Re: Randomizing records in a file

On Mon, Jun 4, 2012 at 7:36 PM, Nathan Andelin <nandelin@xxxxxxxxx> wrote:

I have no idea why Albert may need to randomize his data.

And we still don't. But that's OK.

But we have a couple use cases.

Thanks for these; at least they are understandable and provide some
motivation for randomization. I think they are classic cases, and
probably among the main reasons randomization features exist in so
many languages (though notably absent in RPG). I probably wouldn't
use the suggestions given in this thread for these use cases, though.

Since the state is funding the school, they require that applicants be
admitted via "lottery". Generating random values and linking them to
applicants is a good way to ensure that each applicant is given an
equal chance of being admitted. Running a lottery is a simple matter
of ordering the applicant list by random value, and selecting the
applicants from the top of the list.

Maybe it is my comfort with procedural/imperative thinking and
weakness with SQL-style thinking, but to me it would be more efficient
to just generate the random numbers you need, and have these numbers
used as selectors (simplest would be record numbers). The fewer spots
and more applicants you have, the more efficient this would be.

Similar to school admissions, we have an automated process for
generating student schedules, where student course requests are
processed in random order so that if there are more course requests
than available seats, it makes the process fair for all students.

I guess this is fair enough, though this situation feels to me more
like a normal transaction problem, where requests are processed in the
order received. Granted, there's no guarantee that you won't get two
requests that, to the ability we can measure, arrive at the same time.
So some randomization is likely to be necessary, but this kind of
thing wouldn't need to be explicitly handled at the app level, it
could be taken care of transparently at the system level (whichever
request *happens* to get into the queue first gets taken first).

John