Dr. Mubashir Alam King Saud University
Outline LU Factorization (6.4) Solution by LU Factorization Compact Variants of Gaussian Elimination, (Doolittle’s Method ) (6.4.1) Stability in Solving Linear Systems (6.5.2)
LU Factorization
Gaussian Elimination based on LU Factorization
Step:1 Step:2 Solve for g Solve for x
Example: (Page 284)
Compact Variants of Gaussian Elimination Doolittle’s Method
Dolittle’s Method
Example: (Page:285)
Stability in Solving Linear Systems Rounding Errors in Gaussian Elimination lead to errors in computed solution of Ax=b
Examine the degree of sensitivity of the solution ‘x’ to these rounding errors. Direct and complete analysis is difficult. Effect on the solution ‘x’ is done by making a small change in the right side ‘b’ of the linear system Stability in Solving Linear Systems How to measure the sizes of vectors and matrices?
Different Definition of Vector Norm Define and Use only One
Will use only || x || as notation
Matrix ‘A’ is the square matrix of size ‘n x n’
Vector Norm
(Same vector norm which we define in previous slides)
Condition Number
Example: (Page 300)