Algorithm needed: reading/writing a large file

[Jeffrey W Percival]

In article <8137 at bsu-cs.bsu.edu> dhesi at bsu-cs.bsu.edu (Rahul Dhesi) writes:
>In article <205 at larry.sal.wisc.edu> jwp at larry.sal.wisc.edu (Jeffrey W
>Percival) writes:
>[how do I sort a large file that won't fit in memory?]
>There are many variations on the merge sort.  Here is a simple one:

Please be careful with your paraphrasing.  I did not ask how to sort a
large file that won't fit in memory.  I said I already had a fast and
efficient sort and that the sorting was already known.  My question was
about optimizing the process of rearranging a disk file according to a
*given* mapping.

One helpful person suggested reading sequentially and writing randomly,
rather than vice-versa, and I tried that but it didn't help.  I guess
the benefit gained from using the input stream buffering was cancelled
out by the effective loss of the output stream buffering.

The ever-attentive and always-reliable Mr Torek suggested looking
into disk cache algorithms in OS journals, and verily that I will do,
with thanks to those who responded.
-- 
Jeff Percival (jwp at larry.sal.wisc.edu)