Hi,
After attending a session with Mark Proctor in London I was
inspired to play around with Drools in a slightly different way
than we use it for in the workplace, and try and solve a puzzle.
Unfortunately I couldn't get Drools to solve it as I kept getting
memory problems (I believe are cartesian joins being the problem),
so I decided to extend the golfer example to see if I got the
same problem
I added two new names and a new integer property, club
// create all possible Golfer objects
String[] names = new String[] { "Fred", "Joe",
"Bob", "Tom", "Des", "Terry" };
String[] colors = new String[] { "red", "blue",
"plaid", "orange","black", "white" };
int[] positions = new int[] { 1, 2, 3, 4, 5, 6 };
int[] clubs = new int[] {9,8,7,4,5,5};
for ( int n = 0; n < names.length; n++ ) {
for ( int c = 0; c < colors.length; c++ ) {
for ( int p = 0; p < positions.length;
p++ ) {
for ( int q = 0; q < clubs.length;
q++ ) {
session.insert(new Golfer(
names[n], colors[c], positions[p], clubs[q]) );
....
Then changed the golder.drl to:
package com.sample
import com.sample.Golfer;
rule "Golfer Riddle"
when
// A golfer named Fred,
Golfer( name == "Fred",
$fredsPosition : position, $fredsColor : color,
$fredsClub : club )
// Der Golfer hinter Fred trägt blau
Golfer( $unknownsName : name != "Fred",
$unknownsPosition : position == ( $fredsPosition
+ 1 ),
$unknownsColor : color == "blue", color !=
$fredsColor,
$unknownsClub : club == 5 )
// Joe steht an zweiter Stelle
Golfer( name == "Joe", $joesPosition : position == 2,
position != $fredsPosition,
$joesColor : color != $fredsColor,
$joesClub : club == 5 )
// Bob traegt Karo
Golfer( name == "Bob",
name != $unknownsName,
$bobsPosition : position != $fredsPosition,
position != $unknownsPosition, position !=
$joesPosition,
$bobsColor : color == "plaid",
color != $fredsColor, color != $joesColor,
color != $unknownsColor,
$bobsClub : club < $joesClub )
// Tom ist nicht 1. oder 4., traegt kein Orange
Golfer( $tomsName : name == "Tom",
$tomsPosition : position != 1, position != 4,
position != $fredsPosition, position !=
$joesPosition,
position !=
$bobsPosition,
$tomsColor : color != "orange", color != "blue",
color != $fredsColor, color != $joesColor,
color != $bobsColor )
Golfer ( $des : name == "Des", $desPosition : position <
$fredsPosition, $desColor : color != "blue",
color != $fredsColor, color != $joesColor,
color != $bobsColor )
Golfer ( $terry : name == "Terry", $terryPosition :
position < $desPosition, $terryColor : color != "blue",
color != $fredsColor, color != $joesColor,
color != $bobsColor )
then
System.out.println( "Fred " + $fredsPosition + " " +
$fredsColor );
System.out.println( "Joe " + $joesPosition + " " +
$joesColor );
System.out.println( "Bob " + $bobsPosition + " " +
$bobsColor );
System.out.println( "Tom " + $tomsPosition + " " +
$tomsColor );
System.out.println ( "Des " + $desPosition + " " +
$desColor );
System.out.println( "terry " + $terryPosition + " " +
$terryColor );
end
After a couple of minutes of processing I got:-
Exception in thread "main" java.lang.OutOfMemoryError: Java heap
space
I also changed java memory allocation with -Xms1640M -Xmx1640M
(The most I can allocate on my PC), and tried running it as a
stateless session too.
Is there anything else I can do, or is this simply pushing drools
too far (surely not!!) ?
I'm very keen on pushing this technology as much as possible in
our workplace and I'd really appreciate any help.
Thanks in advance
Simon
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