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Computational Science
An emerging multi-disciplinary research area that involves the use of high performance computers to study scientific problems.
School of Computer Science
April 2002
The availability of high performance computers, graphic
workstations, and high-speed networks, coupled with major
advances in algorithms and software, has brought about a
revolution in the way scientific and engineering
investigations are carried out.
Computational scientists seek
to gain an understanding of
science principally through the
development, use and
analysis of mathematical
models on high performance
computers .
Cray T3E
Origin 3000
Computational ScienceHigh Performance Scientific ComputationThe Motivation
Electron-atom and electron-molecule collisions drive many of the key chemical and physical processes in important environments that range from plasmas to living tissue.
Most energy deposited in cells by ionizing radiation is channelled into free secondary electrons with energies between 1 eV and 20 eV(B. Boudaïffa et al., Science 287 (2000) 1658)
Secondary electrons produced by fast ion tracks in radioactive waste
Computational ScienceHigh Performance Scientific ComputationThe Motivation
Studying these electron-driven processes provides a microscopic understanding of reactions in these environments and thus helps advance many technologies that are based on these processes.
Plasma flat panel display (Fujitsu
Corp.)
Computational ScienceHigh Performance Scientific ComputationThe Physics
ground state
e- + Ai(N+1)
e- + A*j(N+1)
2e- + A+k(N)
continuum
ionizationthreshold
Electron impact excitationand ionization
r N+1
Internalregion
R-matrix Approach
Externalregion
Computational ScienceHigh Performance Scientific ComputationThe Model
Schrödinger Equation solved using propagation techniques.
(HN+1 - E)N+1 = 0
Internal Region
In each sector:
• Construct Hamiltonian matrix;• Diagonalize Hamiltonian matrix.
Propagate global R-matrix across 2-D plane.
External RegionSolve systems of coupled 2nd order inhomogeneous ODEs - propagate across a 1-D plane.
Computational ScienceHigh Performance Scientific ComputationThe Computation - internal region
Gather surface amplitudes and distribute to other processors in cluster.
Global R-matrix Store
Surface amplitudes
Gather global R-matrix from processors in cluster and store.
Compute local R-matrices.
Propagate global R-matrix.
Repeat for next energy.
Computational ScienceHigh Performance Scientific ComputationThe Computation - internal region
Gather surface amplitudes and distribute to other processors in cluster.
Global R-matrix Store
Surface amplitudes
Gather global R-matrix from processors in cluster and store.
Compute local R-matrices.
Propagate global R-matrix.
Repeat for next energy.
Surface amplitudes
Gather surface amplitudes and distribute to other processors in cluster.
Global R-matrix Store
Surface amplitudes
Compute local R-matrices.
Surface amplitudes
Propagate global R-matrix.
Gather global R-matrix from processors in cluster and store.Repeat for next energy.
Computational ScienceHigh Performance Scientific ComputationThe Computation - internal region
Gather surface amplitudes and distribute to other processors in cluster.
Global R-matrix Store
Surface amplitudes
Gather global R-matrix from processors in cluster and store.
Compute local R-matrices.
Propagate global R-matrix.
Repeat for next energy.
Surface amplitudes
Gather surface amplitudes and distribute to other processors in cluster.
Global R-matrix Store
Surface amplitudes
Compute local R-matrices.
Surface amplitudes
Propagate global R-matrix.
Gather global R-matrix from processors in cluster and store.Repeat for next energy.
Computational ScienceHigh Performance Scientific ComputationThe Computation - internal region
Gather surface amplitudes and distribute to other processors in cluster.
Global R-matrix Store
Surface amplitudes
Gather global R-matrix from processors in cluster and store.
Compute local R-matrices.
Propagate global R-matrix.
Repeat for next energy.
Surface amplitudes
Gather surface amplitudes and distribute to other processors in cluster.
Global R-matrix Store
Surface amplitudes
Compute local R-matrices.
Surface amplitudes
Propagate global R-matrix.
Gather global R-matrix from processors in cluster and store.Repeat for next energy.
Computational ScienceHigh Performance Scientific ComputationThe Computation - internal region
Gather surface amplitudes and distribute to other processors in cluster.
Global R-matrix Store
Surface amplitudes
Gather global R-matrix from processors in cluster and store.
Compute local R-matrices.
Propagate global R-matrix.
Repeat for next energy.
DO J = 1, NCHAN ETJ = ET(J) JOC = 0 IF (ETJ .LT. ZERO) JOC = 1 SKJ = SQRT(ABS(ETJ)) S2K = TWO*SKJCC INITIALISE THE RECURRENCE C DO I = 1, NCHAN DO IP1 = 1, NTASY W1(I, IP1) = ZERO W2(I, IP1) = ZERO ENDDO ENDDO IF (JOC .EQ. 1) THEN W2(J, 1) = ONE ELSE W1(J, 1) = ONE ENDIF
Computational ScienceInternational Software Library
GOBACK = .FALSE. TEMPX = X DO I = 1, NCHAN K = I*(I - 1)/2 DO J = 1, I TEMPK(I, J) = Y(J + K) TEMPK(J, I) = Y(J + K) ENDDO ENDDO ELSE
R(NOPTS) = X GOBACK = .FALSE. DO I = 1, NCHAN K = I*(I - 1)/2 DO J = 1, I KBAR(NOPTS, I, J) = Y(J + K) KBAR(NOPTS, J, I) = Y(J + K) ENDDO ENDDO
Computational ScienceInternational Software Library
With the aid of a grant from the then UK Science Research Council the Computer Physics Communications International Program Library (CPCPL) was established at Queen's University Belfast in 1969.
Now an integral part of the Elsevier Science Journal, Computer Physics Communications, the Library continues to make a significant international contribution to research through its role of storing and disseminating refereed computer programs whose descriptions have been published in the journal Computer Physics Communications.
Computational ScienceInternational Software Library
CPCPL currently holds over 1,800 computer programs contributed by scientists world-wide. Catalogued under twenty-three headings the programs represent a major international repository of computational knowledge and technique.
•Astronomy and Astrophysics•Atomic Physics•Biology and Molecular Biology•Computational Methods•Computer Algebra•Computer Languages, Hardware and Software•Condensed Matter and Surface Science•Crystallography•Databases•Electrostatics and Electromagnetics•Elementary Particle Physics•Gases and Fluids•Geophysics
•Graphics•Laser Physics•Molecular Physics and Physical Chemistry•Nuclear Physics•Optics•Plasma Physics•Programming and Publication Practice•Radiation•Reactor Systems•Statistical Physics & Thermodynamics