Green

1
Greens Functions and Matlabs cond function

• Wienand Drenth
• 11 December 2001

2
Overview

• What are Greens functions
• Example
• Implementation in MatLab
• Improvements to the design
• Future and NumLab

3
What are Greens functions
4
Example

• Instead of looking at globally defined continuous
  Greens functions, we aim at constructing locally
  defined discrete Greens functions.
• global
  local

5
Implementation in Matlab(1D, no details, only
features)

• Standard Matlab routines
• Assembly of stiffness matrix for applying Greens
  functions to
• Construction of Greens functions requires
  solution of small linear system

6
Improvements to the design

• Use sparse matrix instead of default fullGain
  in speed, but computation of condition number (by
  condest) is now an estimate
• Use routine condest for condition number instead
  of condGlobal behaviour of condition number
  remains the same

This is shown next
7
Comparison of computational times
8
Comparison of condition numbers
9
Future

• Investigation of 2 dimensional Greens functions
• Making the Matlab routines work within the NumLab
  environment