Nikhil Saluja

University of Colorado, Denver, Colorado, United States

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Publications (6)0 Total impact

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    ABSTRACT: In a typical IC design flow, circuits are optimized using multilevel don't cares. The computed don't cares are discarded before Technology Mapping or Automatic Test Pattern Generation (ATPG). In this paper, we present two combinational ATPG algorithms for combinational designs. These algorithms utilize the multilevel don't cares that are computed for the design during technology independent logic optimization. They are based on Boolean Satisfiability (SAT), and utilize the single stuck-at fault model. Both algorithms make use of the Compatible Observability Don't Cares (CODCs) associated with nodes of the circuit, to speed up the ATPG process. For large circuits, both algorithms make use of approximate CODCs (ACODCs), which we can compute efficiently. Our first technique speeds up fault propagation by modifying the active clauses in the transitive fanout (TFO) of the fault site. In our second technique, we define new j-active variables for specific nodes in the transitive fanin (TFI) of the fault site. Using these j-active variables we write additional clauses to speed up fault justification. Experimental results demonstrate that the combination of these techniques (when using CODCs) results in an average reduction of 45% in ATPG runtimes. When ACODCs are used, a speed-up of about 30% is obtained in the ATPG run-times for large designs. We compare our method against a commercial structural ATPG tool as well. Our method is slower for small designs, but for large designs, we obtain a 31% average speedup over the commercial tool.
    ACM Trans. Design Autom. Electr. Syst. 01/2008; 13.
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    J. Valavi, N. Saluja, S.P. Khatri
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    ABSTRACT: Wavelength division multiplexing (WDM) effectively multiplies the bandwidth of an optic fiber by transmitting data over several different wavelengths on the same fiber. WDM is widely used to handle the ever-increasing demand for bandwidth in fiber optic telecommunication networks. Routing and wavelength assignment (RWA) is a critical problem to be addressed in WDM optical telecommunication networks. The goal of RWA is to maximize throughput by optimally and simultaneously assigning routes and wavelengths for a given pattern of routing or connection requests. In this paper, we present a novel technique to solve the static RWA problem using Boolean satisfiability (SAT). After formulating the RWA problem as a SAT instance, we utilize a very efficient SAT solver to find a solution. We report results for networks with and without wavelength translation capabilities in the nodes. In both cases we obtain an assignment in significantly less than one second (which is 3-4 orders of magnitude faster than existing approaches) for a set of benchmark problems. Our technique can handle arbitrary network topologies, and, due to its efficiency, can be extended to handle dynamic RWA instances, in which the network topology, link capacities and connection requests are time-varying.
    Communications, 2005. ICC 2005. 2005 IEEE International Conference on; 06/2005
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    Nikhil Saluja, Sunil P. Khatri
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    ABSTRACT: In this paper, we present two combinational ATPG algorithms for combinational designs. These algorithms utilize the multi-level don't cares that are computed for the design during technology independent logic optimization. They are based on Boolean satisfiability (SAT), and utilize the single stuck-at fault model. Both algorithms make use of the compatible observability don't cares (CODCs) associated with nodes of the circuit, to speed up the ATPG process. For large circuits, both algorithms make use of approximate CODCs (ACODCs), which we can compute efficiently. Our first technique speeds up fault propagation by modifying the active clauses in the transitive fanout (TFO) of the fault site. In our second technique, we define new j-active variables for specific nodes in the transitive fanin (TFI) of the fault site. Using these j-active variables we write additional clauses to speed up fault justification. Experimental results demonstrate that the combination of these techniques (when using CODCs) results in an average reduction of 45% in ATPG run-times. When ACODCs are used, a speed-up of about 30% is obtained in the ATPG run-times for large designs. We compared our method against a commercial structural ATPG tool as well. Our method was slower for small designs, but for large designs, we obtained a 31% average speedup over the commercial tool.
    Proceedings 2005 IEEE International Test Conference, ITC 2005, Austin, TX, USA, November 8-10, 2005; 01/2005
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    Kunal R Shenoy, Nikhil S Saluja, Sunil P Khatri
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    ABSTRACT: In this paper, we describe an iterative heuristic technique to improve the quality of results obtained during two-level logic minimization using ESPRESSO. Although ESPRESSO minimizes the number of cubes in the solution e#ectively, there are several problem instances where its results are worse than the Quine-McCluskey based exact minimization technique. Our technique is designed to improve the results of ESPRESSO while utilizing ESPRESSO's Unate Recursive Paradigm based optimization heuristics, on account of their simplicity and power. Our technique is based on performing a series of iterations of ESPRESSO, in each of which we extract a number of cubes and append them into a HYPER-COVER. For the given (and subsequent) iterations of ESPRESSO, these cubes are considered as don't care cubes. By e#ectively selecting the number of iterations performed by our heuristic, we can trade o# the improvement in solution quality against the run-time of our algorithm. We have implemented several variants of our iterative algorithm, and have compared their e#ectiveness. We show that with a small number of iterations, our technique is able to improve on the number of cubes in the solution, with an acceptable run-time overhead. The best variant is able to improve the ESPRESSO cube count by up to 18%, with an acceptable increase in run-time. In 58 examples where the ESPRESSO results can be potentially improved, one of the variants of our algorithm demonstrated better results than ESPRESSO for 27 cases.
    04/2004;
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    Nikhil Saluja, Sunil P. Khatri
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    ABSTRACT: Not Available
    Proceedings of the 41th Design Automation Conference, DAC 2004, San Diego, CA, USA, June 7-11, 2004; 01/2004
  • N. Saluja, S.P. Khatri
    Design Automation Conference, 2004. Proceedings. 41st; 01/2004