ACES (computational chemistry)

Aces II (Advanced Concepts in Electronic Structure Theory) is an ab initio computational chemistry package for performing high-level quantum chemical ab initio calculations. Its major strength is the accurate calculation of atomic and molecular energies as well as properties using many-body techniques such as many-body perturbation theory (MBPT) and, in particular coupled cluster techniques to treat electron correlation. The development of ACES II began in early 1990 in the group of Professor Rod Bartlett at the Quantum Theory Project (QTP) of the University of Florida in Gainesville. There, the need for more efficient codes had been realized and the idea of writing an entirely new program package emerged. During 1990 and 1991 John F. Stanton, Jürgen Gauss, and John D. Watts, all of them at that time postdoctoral researchers in the Bartlett group, supported by a few students, wrote the backbone of what is now known as the ACES II program package. The only parts which have been taken from others were the integral packages, where the MOLECULE package of J. Almlöf, the VPROP package of P.R. Taylor, and the integral derivative package ABACUS of T. Helgaker, P. Jorgensen J. Olsen, and H.J. Aa. Jensen had been adapted for the use within ACES II and had been modified for that purpose.

The first version of ACES II had been written for CRAY supercomputers (under the unix-based operating system UNICOS) and, consequently, a lot of effort had been devoted to the exploitation of matrix-vector operations through optimized Blas-routines. However, more or less simultaneously, versions for so-called "unix-boxes" were created. The original design strategy of keeping machine-dependent code to an absolute minimum facilitated this process considerably.

In the following years, the development of new techniques was for a large part continued in Karlsruhe (1991 - 1995, e.g., development of schemes for calculating NMR shifts), Austin (since 1993, e.g., development of gradient techniques for EOM methods), Mainz (since 1995, development of analytic CC second derivatives) and Budapest (since 1997) besides ongoing work in Gainesville. The code was also ported to unix-based workstations (first IBM AIX workstations and HP, since 1996 also on DEC alpha and SGI), before at the end of the nineties LINUX versions (for x86-based PCs) have been created. As the last merge between the original Florida version of ACES II and the version maintained in Austin and Karlsruhe and later in Mainz dates back to roughly 1995, it has been decided that both versions are now separately maintained and distributed.

Aces III is a parallel implementation that was released in the fall of 2008. The effort led to definition of a new architecture for scalable parallel software called the super instruction architecture. The design and creation of software is divided into two parts:

  1. The algorithms are coded in a domain specific language called super instruction assembly language or SIAL, pronounced "sail" for easy communication.
  2. The SIAL programs are executed by a MPMD parallel virtual machine called the super instruction processor or SIP.

The ACES III program consists of 580,000 lines of SIAL code of which 200,000 lines are comments, and 230,000 lines of C/C++ and Fortran of which 62,000 lines are comments.

References

• ACES II Florida-Version Homepage
• ACES II Mainz-Austin-Budapest-Version Homepage
• ACES III Homepage
• Parallel Implementation of Electronic Structure Energy, Gradient and Hessian Calculations, V. Lotrich, N. Flocke, M. Ponton, A. Yau, A. Perera, E. Deumens, R. J. Bartlett, J. Chem. Phys, 128, 194104 (15 pages) (2008) *[1]
• CFOUR Homepage

See also

• Quantum chemistry computer programs