4,506 research outputs found
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
The GNAT method for nonlinear model reduction: effective implementation and application to computational fluid dynamics and turbulent flows
The Gauss--Newton with approximated tensors (GNAT) method is a nonlinear
model reduction method that operates on fully discretized computational models.
It achieves dimension reduction by a Petrov--Galerkin projection associated
with residual minimization; it delivers computational efficency by a
hyper-reduction procedure based on the `gappy POD' technique. Originally
presented in Ref. [1], where it was applied to implicit nonlinear
structural-dynamics models, this method is further developed here and applied
to the solution of a benchmark turbulent viscous flow problem. To begin, this
paper develops global state-space error bounds that justify the method's design
and highlight its advantages in terms of minimizing components of these error
bounds. Next, the paper introduces a `sample mesh' concept that enables a
distributed, computationally efficient implementation of the GNAT method in
finite-volume-based computational-fluid-dynamics (CFD) codes. The suitability
of GNAT for parameterized problems is highlighted with the solution of an
academic problem featuring moving discontinuities. Finally, the capability of
this method to reduce by orders of magnitude the core-hours required for
large-scale CFD computations, while preserving accuracy, is demonstrated with
the simulation of turbulent flow over the Ahmed body. For an instance of this
benchmark problem with over 17 million degrees of freedom, GNAT outperforms
several other nonlinear model-reduction methods, reduces the required
computational resources by more than two orders of magnitude, and delivers a
solution that differs by less than 1% from its high-dimensional counterpart
- …