Re: Simple disk-based sorting method

On Apr 13, 8:40 am, s...@[EMAIL PROTECTED]
 (Citizen Bob) wrote:
> I have a disk file which contains 370,260 records of average length 60
> ASCII text characters. I need to sort them on the first 9 characters,
> which are set off from the rest by a space.
>
> Once sorted the first record looks like
> 100100100 08:35-08:39 4 0 0 1 -115 -1 75 -100 dd17.txt
> and the last one looks like
> 500900900 12:41-13:25 44 1 885 0 0 1 925 -200 dd21.txt
>
> There is not enough memory in my Win2K/SP4 system to implement the
> traditional memory-based sorting algorithms, so I need to use a method
> that is disk-file based. I have plenty of disk space.
>
> I imagine that this method would open the input disk file and begin
> reading records one at a time and performing some kind of sort
> algorithm placing the result in a tem****ary output file. Once the
> original file has been swept, the process starts over and runs again
> and again for the required number of iterations until the entire list
> is sorted in ascending order. I will implement this method in standard
> DOS-based C (Microsoft Optimizing C Compiler "cl") using the Win2K
> DVM.
>
> Suggestions and references please.
>
> --
>
> "Nothing in the world can take the place of perseverance. Talent
> will not; nothing is more common than unsuccessful men with talent.
> Genius will not; unrewarded genius is almost a proverb. Education
> will not; the world is full of educated derelicts. Persistence and
> determination alone are omnipotent."
> --Calvin Coolidge


I think a variation of Radix sort would work nicely. Any algorithms
textbook should discuss it. And the definitive reference is Knuth's
volume Sorting and Searching. This would be the comp.programming
answer, given your description of programming in C.  (newsgroups are
arranged by topic for a reason.)

OTOH, you posted this in comp.databases so I'll now assume you want a
DB oriented answer. And that answer would be to pick a DBMS that runs
on your platform (WIN2K is pretty old), load the data into a table
with primary key (pkx) being those first 9 characters, then just let
the DBMS do the sorting when you issue a command like

SELECT * FROM tablex ORDER BY pkx ;

HTH,
ed