Supercomputers definition

Thermodynamics and motion can be used as a base for an operational definition of the solid state. A solid is a phase below its glass- or melting-transition temperature where the molecular motion is almost completely restricted to small-amplitude vibrations. Both transitions are easily determined by thermal analysis (the operation). Recently it has become possible by simulation on supercomputers to establish the link from the microscopic thermal motion of macromolecules to the macroscopic thermal analysis. By solving the equation of motion, one can produce a detailed movie of molecular motion (see Sect 1.3.4, Fig. 1.47). At high temperature, conformational disorder is seen, i.e., the crystal can change to a condis state. Note that even the conformational motion occurs in a picosecond time scale (see Sect. 5.3.4). 

OVER the years many definitions for the notion of supercomputer have been given. Some of the most well-known are the fastest existing computer at any point in time and a computer that has a performance level that is typically hundreds of times higher than that of normal commodity computers. Both definitions have their drawbacks. In the first definition the object in question is a moving target because of the fast rate at which new computers are con-cieved and built. Therefore, with this definition it is hard to know whether a certain computer is still the supercomputer or a new, even faster one has just emerged. 

The second definition is vague because it presupposes that one can easily determine the performance level of a computer, which is by no means true, and furthermore, the performance factor that should discriminate between supercomputers and commodity computers is also not easily established. Indeed, it is not even straightforward to define what is meant by the term commodity computer. Should a supercomputer be measured against a PC, used mainly for word processing, or against a workstation used for technical computations ... 

Still, it is obvious that, whatever definition is used, one expects supercomputers to be significantly faster on any task than the computers to which one is normally exposed. In that sense the second definition is more appropriate. Therefore, we adhere mainly to this rather vague definition, with the addition that supercomputers have a special architecture to enable them to be faster than the standard computing equipment we use every day. The architecture, that is, the high-level structure in terms of its processors, its memory modules, and the interconnection network between these elements, largely determines its performance and, as such, whether or not it is a supercomputer. Other defining features of the architecture are the instruction set of the computer and the accessibility of the components in the architecture from the programmer s point of view. 

At the 1986 and 1988 Gordon Research Conferences on Computational Chemistry, we put forward a similar but more far-reaching definition Quantitative modeling of chemical phenomena by computer-implemented techniques. Further, in a review on how supercomputing is impacting the field [D. B. Boyd and K. B. Lipkowitz, Supercomputing, Spring, 23 (1988)], we went so far as to proffer that computational chemistry consists of those aspects of chemical research that are expedited or rendered practical by computers. 

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