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Circuit Simulation via Matrix Exponential Operators CK Cheng UC San Diego 1
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Outline General Matrix Exponential Krylov Space and Arnoldi Orthogonalization Matrix Exponential Method – Krylov Subspace Approximation – Invert Krylov Subspace Approximation – Rational Krylov Subspace Approximation 2
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General Matrix Exponential 3
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Krylov Space and Arnoldi Orthonormalization Input A and v 1 =x 0 /|x 0 | Output AV=VH+h m+1 v m+1 e m T For i=1, …, m T i+1 =Av i For j=1, …, I – h ji = – T i+1 =T i+1 -h ji v j End For h i+1,i =|T i+1 | v i+1 =1/h i+1 T i+1 End For 4
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Standard Krylov Space Generate: AV=VH+h m+1 v m+1 e m T Thus, we have e Ah v 1 ≈ Ve Hh e 1 Residual r=Cdx/dt-Gx=-h m+1 Cv m+1 e m T e Hh e 1 Derivation: Cdx/dt-Gx=CVHe Hh e 1 -GVe Hh e 1 =(CVH-GV)e Hh e 1 = C(VH-C -1 GV)e Hh e 1 =C(VH-VH-h m+1 v m+1 e m T )e Hh e 1 =-h m+1 Cv m+1 e m T e Hh e 1 5
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Standard Mexp Error trend 6 sweep m and h
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Invert Krylov Space Generate: A -1 V=VH+h m+1 v m+1 e m T Let H=H -1, we have e Ah v 1 ≈ Ve Hh e 1 Residual r=Cdx/dt-Gx=h m+1 Gv m+1 e m T He Hh e 1 Derivation: Cdx/dt-Gx=CVHe Hh e 1 -GVe Hh e 1 =(CVH-GV)e Hh e 1 = G(G -1 CVH-V)e Hh e 1 =G(A -1 VH-V)e Hh e 1 =h m+1 Gv m+1 e m T He Hh e 1 7
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large step size with less dimension Invert Matrix Exponential 8 sweep m and h
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Rational Krylov Space Generate: (1-rA) -1 V=VH+h m+1 v m+1 e m T Let H=1/r (I-H -1 ) we have e Ah v 1 ≈ Ve Hh e 1 Residual r=Cdx/dt-Gx=-h m+1 (C/r-G)v m+1 e m T H -1 e Hh e 1 Derivation: Cdx/dt-Gx=CVHe Hh e 1 -GVe Hh e 1 =(CVH-GV)e Hh e 1 = (1/r CV(I-H -1 )-GV)e Hh e 1 =(1/rCV(H-1)-GVH)H -1 e Hh e 1 =((1/rC-G)VH-1/rCV)H -1 e Hh e 1 =-h m+1 (C/r-G)v m+1 e m T H -1 e Hh e 1 9
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large step size with less dimension Rational Matrix Exponential 10 fix , sweep m and h
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Different 11 needs large m
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Different 12
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Spectral Transformation – = 10f Small RC mesh, 100 by 100 Different h for Krylov subspace Different for rational Krylov subspace 13
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Spectral Transformation– = 1p Small RC mesh, 100 by 100 Different h for Krylov subspace Different for rational Krylov subspace 14
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Spectral Transformation– = 100p Small RC mesh, 100 by 100 Different h for Krylov subspace Different for rational Krylov subspace 15
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Sweep for Large Range 16
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Sweep for Large Range 17
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Difference Between Inverted and Rational 18
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Fixed = 1p, sweep time step h 19
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Fixed = 1n, sweep time step h 20
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Fixed = 1u, sweep time step h 21
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Fixed = 1m, sweep time step h 22
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Fixed = 1, sweep time step h 23
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Fixed = 1k, sweep time step h 24
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Fixed = 1M, sweep time step h 25
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Krylov Space Residual Generate: AV=VH+h m+1 v m+1 e m T Thus, we have e Ah v 1 ≈ Ve Hh e 1 Residual r=Cdx/dt-Gx=-h m+1 Cv m+1 e m T e Hh e 1 Derivation: 1. Set Y=[e 1 He 1 H 2 e 1 … H m-1 e 1 ] 2. We have YC=HY where C= z m +c m-1 z m-1 +…+c 1 z+c 0 =0 has roots 1, 2,… m 26 0-c 0 10-c 1 10-c 2 ……… 10-c m-2 1-c m-1
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Krylov Space Residual 27 1 1. 1 m-1 1 2. 2 m-1........... 1 m. m m-1
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Invert Krylov Space Residual 28
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