For those that donít know, the new algorithm supports a detailed trace mode. Create a logback.xml and set the level to trace. 
<logger name="org.drools" level="trace"/>

Youíll then get outputs like the following, which shows you what rules fired and when, and with what amounts of data for each node. It also shows you when rules are linked and unlinked.

2014-02-25 05:00:16,023 [main] DEBUG Starting Engine in PHREAK mode
2014-02-25 05:00:16,084 [main] TRACE Adding Rule R1
2014-02-25 05:00:16,088 [main] TRACE Adding Rule R2
2014-02-25 05:00:16,134 [main] TRACE Insert [fact 0:1:1708041420:1708041420:1:DEFAULT:NON_TRAIT:org.drools.compiler.integrationtests.Misc2Test$Foo@65cea4cc]
2014-02-25 05:00:16,142 [main] TRACE LinkNode notify=false nmask=1 smask=1 spos=0 rules=
2014-02-25 05:00:16,142 [main] TRACE   LinkSegment smask=2 rmask=2 name=R2
2014-02-25 05:00:16,146 [main] TRACE LinkNode notify=true nmask=1 smask=1 spos=0 rules=[RuleMem R1], [RuleMem R2]
2014-02-25 05:00:16,147 [main] TRACE Insert [fact 0:2:281271144:281271144:2:DEFAULT:NON_TRAIT:org.drools.compiler.integrationtests.Misc2Test$Foo2@10c3db68]
2014-02-25 05:00:16,148 [main] TRACE BetaNode insert=1 stagedInsertWasEmpty=true
2014-02-25 05:00:16,148 [main] TRACE LinkNode notify=true nmask=2 smask=3 spos=0 rules=[RuleMem R1], [RuleMem R2]
2014-02-25 05:00:16,148 [main] TRACE   LinkSegment smask=1 rmask=1 name=R1
2014-02-25 05:00:16,149 [main] TRACE   LinkSegment smask=1 rmask=3 name=R2
2014-02-25 05:00:16,149 [main] TRACE     LinkRule name=R2
2014-02-25 05:00:16,161 [main] TRACE Queue RuleAgendaItem [Activation rule=R2, act#=0, salience=0, tuple=null]
2014-02-25 05:00:16,161 [main] TRACE Queue Added 1 [Activation rule=R2, act#=0, salience=0, tuple=null]
2014-02-25 05:00:16,161 [main] TRACE Added R2 to eager evaluation list.
2014-02-25 05:00:16,162 [main] TRACE Rule[name=R2] segments=2 TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,162 [main] TRACE      1 [JoinNode(5) - [ClassObjectType class=org.drools.compiler.integrationtests.Misc2Test$Foo2]] TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,163 [main] TRACE      Segment 0
2014-02-25 05:00:16,163 [main] TRACE      1 [JoinNode(5) - [ClassObjectType class=org.drools.compiler.integrationtests.Misc2Test$Foo2]] TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,167 [main] TRACE      rightTuples TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,168 [main] TRACE      Segment 1
2014-02-25 05:00:16,168 [main] TRACE        2 [NotNode(9) - [ClassObjectType class=org.drools.compiler.Person]] TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,169 [main] TRACE        Segment 1
2014-02-25 05:00:16,169 [main] TRACE        2 [NotNode(9) - [ClassObjectType class=org.drools.compiler.Person]] TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,169 [main] TRACE        rightTuples TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,171 [main] TRACE          3 [RuleTerminalNode(10): rule=R2] TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,171 [main] TRACE          Segment 1
2014-02-25 05:00:16,171 [main] TRACE          3 [RuleTerminalNode(10): rule=R2] TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,172 [main] TRACE Fire "R2" 
[[ R2 active=false ] [ null
[fact 0:2:281271144:281271144:2:DEFAULT:NON_TRAIT:org.drools.compiler.integrationtests.Misc2Test$Foo2@10c3db68]
[fact 0:1:1708041420:1708041420:1:DEFAULT:NON_TRAIT:org.drools.compiler.integrationtests.Misc2Test$Foo@65cea4cc] ] ]
2014-02-25 05:00:16,177 [main] TRACE Update [fact 0:2:281271144:281271144:3:DEFAULT:NON_TRAIT:org.drools.compiler.integrationtests.Misc2Test$Foo2@10c3db68]
2014-02-25 05:00:16,178 [main] TRACE   LinkSegment smask=1 rmask=1 name=R1
2014-02-25 05:00:16,178 [main] TRACE   LinkSegment smask=1 rmask=3 name=R2
2014-02-25 05:00:16,178 [main] TRACE     LinkRule name=R2
2014-02-25 05:00:16,178 [main] TRACE Added R2 to eager evaluation list.
2014-02-25 05:00:16,179 [main] TRACE Insert [fact 0:3:1226345699:-62068830:4:DEFAULT:LEGACY_TRAITABLE:[Person name='null age='0' likes='null']]
2014-02-25 05:00:16,179 [main] TRACE BetaNode insert=1 stagedInsertWasEmpty=true
2014-02-25 05:00:16,179 [main] TRACE LinkNode notify=true nmask=1 smask=1 spos=1 rules=[RuleMem R1]
2014-02-25 05:00:16,180 [main] TRACE   LinkSegment smask=2 rmask=3 name=R1
2014-02-25 05:00:16,180 [main] TRACE     LinkRule name=R1
2014-02-25 05:00:16,180 [main] TRACE Queue RuleAgendaItem [Activation rule=R1, act#=2, salience=0, tuple=null]
2014-02-25 05:00:16,180 [main] TRACE Queue Added 1 [Activation rule=R1, act#=2, salience=0, tuple=null]
2014-02-25 05:00:16,181 [main] TRACE LinkNode notify=true nmask=1 smask=1 spos=1 rules=[RuleMem R2]
2014-02-25 05:00:16,181 [main] TRACE   LinkSegment smask=2 rmask=3 name=R2
2014-02-25 05:00:16,181 [main] TRACE     LinkRule name=R2
2014-02-25 05:00:16,181 [main] TRACE Added R2 to eager evaluation list.
2014-02-25 05:00:16,181 [main] TRACE Rule[name=R2] segments=2 TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,182 [main] TRACE      4 [JoinNode(5) - [ClassObjectType class=org.drools.compiler.integrationtests.Misc2Test$Foo2]] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,182 [main] TRACE      Segment 0
2014-02-25 05:00:16,182 [main] TRACE      4 [JoinNode(5) - [ClassObjectType class=org.drools.compiler.integrationtests.Misc2Test$Foo2]] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,183 [main] TRACE      rightTuples TupleSets[insertSize=0, deleteSize=0, updateSize=1]
2014-02-25 05:00:16,183 [main] TRACE      Segment 1
2014-02-25 05:00:16,183 [main] TRACE        5 [NotNode(9) - [ClassObjectType class=org.drools.compiler.Person]] TupleSets[insertSize=0, deleteSize=0, updateSize=1]
2014-02-25 05:00:16,184 [main] TRACE        Segment 1
2014-02-25 05:00:16,184 [main] TRACE        5 [NotNode(9) - [ClassObjectType class=org.drools.compiler.Person]] TupleSets[insertSize=0, deleteSize=0, updateSize=1]
2014-02-25 05:00:16,184 [main] TRACE        rightTuples TupleSets[insertSize=1, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,184 [main] TRACE UnlinkNode notify=true nmask=1 smask=0 spos=1 rules=[RuleMem R2]
2014-02-25 05:00:16,185 [main] TRACE   UnlinkSegment smask=2 rmask=1 name=[RuleMem R2]
2014-02-25 05:00:16,185 [main] TRACE     UnlinkRule name=R2
2014-02-25 05:00:16,185 [main] TRACE Added R2 to eager evaluation list.
2014-02-25 05:00:16,185 [main] TRACE          6 [RuleTerminalNode(10): rule=R2] TupleSets[insertSize=0, deleteSize=1, updateSize=0]
2014-02-25 05:00:16,186 [main] TRACE          Segment 1
2014-02-25 05:00:16,186 [main] TRACE          6 [RuleTerminalNode(10): rule=R2] TupleSets[insertSize=0, deleteSize=1, updateSize=0]
2014-02-25 05:00:16,187 [main] TRACE Rule[name=R2] segments=2 TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,187 [main] TRACE      7 [JoinNode(5) - [ClassObjectType class=org.drools.compiler.integrationtests.Misc2Test$Foo2]] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,188 [main] TRACE      Skip Segment 0
2014-02-25 05:00:16,188 [main] TRACE        Segment 1
2014-02-25 05:00:16,188 [main] TRACE        7 [NotNode(9) - [ClassObjectType class=org.drools.compiler.Person]] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,188 [main] TRACE        rightTuples TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,188 [main] TRACE          8 [RuleTerminalNode(10): rule=R2] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,189 [main] TRACE          Segment 1
2014-02-25 05:00:16,189 [main] TRACE          8 [RuleTerminalNode(10): rule=R2] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,189 [main] TRACE Rule[name=R2] segments=2 TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,189 [main] TRACE      9 [JoinNode(5) - [ClassObjectType class=org.drools.compiler.integrationtests.Misc2Test$Foo2]] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,190 [main] TRACE      Skip Segment 0
2014-02-25 05:00:16,190 [main] TRACE        Segment 1
2014-02-25 05:00:16,190 [main] TRACE        9 [NotNode(9) - [ClassObjectType class=org.drools.compiler.Person]] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,191 [main] TRACE        rightTuples TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,191 [main] TRACE          10 [RuleTerminalNode(10): rule=R2] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,191 [main] TRACE          Segment 1
2014-02-25 05:00:16,191 [main] TRACE          10 [RuleTerminalNode(10): rule=R2] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,192 [main] TRACE Rule[name=R1] segments=2 TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,192 [main] TRACE      11 [JoinNode(5) - [ClassObjectType class=org.drools.compiler.integrationtests.Misc2Test$Foo2]] TupleSets[insertSize=0, deleteSize=0, updateSize=0]
2014-02-25 05:00:16,192 [main] TRACE      Skip Segment 0
2014-02-25 05:00:16,192 [main] TRACE        Segment 1
2014-02-25 05:00:16,192 [main] TRACE        11 [JoinNode(7) - [ClassObjectType class=org.drools.compiler.Person]] TupleSets[insertSize=0, deleteSize=0, updateSize=1]
2014-02-25 05:00:16,193 [main] TRACE        rightTuples TupleSets[insertSize=1, deleteSize=0, updateSize=0]

java.lang.NullPointerException
at org.drools.core.util.index.LeftTupleIndexHashTable.remove(LeftTupleIndexHashTable.java:386)
at org.drools.core.phreak.RuleNetworkEvaluator.doUpdatesReorderLeftMemory(RuleNetworkEvaluator.java:799)