Science at the Frontier (1992) / Chapter Skim
Currently Skimming:
7 Computation: Beyond Theory and Experiment: Seeing the World Through Scientific Computation
7 Computation: Beyond Theory and Experiment: Seeing the World Through Scientific Computation
Pages 149-177
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 149... ...
Larry Smarr, a professor in the physics and astronomy departments at the University of Illinois at Champaign-Urbana, has traveled along the paths of both theory and experimentation. He organized the Frontiers symposium's session on computation, which illustrated the premise that computational science is not merely a new field or discipline or tool, but rather an altogether new and distinct methodology that has had a transforming effect on modern science: first, to permanently alter how scientists work, experiment, and theorize; and second, to expand their reach beyond the inherent limitations of the two other venerable approaches (Box 7.1~.
|
From page 150... ...
Smarr invoked mathematician Garrett Birkhoff's roll call of these men as predecessors to mathematician and computational pioneer John van Neumann, whose "main point was that mathematicians had nearly exhausted analytical methods, which apply mainly to /ineardifferential equations and special geometries" (Smarr, 1985, p.
|
From page 151... ...
As he surveyed the growth of computational science, however, Smarr predicted that the "rapidly increasing speed and connectivity of networks will contribute to altering how humans work with supercomputers" (p.
|
From page 152... ...
Smarr, the director of the National Center for Supercomputing Applications (NCSA) at the University of Illinois, explained that the information infrastructure built both of the machines themselves and the networks that connect them is evolving to make "it possible for researchers to tap the power of supercomputers remotely from desktop computers in their own offices and labs" (p.
|
From page 153... ...
"What is striking today," Press commented, "is that computer visualization has joined the mainstream of science. People show computer movies simply because you really cannot see what is going on without them." In fact Press believes strongly that computer modeling and visualization have become "an integral part of the science lying underneath." The computation session's participants also including Alan Huang of AT&T Bell Laboratories, Stephen Wolfram of Wolfram Research, and lean Taylor from the Department of Mathematics at Rutgers University, discussed scientific computation from several diverse points of view.
|
From page 154... ...
When the results of this analysis occurring throughout the circuit are strung together, the final outcome is as simple as the outcome of any of its individual steps on or off, 1 or 0, true or false but that outcome could represent the answer to a complex question that had been reduced to a series of steps predicated on classical logic and using the three fundamental operators. v ~ What is gained by reducing the constituent elements of the system to this simplest of all currencies 1 or 0, on or off is sacrificed, however, in computational efficiency.
|
From page 155... ...
, now basic to all computers, grew in response to the same generic challenges moving more data faster and more efficiently—that are impelling scientists like Huang "to try to build a computer based on optics rather than electronics." By today's sophisticated standards, first-generation electronic computers were mastodons: prodigious in size and weight, and hungry for vast amounts of electricity first to power their cumbersome and fragile vacuum tubes and then to cool and dissipate the excess heat they generated. The transistor in 1947 and the silicon chip on which integrated circuits were built about a decade later enabled development of the second- and third-generation machines.
|
From page 156... ...
NEW DIRECTIONS IN HARDWARE FOR COMPUTATION Computing with Light The major application of optics technology thus far has been the fiber-optic telecommunications network girding the globe. Light rays turn out to be superior in sending telephone signals great distances because, as Huang described it, with electronic communication, "the farther you go, the greater the energy required, whereas photons, once launched, will travel a great distance with no additional energy input.
|
From page 157... ...
"If you took out all the wires and replaced them with optical connections, you would still have merely an optical version of an electronic computer. Nothing would really have been redesigned in any fundamental or creative way." He reminded the audience at the Frontiers symposium of the physical resemblance of the early cars built at the turn of the century to the horse-drawn carriages they were in the process of displacing and then continued, "Suppose I had been around then and come up with a jet engine?
|
From page 158... ...
Although currently only about as powerful as a silicon chip that controls a home appliance such as a dishwasher, the optical processor may eventually enable computers to operate 1000 times faster than their electronic counterparts. It demonstrates the viability of digital optical processing technology.
|
From page 159... ...
electrical pin-outs. The greater connectivity of optics is indicated in this comparison of a VLSI bonding pad with an array of SEED optical logic gates in the equivalent amount of area.
|
From page 160... ...
You can't send two electronic signals through each other." Although the medium of laser light offers many advantages, the physical problems of manipulating it and moving it through the logic gates of ever smaller optical architectures present other challenges. In responding to them, engineers and designers have developed a remarkable technique, molecular beam epitaxy (MBE)
|
From page 161... ...
." Designers and engineers using MBE technology start with gallium arsenide as a conductor for the optical chip because electrons move through it faster than through silicon and it is inherently more capable of generating and detecting light. The process involves actually fabricating layer after layer of atomic material onto the surface of the wafer.
|
From page 162... ...
In each case, the goal of solving a particular problem drives the form of the program's instructions. A successful algorithm in mathematics or applied science provides definitive instructions for an unknown colleague to accomplish a particular task, self-sufficiently and without confusion or error.
|
From page 163... ...
Not all algorithms have such an eternal life, for the problems whose solutions they provide may themselves evolve into a new form, and new tools, concepts, and machinery may be developed to address them. Press compiled a short catalog of recent "hot" algorithms in science and asked the symposium audience to refer to their own working experience to decide whether the list represented a "great edifice or a junkpile." Included were fractals and chaos, simulated annealing, Walsh functions, the Hartley and fast Fourier transforms, fuzzy sets, and catastrophe theory.
|
From page 164... ...
The fundamental operation involves establishing a banded matrix for the given wavelet family chosen. These families are predicated on the application of a specific set of coefficient numbers which were named for Ingrid Daubechies, a French mathematician whose contributions to the theory have been seminal and are called Daub 4 or Daub 12 (or Daub X)
|
From page 165... ...
Press pointed out that early insights into the wavelet phenomenon came from work on quadrature filter mirrors, and it is even conceivable that they may help to better resolve the compromised pictures coming back from the Hubble Space Telescope. And while image enhancement and compression may be the most accessible applications right now, waveless could have other powerful signal-processing uses wherever data come by way of irregular waveforms, such as for speech recognition, in processing of the sound waves used in geological explorations, in the storage of graphic images, and
|
From page 167... ...
167 in faster magnetic resonance imaging and other scanners. Work is even being done on a device that would monitor the operating sounds of complex equipment, such as jet engines or nuclear reactors, for telltale changes that might indicate an imminent failure.
|
From page 168... ...
No highly mathematical theory alone can render such visual phenomena with the power and cogency of a picture made from evolving the shape with her original computer model (Figure 7.5~. This sophisticated dialectic between theory and computer simulation also "suggests other theorems about other surface tension functions," continued Taylor, who clearly is a theoretical mathematician running experiments on her computer, and whose results often go far beyond merely confirming her conjectures.
|
From page 169... ...
. _ Each surface energy function is specified by the equilibrium single-crystal shape (the analog of a single soapbubble)
|
From page 170... ...
He surveyed the Frontiers audience and found half of its members among his users. Mathematica is a general system for doing mathematical computation and other applications that Press called "a startlingly good tool." As such, it facilitates both numerical and symbolic computation, develops elaborate sound and graphics to demonstrate its results, and provides "a way of specifying algorithms" with a programming language that Wolfram hopes may one day be accepted as a primary new language in the scientific world, although he pointed out how slowly such conventions are established and adopted (Fortran from the 1960s and C from the early 1970s being those most widely used now)
|
From page 171... ...
194~. Cellular automata are nothing more than abstract entities arranged in one or two (conceivably and occasionally more)
|
From page 172... ...
Cellular automata involve much more than an alternative to running complicated differential equations as a way of exploring snowflake and other natural structures that grow systematically; they may be viewed as analogous to the digital computer itself. "Most of [their]
|
From page 173... ...
173 "there are many physical processes for which no such average description seems possible. In such cases differential equations are not available and one must resort to direct simulation.
|
From page 174... ...
Now, the computer in Pagels' words the ultimate "instrument of complexity" makes possible direct examination and experimentation by way of computation, the practice of which he believed might deserve to be classed as a distinct branch of science, alongside the theoretical and the experimental. When colleagues object that computer runs are not real experiments, the people that Pagels wrote about, and others among the participants in the Frontiers symposium, might reply that, in many experimental situations, computation is the only legitimate way to simulate and capture what is really happening.
|
From page 175... ...
Smarr of the National Center for Supercomputing Applications (NCSA) , computer designers intent on increasing the speed and power of their serial machines concentrated on "improving the microelectronics" of the single central processing unit (CPU)
|
From page 176... ...
Nonetheless, Smarr believes the industry is approaching a new level of supercomputing unlike anything that has gone before: "By the end of the 20th century, price drops should enable the creation of massively parallel supercomputers capable of executing 10 trillion floating-point operations per second, 10,000 times the speed of 1990 supercomputers." This astounding change derives from the massively parallel architecture, which "relies on the mass market for ordinary microprocessors (used in everything from automobiles to personal computers to toasters) to drive down the price and increase the speed of general-design chips.
|
From page 177... ...
SEEING THE WORLD THROUGH SCIENTIFIC COMPUTATION 1 77 Press, William, Brian P Flannery, Saul A
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.