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TRANSCRIPT
NAMD -‐ The Engine for Large-‐Scale Classical MD Simula:ons of Biomolecular Systems
Based on a Polarizable Force Field
Yun (Lyna) Luo, Wei Jiang, James Phillips PI: Benoit Roux
May 16, 2013 Early Science Program Inves:gators Mee:ng
• Benoit Roux (NAMD_esp PI)
• Wei Jiang, Ray Loy (ALCF, ANL)
• Klaus Schulten, James Phillips (NAMD group, UIUC)
• Sameer Kumar (charm++ op:miza:on on BGQ, IBM)
• Mikolai Fajer, Lei Huang, Albert Lau, Janamejaya Chowdary (U Chicago)
• Alex MacKerell, Pedro Lopes, Jihyun Shim, Jin Huang (CHARMM Force Field group)
Molecular dynamics (MD) simula:on: Computa)onal approach to study conforma)onal
sampling, es)mate free energies and more
€
x(t + Δt) = x(t) +dx(t)dt
Δt +12d2x(t)dt 2
Δt 2 + .....
€
−dVdxi
= mid2xidt 2
= Forcei
CHARMM addi:ve poten:al energy func:on
€
V ( R ) = Kb(b − b0)
2bonds∑ + Kθ (θ −θ0)
2angles∑ + Kφ 1+ cos(nφ −δ)[ ]
dihedrals∑
+ Kub(S − S0)2
1,3pairs∑ + Kw (w − w0)
2improper∑
+ cijφ − φL
Δφ
(
) * *
+
, - -
j=1
4
∑i=1
4
∑i−1ψ −ψL
Δψ
(
) * *
+
, - -
j−1(
)
* *
+
,
- -
CMAP∑
+ εij
Rmin,ijrij
(
)
* *
+
,
- -
12
− 2Rmin,ij
rij
(
)
* *
+
,
- -
60
1
2 2 2
3
4
5 5 5 nonbonded
∑ +qiq j4πDrij
Founda:on for the polarizable force field
Classical Drude oscillator based polarizable force field
• Classical Drude oscillator model takes into account the electronic polarizability in molecular systems.
E + -‐
E
qD -‐qD
d
kD
( ) ( )D
2D
kAqA =α
€
q(A) = qc (A) + qD (A)
( ) ( ) ( ) ( )( ) ( )∑∑∑ −+
−
⋅+
−
⋅=
<<
DDD 2DD
DD
DD,
D
D
21)()()()( N
A
N
BA
NN
BA
cDrude AAk
BABqAq
BABqAqU rr
rrrr
Drude model implemented in NAMD: Tests on Blue Gene
A) Cubic box of 72000 water molecules (ratio 1:2) B) Cubic box of 8576 decane molecules (ratio 1:1.6) C) Cubic box of 18944 NMA molecules (ratio 1:1.8)
Jiang, W., Hardy, D., Phillips, J., MacKerell, Jr., A.D., Schulten, K., Roux, B. J. Phys. Chem. Le,., 2, 2011.
Towards Macromolecules
• Nucleic acids: DNA and RNA • Lipids: DPPC monolayer, bilayer • Proteins: Alanine dipep:de, (Ala)5, (ALA)7, (AAQAA)3, Baldwin pep:des, TripZip pep:de
10 sets of new parameters 1 model systems 298k to 398k 100 ns per replica
10*1*100*100 ns =100 μs !
Valida:ng new force field requires supercomputer and efficient sampling algorithm!
Single copy run has scaling limit (100 atoms/core) Ensemble run that launches large number of copies concurrently
Replica 1
Replica 2
Replica 3
Replica 4
accept
reject
• Different Temperature or Hamiltonian (order parameters) • Metropolis criterion to guarantee Boltzmann distribu:on • Enhance sampling and free energy convergence
Go beyond single copy simula:on scaling limit!
Okamoto and Sugita 1999
Mul:ple Copy Algorithm (MCA)
Replica Exchange Molecular Dynamics (REMD):
Jiang W, Hodoscek M, Roux, J. Chem. Theory Comput, 2009. Jiang W and Roux B. J Chem Theory Comput, 2010. Jiang, W., Luo, Y. et al., J. Chem. Theory Comput. 2012.
Implementa:ons
Distributed Replica (REPDSTR) module on CHARMM
Mul)-‐dimensional REMD on CHARMM
MPI-‐based MCA on NAMD (mpi_subcommunicator)
PAMI-‐based MCA on NAMD
(generic implementa)on)
Previous implementa:on New implementa:on
Driven by external job script (small cluster)
MPI based (supercomputer)
Small number of replicas (<100) Thousands of replicas
Low frequent exchange (<1ps-‐1 ) High frequent exchange (>0.1 ps-‐1)
One dimensional exchange Mul: dimensional exchange
Newly Implemented REMD in NAMD2.9
• Communica:on overhead is minimized by swapping order parameters instead of coordinates
• Pthread is implemented in charm++ to take advantage of the mul:ple hardware threads feature
Scalability on Mira
1024 replicas on Mira (smp mode, 16 MPI rank per node) 130k atoms per replica
Each rack contains 1024 nodes, each node contains sixteen 1.6 GHz core processors.
full-‐length c-‐Src kinase in solu:on (141095 atoms)
Generality and Flexibility
• Can be used with variant of MCA algorithms without changing the source code – T-‐REMD: temperature replica exchange
– FEP/REMD: free energy perturba:on replica exchange
– US/REMD : umbrella sampling replica exchange
– REXAMD: accelerated molecular dynamics replica exchange (Mikolai)
– String Method with Swarms-‐of-‐trajectories (Mikolai)
– Others…
• Tcl script allows user to define exchange parameters (temperature, lambda or biasing poten:al in ColVars module)
• User-‐defined exchange topology: replica_neighbors Tcl
• Easy post processing: history file, sortreplicas
Mel:ng Curve Data of 3 Baldwin pep:des TREMD using CHARMM c36 ff
Frac)on of α-‐helix is determined by >=3 residues in the α region of the Ramachandran map (-‐100<phi<-‐30 and -‐67<psi<-‐7 ). Analysis is done using the last 14 ns trajectories (STD: last seven 2 ns blocks).
Bad CMAP
vs.
Good CMAP
300 350 400 450Temperature (K)
0
0.02
0.04
0.06
0.08
0.1
Hel
ix C
onte
ntDrudeC36
ala7 T-REMD in solution
ALA7 TREMD in solu:on
NAMD/Charm++ with MPI-‐level mul:ple copy algorithms (MCAs) • Extremely scalable • Generality and Flexibility • Easy Post Processing
Drude oscillator polarizable force field • Take advantage of MPI implementa)on • Gefng towards the macromolecules
Conclusion
GePng both algorithms and new genera:on force field ready for Exascale compu:ng!