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Model Order Reduction of Model Order Reduction of Parameterized - - PowerPoint PPT Presentation

Model Order Reduction of Model Order Reduction of Parameterized Interconnect Networks Parameterized Interconnect Networks via a Two- -Directional Directional Arnoldi Arnoldi Process Process via a Two Yung-Ta Li joint work with Zhaojun


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Model Order Reduction of Model Order Reduction of Parameterized Interconnect Networks Parameterized Interconnect Networks via a Two via a Two-

  • Directional

Directional Arnoldi Arnoldi Process Process

Zhaojun Bai, Yangfeng Su, Xuan Zeng Yung-Ta Li

joint work with

RANMEP, Jan 5, 2008

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Problem statement Problem statement

Parameterized linear interconnect networks where Problem: find a reduced-order system where

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Application: Application: variational variational RLC circuit RLC circuit

Image source: OIIC

Complex Structure of Interconnects

spacing parameters

  • L. Daniel et al., IEEE TCAD 2004
  • J. Philips, ICCAD 2005

MNA (Modified Nodal Analysis)

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Application: Application: micromachined micromachined disk resonator disk resonator

Disk resonator PML region Silicon wafer Electrode

Cutaway schematic (left) and SEM picture (right) of a micromachined disk resonator. Through modulated electrostatic attraction between a disk and a surrounding ring of electrodes, the disk is driven into mechanical resonance. Because the disk is anchored to a silicon wafer, energy leaks from the disk to the substrate, where radiates away as elastic waves. To study this energy loss, David Bindel has constructed finite element models in which the substrate is modeled by a perfectly matched absorbing layer. Resonance poles are approximated by eigenvalues of a large, sparse complex-symmetric matrix pencil. For more details, see D. S. Bindel and S. Govindjee, "Anchor Loss Simulation in Resonators," International Journal for Numerical Methods in Engineering, vol 64, issue 6. Resonator micrograph courtesy of Emmanuel Quévy.

thickness

thickness

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Outline Outline

1. Transfer function and multiparameter moments 2. MOR via subspace projection

  • projection subspace and moment-matching

3. Projection matrix computation

  • “2D’’ Krylov subspace and Arnoldi process

4. Numerical examples

  • affine model of one geometric parameter
  • affine model of multiple geometric parameters
  • polynomial type model

5. Concluding remarks

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Transfer function

State space model:

One geometric parameter for clarity of presentation

Transfer function: : where for the frequency and

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Multiparameter Multiparameter moments and 2D recursion moments and 2D recursion

Power series expansion: Multiparameter moments: Moment generating vectors:

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Outline Outline

1. Transfer function and multiparameter moments 2. MOR via subspace projection

  • projection subspace and moment matching

3. Projection matrix computation

  • “2D’’ Krylov subspace and Arnoldi process

4. Numerical examples

  • affine model of one geometric parameter
  • affine model of multiple geometric parameters
  • polynomial type model

5. Concluding remarks

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MOR via subspace projection MOR via subspace projection

  • A proper projection subspace:
  • Orthogonal projection:
  • System matrices of the reduced-order system:
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MOR via subspace projection MOR via subspace projection

Goals: 1. 1. Keep the affined form in the state space equations Keep the affined form in the state space equations 2. 2. Preserve the stability and the passivity Preserve the stability and the passivity 3. 3. Maximize the number of matched moments Maximize the number of matched moments Goal 1 is guaranteed via orthogonal projection Goal 1 is guaranteed via orthogonal projection The number of matched moments is The number of matched moments is decided by the projection subspace decided by the projection subspace Goal 2 can be achieved if the original system complies Goal 2 can be achieved if the original system complies with a certain passive form with a certain passive form

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Projection subspace and moment Projection subspace and moment-

  • matching

matching

Projection subspace:

for (1) (2)

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Outline Outline

1. Transfer function and multiparameter moments 2. MOR via subspace projection

  • projection subspace and moment matching

3. Projection matrix computation

  • “2D’’ Krylov subspace and Arnoldi process

4. Numerical examples

  • affine model of one geometric parameter
  • affine model of multiple geometric parameters
  • polynomial type model

5. Concluding remarks

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Krylov Krylov subspace subspace

(1,i)th Krylov subspace: Use Arnoldi process to compute an orthonormal basis

] 1 [ ] 1 [

r

] 1 [ ] 2 [

r

] 1 [ ] 3 [

r

] 1 [ ] 4 [

r

] 1 [ ] 5 [

r

] 1 [ ] 6 [

r

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Krylov Krylov subspace subspace

(2,i)th Krylov subspace: : How to efficiently compute an orthonormal basis ?

] 2 [ ] 1 [

r

] 2 [ ] 2 [

r

] 2 [ ] 3 [

r

] 2 [ ] 4 [

r

] 2 [ ] 5 [

r

] 2 [ ] 6 [

r

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Efficiently compute Efficiently compute

] 2 [ ] 1 [

r

] 2 [ ] 2 [

r

] 2 [ ] 3 [

r

] 2 [ ] 4 [

r

] 2 [ ] 5 [

r

] 2 [ ] 6 [

r

Computed by 2D Arnoldi process

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Projection subspace Projection subspace 2D 2D Krylov Krylov subspace subspace

Define We have the linear recurrence where

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2D 2D Krylov Krylov subspace and 2D subspace and 2D Arnoldi Arnoldi decomposition decomposition

  • two-directional Arnoldi decomposition:

where

  • two properties:

Computed by 2D Arnoldi process vectors in the projection subspace be used to construct projection matrix

  • (j,i)th Krylov subspace:
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Generate V by 2D Generate V by 2D Arnoldi Arnoldi process process

Use V to construct reduced-order models by orthogonal projection PIMTAP (Parameterized Interconnect Macromodeling via a Two-directional Arnoldi Process)

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Outline Outline

1. Transfer function and multiparameter moments 2. MOR via subspace projection

  • projection subspace and moment-matching

3. Projection matrix computation

  • “2D’’ Krylov subspace and Arnoldi process

4. Numerical examples

  • affine model of one geometric parameter
  • affine model of multiple geometric parameters
  • polynomial type model

5. Concluding remarks

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RLC circuit with one parameter

RLC network: 8-bit bus with 2 shield lines variations on and

  • Structure-preserving MOR method : SPRIM [Freund, ICCAD 2004]
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RLC circuit : Relative error : Relative error

Compare PIMTAP and CORE [X Li et al., ICCAD 2005]

1 2 3 4 5 6 7 8 9 10 10

−16

10

−14

10

−12

10

−10

10

−8

10

−6

10

−4

10

−2

10 Frequency (GHz) Relative error: | h − h

^ | / | h |

CORE (p,q)=(40,1) CORE (p,q)=(80,1) PIMTAP (p,q)=(40,1)

CORE (p,q)=(40,1) CORE (p,q)=(80,1) PIMTAP (p,q)=(40,1)

  • rder of the ROM=76
  • rder of ROM=81
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RLC circuit : Numerical stability : Numerical stability

1 2 3 4 5 6 7 8 9 10 5 6 7 8 9 10 11 Frequency (GHz) |h(s)|

  • riginal

CORE (p,q)=(80,2) PIMTAP (p,q)=(40,2)

CORE (p,q)=(80,2) PIMTAP (p,q)=(40,2)

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2 4 6 8 10 10

−16

10

−14

10

−12

10

−10

10

−8

10

−6

10

−4

10

−2

Frequency (GHz) Relative error: abs( Horiginal − Hreduced )/ abs( Horiginal ) bus8b: λ = 0.06 PIMTAP (p,q)=(40,1) PIMTAP (p,q)=(40,2) PIMTAP (p,q)=(40,3) PIMTAP (p,q)=(40,4)

RLC circuit : PIMTAP for q=1,2,3,4 : PIMTAP for q=1,2,3,4

4

10−

2

10−

q=1,2 q=3,4

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Parametric thermal model Parametric thermal model [

[Rudnyi Rudnyi et al. 2005] et al. 2005]

Thermal model with parameters and Power series expansion of the transfer function on satisfies the recursion:

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Parametric thermal model Parametric thermal model

Stack the vectors via the following ordering:

  • (0,0,0)

(1,0,0) (0,1,0) (0,0,1) (2,0,0) (1,1,0) (1,0,1)(0,2,0)(0,1,1)(0,0,2) (0,0,0) (1,0,0) (0,1,0) (0,0,1) (2,0,0) …… (0,0,2)

The sequence :

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Polynomial type model Polynomial type model

State space model: Transfer function: Moment generating vectors:

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Projection subspace Projection subspace 2D 2D Krylov Krylov subspace subspace

Define We have the linear recurrence where

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Outline Outline

1. Transfer function and multiparameter moments 2. MOR via subspace projection

  • projection subspace and moment matching

3. Projection matrix computation

  • “2D’’ Krylov subspace and Arnoldi process

4. Numerical examples

  • affine model of one geometric parameter
  • affine model of multiple geometric parameters
  • polynomial type model

5. Concluding remarks

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Concluding remarks: Concluding remarks:

1.

PIMTAP is a moment matching based approach

2.

PIMTAP is designed for systems with a low- dimensional parameter space

3.

Systems with a high-dimensional parameter space are dealt by parameter reduction and PMOR

4.

A rigorous mathematical definition of projection subspaces is given for the design of Pad’e-like approximation of the transfer function

5.

The orthonormal basis of the projection subspace is computed adaptively via a novel 2D Arnoldi process

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Current projects: Current projects: Oblique projection

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Oblique projection

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References References

1.

Y.T. Li, Z. Bai, Y. Su, and X. Zeng, “Parameterized Model Order Reduction via a Two-Directional Arnoldi Process,’’ ICCAD 2007, pp. 868-873.

2.

Y.T. Li, Z. Bai, Y. Su, and X. Zeng, “Model Order Reduction of Parameterized Interconnect Networks via a Two-Directional Arnoldi Process,’’ IEEE TCAD, in revision.

3.

Y.T Li, Z. Bai, and Y. Su, “A Two-Directional Arnoldi Process and Applications,’’ Journal of Computational and Applied Mathematics, in revision.

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Thank you !