You could try making a "function" inside your script, and having that
function call itself recursively. That way, you don't have the fork
overhead.
--ronan
> I wanted to figure out how to divide a large number of things (such as
> http://cgi.ebay.com/_W0QQitemZ170371530405 ) into several smaller
> groups that could each be formed into a cube, and I had the bright
> idea that this would be suited to a recursive program. So I whipped up
> this script. Its syntax is like so:
>
> /tmp/ball-recurse 1728 8
> # objects --^ ^-- parts
>
> and it finds the first hit (8 cubes of side 6) in about 3.5s and all
> 13 possibilities in 17-18s. The results come out sorted and uniq-ed
> automatically. Let me know where I have some inefficiency, please. I'm
> eyeing that "if" structure on lines 18-23 suspiciously, but I don't
> immediately see a problem. Is there a way to invoke sh quicker?
>
> 1 #! /bin/sh
> 2 balls=$1
> 3 parts=$2
> 4 parts_so_far=$3
> 5
> 6 if [ "z$parts_so_far" = z ] ; then # if parts_so_far is empty,
> 7 upper_bound=$balls # Way too big, but it'll do.
> 8 else
> 9 upper_bound=${parts_so_far##*\ } # last number in the list
> 10 fi
> 11
> 12 try_cubesize=1
> 13 while : ; do
> 14 balls_left=$((balls - try_cubesize * try_cubesize * try_cubesize))
> 15 if [ $balls_left -lt 0 -o $parts -lt 1 -o $try_cubesize -gt
> $upper_bound ] ; then
> 16 exit
> 17 fi
> 18 if [ $balls_left -eq 0 -a $parts -eq 1 ] ; then # balls=0 && parts=1
> 19 echo "${parts_so_far#\ } $try_cubesize"
> 20 exit
> 21 else
> 22 "$0" $balls_left $((parts - 1)) "$parts_so_far $try_cubesize"
> 23 fi
> 24 try_cubesize=$(( try_cubesize + 1 ))
> 25 done
>
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