Improving Particle Methods Robert Krasny (Michigan) collaborators - - PowerPoint PPT Presentation

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Improving Particle Methods Robert Krasny (Michigan) collaborators - - PowerPoint PPT Presentation

March 12-16, 2018 ICERM Workshop on Fast Algorithms for Generating Static and Dynamically Changing Point Configurations Improving Particle Methods Robert Krasny (Michigan) collaborators Weihua Geng (Southern Methodist University) Peter


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SLIDE 1

March 12-16, 2018 ICERM Workshop on “Fast Algorithms for Generating Static and Dynamically Changing Point Configurations”

Improving Particle Methods

Robert Krasny (Michigan) collaborators

Weihua Geng (Southern Methodist University) Peter Bosler (Sandia National Laboratories) Ling Xu (Michigan)

support

NSF DMS-1418966 ONR N00014-14-1-0075 MICDE (Michigan Institute for Computational Discovery and Engineering)

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  • utline
  • 1. protein-solvent electrostatics
  • 2. incompressible fluid flow
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SLIDE 3
  • 1. protein-solvent electrostatics

atomic charges Van der Waals radius water molecules molecular surface dissolved salt ions

goal

φ(x) : electrostatic potential Esol : electrostatic solvation energy

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Poisson-Boltzmann implicit solvent model

yk Ω1, ✏1 Ω2, ✏2 Γ

Ω1 : protein domain : ✏1r2(x) =

Nc

X

k=1

qk(x yk) Ω2 : solvent domain : ✏2r2(x) ¯ 2(x) = 0 : PB equation Γ : molecular surface : 1 = 2 , ✏1 @1 @n = ✏2 @2 @n far-field boundary condition : lim

|x|→∞(x) = 0

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SLIDE 5

boundary integral formulation Juffer et al. (1991)

G0(x, y) = 1 4⇡|x − y| : Coulomb potential G(x, y) = e−|x−y| 4⇡|x − y| : screened Coulomb potential , 2 = ¯ 2/✏2

1 2

⇣ 1 + ✏2

✏1

⌘ (x) = Z

Γ

h K1(x, y)@n(y) + K2(x, y)(y) i dSy + S1(x)

1 2

⇣ 1 + ✏1

✏2

⌘ @n(x) = Z

Γ

h K3(x, y)@n(y) + K4(x, y)(y) i dSy + S2(x) K1 = G0 − G , K2 = ✏2 ✏1 @nyG − @nyG0 K4 = @2

nxny(G − G0) , K3 = @nxG0 − ✏1 ✏2@nxG

S1(x) = 1 ✏1

Nc

X

k=1

qkG0(x, yk) , S2(x) = 1 ✏1

Nc

X

k=1

qk@nxG0(x, yk)

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SLIDE 6

discretization

triangulation + centroid collocation xi : centroid , Ai : area , i = 1 : N

1 2

⇣ 1 + ✏2

✏1

⌘ φi =

N

X

j=1 j6=i

h K1(xi, xj)∂nφj + K2(xi, xj)φj i Aj + S1(xi)

1 2

⇣ 1 + ✏1

✏2

⌘ ∂nφi =

N

X

j=1 j6=i

h K3(xi, xj)∂nφj + K4(xi, xj)φj i Aj + S2(xi) ⇒ linear system : Ax = b

  • GMRES
  • matrix-vector product at each step
  • fast summation → treecode
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SLIDE 7

treecode : higher-order version of Barnes-Hut (1986)

φi =

N

X

j=1 j6=i

qjG(xi, xj) , i = 1, . . . , N : particle-particle , O(N 2) ≈ X

c p

X

k=0

ak(xi, xc)M k(c) : particle-cluster , O(N log N)

  • Cartesian coordinates
  • recurrence relations for ak(xi, xc) = 1

k!Dk yG(x, xc)

  • geometrically adaptive
  • low memory usage, good parallel efficiency

Li-Johnston-K (2009) JCP 228

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SLIDE 8

example : protein 1A63

RNA binding domain of E. coli rho factor 2069 atoms , triangulation by MSMS with N = 132196

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SLIDE 9

example : protein 1A63

compare 2 codes

TABI : N = 20K → 500K APBS : grid = 65 × 332 → 513 × 3212 , hmax = 1.63 ˚ A → 0.13 ˚ A

10 10

1

10

1

10

2

10

3

error in Esol (%) CPU time (s) 3% 6% TABI−PB TABI−P APBS−PB APBS−P 10 10

1

10

1

10

2

10

3

10

4

error in Esol (%) memory (MB) TABI−PB TABI−P APBS−PB APBS−P

CPU time / error memory / error

Geng-K (2013) JCP 247

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SLIDE 10

example : protein 1A63

TABI parallel performance , N = 132196 , error in Esol ≈ 1.3% Poisson-Boltzmann # processors run time (s) speedup parallel efficiency (%) 1 799.3 1.00 100.0 2 410.0 1.95 97.5 4 223.8 3.57 89.3 8 123.7 6.46 80.9 Poisson # processors run time (s) speedup parallel efficiency (%) 1 324.4 1.00 100.0 2 166.7 1.95 97.3 4 92.6 3.50 87.6 8 51.0 6.36 79.5

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SLIDE 11

PROTEIN SCIENCE 2018 VOL 27:112-128

TOOLS FOR PROTEIN SCIENCE Improvements to the APBS biomolecular solvation software suite

Elizabeth Jurrus,1 Dave Engel,1 Keith Star,1 Kyle Monson,1 Juan Brandi,1 Lisa E. Felberg,2 David H. Brookes,2 Leighton Wilson,3 Jiahui Chen,4 Karina Liles,1 Minju Chun,1 Peter Li,1 David W. Gohara,5 Todd Dolinsky,6 Robert Konecny,7 David R. Koes ,8 Jens Erik Nielsen,9 Teresa Head-Gordon,2 Weihua Geng,4 Robert Krasny,3 Guo-Wei Wei,10 Michael J. Holst,7

  • J. Andrew McCammon,7 and Nathan A. Baker

1,11*

1Pacific Northwest National Laboratory, Richland, Washington 2University of California, Berkeley, California 3University of Michigan, Ann Arbor, Michigan 4Southern Methodist University, Dallas, Texas

  • 5St. Louis University, St. Louis, Missouri

6FoodLogiQ, Durham, North Carolina 7University of California San Diego, San Diego, California 8University of Pittsburgh, Pittsburgh, Pennsylvania 9Protein Engineering, Novozymes A/S, Copenhagen, Denmark 10Michigan State University, East Lansing, Michigan 11Brown University, Providence, Rhode Island

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SLIDE 12

comparison of so>ware for molecular surface

  • 53.8

93.9

  • 40
  • 20

20 40 60 80 Surface Potential (kJ/mol/e)

MSMS NanoShaper

N = 29867, iter = 62 N = 29224, iter = 9 E_sol = -10443 kJ/mol E_sol = -10675 kJ/mol

PDBID: 3dfg

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SLIDE 13
  • utline
  • 1. protein-solvent electrostatics
  • 2. incompressible fluid flow
  • tracer transport on a sphere
  • vortex dynamics on a sphere
  • vortex dynamics in 2D
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SLIDE 14

motivation : atmosphere

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tracer transport

given : q0(x) , u(x, t) , x 2 S problem : determine q(x, t) for t > 0

Eulerian form

∂q ∂t(x, t) + u · rq(x, t) = 0

Lagrangian form

flow map : a ! x(a, t) , a 2 S ∂ ∂tx(a, t) = u(x(a, t), t) , x(a, 0) = a q(x(a, t), t) = q0(a)

tracer transport on a sphere

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SLIDE 16

Lagrangian particle method

particles : xj(t) ≈ x(aj, t) , xj(0) = aj , j = 1 : M panels : Pk(t) = x(Pk(0), t) , S = ∪N

k=1Pk(t) , k = 1 : N

icosahedral triangulation

N 20 80 320 1280 5120 20480 81920 327680 M 32 122 482 1922 7682 30722 122882 491522 ∆λ 63.43 33.87 17.22 8.64 4.33 2.16 1.08 0.54 Bosler-Kent-K-Jablonowski (2017) JCP 340

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SLIDE 17

particle advection

d dtxj(t) = u(xj, t) , xj(0) = aj qj = q0(aj)

problem : particles become disordered for t > 0 solution : remeshing : {xold

j } → {xnew j

} , {qnew

j

} = ?

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SLIDE 18

test case 1 : moving vortices flow

  • no remeshing

movie

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particle advection

d dtxj(t) = u(xj, t) , xj(0) = aj qj = q0(aj)

problem : particles become disordered for t > 0 solution : remeshing : {xold

j } → {xnew j

} , {qnew

j

} = ?

  • 1. direct remeshing

{qnew

j

} = I({xnew

j

}; {xold

j }, {qold j })

  • 2. indirect remeshing

{anew

j

} = I({xnew

j

}; {xold

j }, {aold j })

{qnew

j

} = q0({anew

j

}) I : STRIPACK/SSRFPACK (Renka 1997)

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SLIDE 20

test case 1 : moving vorZces flow

movie

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tracer error

test case 1 test case 2

0.5 1 2 4 8 16 32 10

−6

10

−5

10

−4

10

−3

10

−2

10

−1

10 ∆λ (degrees)

∞ 2

O(∆λ4) LR, l∞ LR, l2 LPM−d, l∞ LPM−d, l2 LPM−i, l∞ LPM−i, l2 0.5 1 2 4 8 16 32 10

−7

10

−6

10

−5

10

−4

10

−3

10

−2

10

−1

10 10

1

∆λ (degrees)

∞ 2

O(∆λ4) LR, l∞ LR, l2 LPM−d, l∞ LPM−d, l2 LPM−i, l∞ LPM−i, l2

∆λ = 8.64 ∆λ = 4.33 ∆λ = 2.16

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SLIDE 22

⇣(xk)Ak < ✏ Γmax

test case 1 : moving vorZces flow

  • adapZve panel refinement

movie

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test case 2 : reversing-deformational flow

  • Gaussian hills tracer

movie

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test case 2 : reversing-deformational flow

Gaussian-hills tracer , grid spacing ∆λ = 8.64 direct remeshing indirect remeshing

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SLIDE 25

tracer error

test case 1 test case 2

0.5 1 2 4 8 16 32 10

−6

10

−5

10

−4

10

−3

10

−2

10

−1

10 ∆λ (degrees)

∞ 2

O(∆λ4) LR, l∞ LR, l2 LPM−d, l∞ LPM−d, l2 LPM−i, l∞ LPM−i, l2 0.5 1 2 4 8 16 32 10

−7

10

−6

10

−5

10

−4

10

−3

10

−2

10

−1

10 10

1

∆λ (degrees)

∞ 2

O(∆λ4) LR, l∞ LR, l2 LPM−d, l∞ LPM−d, l2 LPM−i, l∞ LPM−i, l2

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SLIDE 26

vortex dynamics on a sphere (partial list!)

point vortices . . .

Kimura-Okamoto (1987), Newton-Sakajo (2007)

vortex patches . . .

Dritschel (1989, 2004), Dritschel-Polvani (1992) Crowdy-Cloke (2003), Surana-Crowdy (2008)

vortex sheets . . .

Sakajo (2009)

present work : smooth vorticity

… … …

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SLIDE 27

velocity : vorticity : Poisson equation : vortex dynamics : Coriolis parameter : f = 2Ω sin θ

∂ζ ∂t + u · r(ζ + f) = 0 u = rψ ⇥ x ζ = r ⇥ u

barotropic vorticity equation : Eulerian form

r2ψ = ζ

Bosler-Wang-Jablonowski-K (2014) FDR 46

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SLIDE 28

flow map : vorticity : stream function : Biot-Savart law : vortex dynamics :

dζ dt = −2Ωdz dt ψ(x) = − 1 4π Z

S

log(1 − x · ˜ x)ζ(˜ x)dA(˜ x) ζ = ζ(x, t) x = x(~ ↵, t) dx dt = − 1 4π Z

S

x × ˜ x 1 − x · ˜ xζ(˜ x, t)dA(˜ x)

barotropic vorticity equation : Lagrangian form

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SLIDE 29

particles :

S = ∪N

k=1Ak

panels : cubed sphere

discretization

xj(t) = x(~ ↵j, t) dζj dt = −2Ωdzj dt dxj dt = − 1 4π X

k=1 k6=j

xj × xk 1 − xj · xk ζkAk

vorticity :

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SLIDE 30

Rossby-Haurwitz wave - no remeshing

vorticity panels

movie

Rossby-Haurwitz wave – no remeshing

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SLIDE 31

RH4 wave , remesh + restart

vorticity panels

movie

Rossby-Haurwitz wave – remeshing

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SLIDE 32

remesh + refine disruption of the polar vortex

motivated by Juckes & McIntyre (1987)

movie

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SLIDE 33

fluid flow in 2D : incompressible, inviscid

Eulerian form Lagrangian form

∂ω ∂t + u · rω = 0 , r · u = 0 u = r⊥ψ , r2ψ = ω

  • parZcle/panel method + remeshing, AMR, treecode

x(a, t) , dx dt = u(x, t) , x(a, 0) = a u(x, t) = Z Kδ(x, y)ω(y, t)dy , Kδ(x, y) = r⊥ ln(|x y|2 + δ2) 4π ω(x, t) = ω0(a)

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ellipZc vortex

linear scale logarithmic scale

Koumoutsakos (1997)

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SLIDE 35

ellipZc vortex

adapZve mesh

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SLIDE 36

5 10 15

t

50 100 150 200 250 300

max(t)

(t) (t)

5 10 15

t

0.95 0.98 1 1.02 1.05

max(t) / max(0)

(t) / (0) (t) / (0))

ellipZc vortex 1 : conserved quanZZes

ωmax(t) = maxxω(x, t) Γ(t) = Z ω(x, t)dA γ(t) = Z ω2(x, t)dA

maximum vorZcity : circulaZon : enstrophy :

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SLIDE 37

thanks to my collaborators -

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SLIDE 38

Weihua Geng Ling Xu

thanks to my collaborators -

Peter Bosler

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SLIDE 39

current/future projects

protein-solvent electrostatics

  • binding energy of protein-ligand complex
  • protein pKa

incompressible fluid flow

  • viscosity, 3D, solid boundaries
  • shallow water equations