brute force

adj. Describes a primitive programming style, one in which the programmer
relies on the computer's processing power instead of using his or her own
intelligence to simplify the problem, often ignoring problems of scale and
applying naive methods suited to small problems directly to large ones. The
term can also be used in reference to programming style: brute-force
programs are written in a heavyhanded, tedious way, full of repetition and
devoid of any elegance or useful abstraction (see also brute force and
ignorance ). The canonical example of a brute-force algorithm is associated
with the traveling salesman problem (TSP), a classical NP- hard problem:
Suppose a person is in, say, Boston, and wishes to drive to N other cities.
In what order should the cities be visited in order to minimize the distance
travelled? The brute-force method is to simply generate all possible routes
and compare the distances; while guaranteed to work and simple to implement,
this algorithm is clearly very stupid in that it considers even obviously
absurd routes (like going from Boston to Houston via San Francisco and New
York, in that order). For very small N it works well, but it rapidly becomes
absurdly inefficient when N increases (for N = 15 , there are already
1,307,674,368,000 possible routes to consider, and for N = 1000 well, see
bignum ). Sometimes, unfortunately, there is no better general solution than
brute force. See also NP- and rubber-hose cryptanalysis. A more
simple-minded example of brute-force programming is finding the smallest
number in a large list by first using an existing program to sort the list
in ascending order, and then picking the first number off the front. Whether
brute-force programming should actually be considered stupid or not depends
on the context; if the problem is not terribly big, the extra CPU time spent
on a brute-force solution may cost less than the programmer time it would
take to develop a more intelligent algorithm. Additionally, a more
intelligent algorithm may imply more long-term complexity cost and
bug-chasing than are justified by the speed improvement. Ken Thompson,
co-inventor of Unix, is reported to have uttered the epigram When in doubt,
use brute force. He probably intended this as a ha ha only serious , but the
original Unix kernel's preference for simple, robust, and portable
algorithms over brittle smart ones does seem to have been a significant
factor in the success of that OS. Like so many other tradeoffs in software
design, the choice between brute force and complex, finely-tuned cleverness
is often a difficult one that requires both engineering savvy and delicate
esthetic judgment.

