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Statistically Sound Verification and Optimization of Black-Box Systems
This thesis discusses two important problems for the design of practical systems under stochastic parameter variations: verification and optimization. Verification is concerned with the safety of a system, i.e., whether a system satisfies its specifications. If not, optimization is applied to tune the design parameters in the system so that the new design is safe. This thesis treats systems as black-boxes, assuming that the systems can be simulated efficiently but without detailed knowledge of the internal workings. It presents a series of simulation-based techniques to solve the problems of design verification and optimization. A notion called statistical soundness is introduced in this thesis, which guarantees that the outcome of the proposed techniques are “statistically certified” in the sense that the probability of drawing a wrong conclusion is bounded. For the problem of verification, this thesis develops a statistically sound model inference (SSMI) approach. SSMI constructs statistically sound models to explain the relationship between the stochastic parameters and the responses of a system. To improve the scalability of SSMI, a sparse approximation algorithm is also introduced. For the problem of optimization, this thesis presents a statistically sound optimization technique, SSMI-opt. SSMI-opt aims to find values of the design parameters for which the system satisfies the specifications. The proposed techniques can be applied to many interesting areas, including analog/mixd-signal circuits, embedded systems, biological systems, and medical devices. This thesis demonstrates the utility of this methodology on several interesting benchmark examples
Modeling and Analysis of Large-Scale On-Chip Interconnects
As IC technologies scale to the nanometer regime, efficient and accurate modeling
and analysis of VLSI systems with billions of transistors and interconnects becomes
increasingly critical and difficult. VLSI systems impacted by the increasingly high
dimensional process-voltage-temperature (PVT) variations demand much more modeling
and analysis efforts than ever before, while the analysis of large scale on-chip
interconnects that requires solving tens of millions of unknowns imposes great challenges
in computer aided design areas. This dissertation presents new methodologies
for addressing the above two important challenging issues for large scale on-chip interconnect
modeling and analysis:
In the past, the standard statistical circuit modeling techniques usually employ
principal component analysis (PCA) and its variants to reduce the parameter
dimensionality. Although widely adopted, these techniques can be very
limited since parameter dimension reduction is achieved by merely considering
the statistical distributions of the controlling parameters but neglecting
the important correspondence between these parameters and the circuit performances
(responses) under modeling. This dissertation presents a variety of
performance-oriented parameter dimension reduction methods that can lead to
more than one order of magnitude parameter reduction for a variety of VLSI
circuit modeling and analysis problems.
The sheer size of present day power/ground distribution networks makes their
analysis and verification tasks extremely runtime and memory inefficient, and
at the same time, limits the extent to which these networks can be optimized.
Given today?s commodity graphics processing units (GPUs) that can deliver
more than 500 GFlops (Flops: floating point operations per second). computing
power and 100GB/s memory bandwidth, which are more than 10X greater
than offered by modern day general-purpose quad-core microprocessors, it is
very desirable to convert the impressive GPU computing power to usable design
automation tools for VLSI verification. In this dissertation, for the first time, we
show how to exploit recent massively parallel single-instruction multiple-thread
(SIMT) based graphics processing unit (GPU) platforms to tackle power grid
analysis with very promising performance. Our GPU based network analyzer
is capable of solving tens of millions of power grid nodes in just a few seconds.
Additionally, with the above GPU based simulation framework, more challenging
three-dimensional full-chip thermal analysis can be solved in a much more
efficient way than ever before