資料來源 : Free On-Line Dictionary of Computing

brute force
     
         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)