Subject: sort -R slow

From: Ole Tange <[email-masked]>
Date: Sat, 9 Oct 2010 14:52:41 +0200

I recently needed to randomize some lines. So I tried using 'sort -R'.
I was astonished how slow that was. So I tested how slow a competing
strategies are. GNU sort is two magnitudes slower than unsort and more
than one magnitude slower than perl:

$ time unsort file
real    0m1.388s

$ unsort --version
unsort 1.1.2

$ time perl -e 'print sort { rand() <=> rand() } <>' file
real    0m6.621s

$ time sort -R file
real    4m8.403s

$ sort --version
sort (GNU coreutils) 8.5

What is even scarier: sort without -R is faster than sort -R:

$ time sort file
real    0m53.553s

I would expect sort -R to be faster than sort and faster than Perl if
not as fast as unsort.

/Ole