ACRES (Adaptive Coordinate Real-space Electronic Structure)
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Principal Contact Person and Organization (including e-mail address):
Dr. Umesh V. Waghmare /
Prof. Efthimios Kaxiras
Department of Physics
Cambridge, MA 02138
Brief Description of Application:
Performs quantum mechanical calculations for atoms, molecules and solids based on the Density
Functional Theory (DFT). These calculations are performed on a real space mesh which is
adapted to suit spatially inhomogeneous requirements of resolution for an accurate description of
a system. Results include electronic structure, total energy and Hellman-Feynman forces on
atoms. Using the forces, the code also performs structural relaxation to minimum energy energy
Number of Lines of Code: 15,000
Target Platforms and HPF Compilers Used:
Coding Styles (data decompositions, computational methods):
Most of the arrays of rank >= 3 are block-distributed on a 3-dimensional array of processors;
part of an array that depends on the real space adaptive coordinate is distributed. Various tasks in
the calculation involve: (a) Poisson equation solver (b) Eigen value (and vector) solver for
Hermitian matrices based on Lanczos (we also tried Inverse-iteration and Conjugate-gradients).
(c) Nonlocal potentials are treated in a separable form.
Extrinsic Interfaces Used (and reasons):
We use extrinsic interfaces with PGHPF subroutines designed to perform certain tasks locally on
a processor (SPMD). This has made some parts of the calculation (eg. interpolation of data sets
on to a grid) very efficient, which could not be done so well using SIMD instructions.
Performance Information, if Available (including any possible comparisons to MPI and/or OpenMP):
(Data from an old version of ACRES; dated March 1998).
Calculations for (010) surface of MoO_3. Each calculation consists
of 2 Mo atoms and 6 O atoms inside a supercell of size
(34 * 7 * 7.5 au) which contains a vacuum of length ~ 27 au.
4 processors on O2K, time=6:14:0
8 processors on O2K, time=3:27:0
16processors on O2K, time=2:09:0