Beefy Boxes and Bandwidth Generously Provided by pair Networks
P is for Practical

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
From the Not This Way department, a moral of speed:

In college, for a FORTRAN class, I was assigned the 8-queens problem. At the time I was also taking Pascal and teaching myself 8086 assembler and was a bit overwhelmed with the labwork at the end of the semester.

As the instructor explained it, the intent was to solve the problem recursively. (HINT: it's almost trivial this way. Search with google for "eight queens recursion bit arithmetic" and take the first hit for a particularly clever solution...) Anyway, I realized that I misplaced the assignment and had to do it the night before it was due. So over a 300-baud dialup into a PR1ME system (running PR1MOS 7!) with a line editor I hacked up a Brute Force solution to the problem.

I used a 8-digit octal counter, each digit representing a column and each digit value representing a row on the chessboard. Add one, check for collisions, repeat until overflow to 9 digits of octal. As a test I did a 4x4 board. This worked, then 8x8. This was terribly slow. I started it as a phantom process, logged off, and went to bed at 1am.

The next morning I went into the lab to collect the results. The most *interesting* part was that from 1am to 2am I used 58 minutes of CPU time to solve the problem. The prof was mildly amused as 1. I was the only person to present a correct solution for that class, 2. that I was the first person he'd had to solve it through BF&I and 3. I had the absolute slowest version he'd ever seen. Nontheless, I got full credit for the assignment.

And just think: on comparative hardware in 2002, it'd run in (calculating...) under 4 minutes! Hooray for Moore's law!

In reply to Re: Trying to solve N-Queens by clintp
in thread Trying to solve N-Queens by jeffa

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or or How to display code and escape characters are good places to start.
Log In?

What's my password?
Create A New User
Domain Nodelet?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others musing on the Monastery: (3)
As of 2021-12-04 13:19 GMT
Find Nodes?
    Voting Booth?
    R or B?

    Results (30 votes). Check out past polls.