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EE 616 Computer Aided Analysis of Electronic Networks Lecture 4. Instructor: Dr. J. A. Starzyk, Professor School of EECS Ohio University Athens, OH, 45701. 09/16/2005. Note: some materials in this lecture are from the notes of UC-berkeley. Review and Outline.
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EE 616 Computer Aided Analysis of Electronic NetworksLecture 4 Instructor: Dr. J. A. Starzyk, Professor School of EECS Ohio University Athens, OH, 45701 09/16/2005 Note: some materials in this lecture are from the notes of UC-berkeley
Review and Outline • Review of the previous lecture • * Network Equations and Their Solution • -- Gaussian elimination • -- LU decomposition (Doolittle and Crout algorithm) • -- Pivoting • -- Detecting ILL Conditioning • Outline of this lecture • * Rounding, Pivoting and Network scaling • * Sparse matrix • -- Data Structure • -- Markowitz product • -- Graph Approach
Sparse Matrices – Resistor Line Tridiagonal Case m
Sparse Matrices – Fill-in – Example 1 Nodal Matrix 0 Symmetric Diagonally Dominant
X X Sparse Matrices – Fill-in – Example 1 Matrix Non zero structure Matrix after one LU step X X X X X= Non zero
X X X X X Sparse Matrices – Fill-in – Example 2 Fill-ins Propagate X X X X X Fill-ins from Step 1 result in Fill-ins in step 2
Fill-ins 0 No Fill-ins 0 Sparse Matrices – Fill-in & Reordering Node Reordering Can Reduce Fill-in - Preserves Properties (Symmetry, Diagonal Dominance) - Equivalent to swapping rows and columns
Fill-in Estimate = (Non zeros in unfactored part of Row -1) (Non zeros in unfactored part of Col -1) Markowitz product Sparse Matrices – Fill-in & Reordering Where can fill-in occur ? Already Factored Possible Fill-in Locations Multipliers
Sparse Matrices – Data Structure • Several ways of storing a sparse matrix in a compact form • Trade-off • Storage amount • Cost of data accessing and update procedures • Efficient data structure: linked list
Sparse Matrices – Graph Approach Structurally Symmetric Matrices and Graphs
Sparse Matrices – Graph Approach Discuss example 2.8.1 (Page 73 ~ 74)