Rule gets applied once, but not again

[Ali Kheradmand]

I have a configuration like this:

<T>
...
<nodes>
<node> <id> 0 </id> <k> @nextPacket ... </k> <in> packet </in> ... </node>
<node> <id> 1 </id> <k> @nextPacket ... </k> <in> . </in>  ... </node>
...
</nodes>
</T>

And I have a rule like this

rule <k> @nextPacket => @dostuff(packet) ... </k>
     <in> packet => . </in>

The rule seems to work for node 0, the execution proceeds to a configuration like this

<T>
...
<nodes>
<node> <id> 0 </id> <k> @nextPacket ... </k> <in> . </in> ... </node>
<node> <id> 1 </id> <k> @nextPacket ... </k> <in> packet </in>  ... </node>
...
</nodes>
</T>

(note that packet is now at node 1)

But it seems the execution stops here and does not continue.

[Ali Kheradmand]

@cos @daejunpark

I tried to create a simplified version of the problem and here it is:

module TEST
    configuration
    <T>
        <xx> @init($PGM:Program) </xx>
        <nodes>
            <node multiplicity="*">
                <id> .K </id>
                <k> .K </k>
                <bin> .List </bin>
                <bout> .List </bout>
            </node>
        </nodes>


    </T>

    syntax Program ::= "www"

    syntax KItem ::= "$p" "(" List "," Int ")"

    syntax KItem ::= "@init" "(" Program ")" | "@nextPacket"

    syntax KItem ::= "@val" "(" Int ")"

    rule <xx> @init ( _:Program ) => . </xx>

         <nodes>
             (.Bag =>
                <node>
                 <id> 0 </id>
                 <k> @nextPacket </k>
                 <bin> ListItem($p(ListItem(@val(100)),1)) </bin>
                 ...
                </node>)
             (.Bag =>
                 <node>
                  <id> 1 </id>
                  <k> @nextPacket </k>
                  ...
                 </node>)
         ...
         </nodes>

    rule <k> @nextPacket => .K </k>
         <bin> (ListItem($p(P:List,Port:Int)) => .) _:List </bin>
         <bout> _:List (.List => ListItem($p(P,Port +Int 1))) </bout>

    rule <node> <bout> (ListItem($p(P:List,Port:Int)) => .) _:List </bout> ... </node>
         <node> <bin> .List => ListItem($p(P,Port)) </bin> ... </node>
endmodule

And here are the steps that are taken:

KDebug> peek
initTCell ( .Map $STDIN |-> "" $IO |-> "off" $PGM |-> www )
KDebug> step
1 Step(s) Taken.
KDebug> peek
<T> <xx> . </xx> <nodes> <node> <id> 0 </id> <k> @nextPacket </k> <bin> ListItem ( $p ( ListItem ( @val ( 100 ) ) , 1 ) ) </bin> <bout> .List </bout> </node> <node> <id> 1 </id> <k> @nextPacket </k> <bin> .List </bin> <bout> .List </bout> </node> </nodes> </T>
KDebug> step
1 Step(s) Taken.
KDebug> peek
<T> <xx> . </xx> <nodes> <node> <id> 0 </id> <k> . </k> <bin> . </bin> <bout> ListItem ( $p ( ListItem ( @val ( 100 ) ) , 2 ) ) </bout> </node> <node> <id> 1 </id> <k> @nextPacket </k> <bin> .List </bin> <bout> .List </bout> </node> </nodes> </T>
KDebug> step
1 Step(s) Taken.
KDebug> peek
<T> <xx> . </xx> <nodes> <node> <id> 0 </id> <k> . </k> <bin> . </bin> <bout> . </bout> </node> <node> <id> 1 </id> <k> @nextPacket </k> <bin> ListItem ( $p ( ListItem ( @val ( 100 ) ) , 2 ) ) </bin> <bout> .List </bout> </node> </nodes> </T>
KDebug> step
Attempted 1 step(s). Took 0 steps(s).
Final State Reached

The same rule:

    rule <k> @nextPacket => .K </k>
         <bin> (ListItem($p(P:List,Port:Int)) => .) _:List </bin>
         <bout> _:List (.List => ListItem($p(P,Port +Int 1))) </bout>

Does not get applied the second time

[Ali Kheradmand]

Actually the simplified example was fixed by changing . to .List. But doing so did not solve the problem in the actual program.
The actual rules are like this:

rule <k> @nextPacket => @parse&ingress ~> @egress ~> @txenPacket ~> @nextPacket ... </k>
     <buffer> <bin> (ListItem($packet(P:List, Port:Int)) => .List) _:List </bin> ... </buffer>

rule <topology> ... $node_port(SN:Int,SP:Int) |-> $node_port(DN:Int,DP:Int) </topology>
     <node> <nodeId> SN </nodeId> <bout> (ListItem($packet(P:List,SP)) => .List) _:List </bout> ... </node>
     <node> <nodeId> DN </nodeId> <k> @nextPacket ... </k> <bin> .List => ListItem($packet(P,DP)) </bin> ... </node>

[Ali Kheradmand]

The problem somehow got mysteriously fixed by itself after changing some irrelevant parts of the semantics!

[Radu Mereuta]

I remember having a similar issue some time ago.
Unfortunately is not something in the front end, and I don't know where to look in the backend.