (or at least safe) results. However, just as bridges collapse and airplanes crash occasionally, so too computer hardware and software cannot be made totally immune to undesirable or unpredictable behavior. Despite great strides in component reliability and programming methodology, the exponentially increasing complexity of integrated circuits and software products makes the design of perfect computer systems nearly impossible. The field of dependable computing [96] is concerned with studying the causes of imperfection in computer system (impairments to dependability), tolerance methods for ensuring correct, safe, or timely operation despite such impairments, and tools for evaluating the quality of proposed or implemented solutions.

Areas of Work

Methods for ensuring the uninterrupted and reliable functioning of digital computers in the presence of component faults and subsystem malfunctions are increasingly in demand as such systems expand in hardware and software complexity, perform a wider spectrum of critical functions, interact with a growing number of minimally trained users, and are expected to endure harsh or hostile operating environments. Thus, redundancy techniques, that were once limited to high-profile space and military projects, are becoming commonplace in run-of-the-mill computer systems. Unlike much work in the area of dependable computing, Professor Parhami’s focus is not solely on hardware reliability or software certification. Rather, he views result correctness as the central theme. His work thus combines elements of hardware redundancy, architectural flexibility, and algorithm robustness to achieve result correctness and graceful performance degradation. Because system reconfiguration and elimination of single points of failure invariably involve the use of multiple processors, Professor Parhami’s projects in dependable computing are intimately related to his research on parallel processing.

Current Threads

  • Dependable and fault-tolerant computer arithmetic [200], [201], [204]

  • Robust algorithms and architectures [152], [166], [192]

  • Extended-fault diameter of interconnection networks [183]

  • Methodology and unifying concepts [96], [133], [150], [199]

  • Testing and fault tolerance for processor arrays [88], [122], [140]

  • Voting schemes and data fusion [75], [94], [101], [118], [138], [223]


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Dr. Behrooz Parhami, Professor

                     Office phone: +1 805 893 3211
E-mail:                 Messages: +1 805 893 3716
Dept. Electrical & Computer Eng.                  Dept. fax: +1 805 893 3262
Univ. of California, Santa Barbara                Office: Room 5155 Eng. I
Santa Barbara, CA 93106-9560 USA                      Deliveries: Room 4155 Eng. I