brute force definition
<programming> A primitive programming style in which the
programmer relies on the computer's processing power instead
of using his 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 heavy-handed, 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 "travelling 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 minimise 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-complete.
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.
When applied to cryptography, it is usually known as brute
force attack.
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
operating system. 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 aesthetic judgment.
[Jargon File]
(1995-02-14)
Nearby terms:
browser « BRS « BRUIN « brute force » brute force and ignorance » brute force attack » BS
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