Sunday, 10 January 2010

Turing's Cathedral

Turing's Cathedral is an interesting look at computing at the 60th anniversary of John von Neumann's proposal for the digital computer. It cover aspects of computational models, biology, AI and the growing wealth of knowledge on the internet.

The quotes below show how we have far exceeded the original expectations of computation. Even though we are still programming the von Nuemann architecture / Turing machines, I have always wondered how much the languages we use would change given an entirely different computational model.

"When the machine finally became operational in 1951, it had 5 kilobytes of random-access memory: a 32 x 32 x 40 matrix of binary digits, stored as a flickering pattern of electrical charge, shifting from millisecond to millisecond on the surface of 40 cathode-ray tubes."

"By breaking the distinction between numbers that mean things and numbers that do things, von Neumann unleashed the power of the stored-program computer, and our universe would never be the same."

"In the early 1950s, when mean time between memory failure was measured in minutes, no one imagined that a system depending on every bit being in exactly the right place at exactly the right time could be scaled up by a factor of 10^13 in size, and down by a factor of 10^6 in time. Von Neumann, who died prematurely in 1957, became increasingly interested in understanding how biology has managed (and how technology might manage) to construct reliable organisms out of unreliable parts. He believed the von Neumann architecture would soon be replaced by something else. Even if codes could be completely debugged, million-cell memories could never be counted upon, digitally, to behave consistently from one kilocycle to the next."

"As organisms, we possess two outstanding repositories of information: the information conveyed by our genes, and the information stored in our brains. Both of these are based upon non-von-Neumann architectures, and it is no surprise that Von Neumann became fascinated with these examples as he left his chairmanship of the AEC (where he had succeeded Lewis Strauss) and began to lay out the research agenda that cancer prevented him from following up."

"We can divide the computational universe into three sectors: computable problems; non-computable problems (that can be given a finite, exact description but have no effective procedure to deliver a definite result); and, finally, questions whose answers are, in principle, computable, but that, in practice, we are unable to ask in unambiguous language that computers can understand."

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