Tuesday, July 19, 2011

HW: "Hard" and "Unsolvable"

Problem (20 points):

This problem is aimed at enhancing your understanding of “hard” and “unsolvable” problems.

In 1965, computer chip pioneer Gordon E. Moore noticed that transistor density in chips had doubled every year in the early 1960s, and he predicted that this trend would continue. This prediction, moderated to a doubling (in transistor count) every 18 months, is known as the Moore’s Law. Often times, people extend the meaning of Moore’s Law to imply that computer processing speed doubles every 18 months.

(a) According to the speed-doubling result of Moore’s Law, how many times a computer today is
faster than one ten years ago?

(b) Suppose we have a computing problem that can be solved in estimated running time on the order of n , where n is the problem size (e.g., the number of nodes in a graph). Using the same amount of time, how much bigger a problem we can solve with a computer today than with one ten years ago?

(c) Suppose we have a computing problem that can be solved in estimated running time on the order of (n^2) , where n is the problem size (e.g., the number of nodes in a graph). Using the same amount of time, how much bigger a problem we can solve with a computer today than with one ten years ago?

(d) Suppose we have a computing problem that can be solved in estimated running time on the order of (n^6), where n is the problem size (e.g., the number of nodes in a graph). Using the same amount of time, how much bigger a problem we can solve with a computer today than with one ten years ago?

(e) Suppose we have a computing problem that can be solved in estimated running time on the order of (2^n), where n is the problem size (e.g., the number of nodes in a graph). Using the same amount of time, how much bigger a problem we can solve with a computer today than with one ten years ago?

(f) For Problem 3 of Tutorial 3, someone suggested that we might solve the problem (i.e., finding
integer roots for the equation) by simply testing every possible integers. Please comment.

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