Re: [Condor-users] nested dags and splices

["R. Kent Wenger" <wenger@xxxxxxxxxxx>]

On Tue, 3 Feb 2009, Leandro Martelli wrote:

> Dear All,
>
> I have the following situation;
>
> P1: Program 1 runs and produces n files;
> P2: Program 2 is then executed for each individual file and produces
> output for them;
> P3: Program 3 sums the outputs of all P2 executions (therefore depends
> on all P2 executions);
>
>
> I tried with nested dags and I'm checking now splices. With nested dags
> (for step P2) I noticed that the file (the nested one - P2 in this case)
> must be already written, but in my case it's going to be written only
> after P1 completes (n is not known until the end of P1). As far as I
> understand, splices work the same way, where the complete flow must be
> fully defined at start.

So you're basically trying to use nested DAGs to deal with the fact that
you don't know n for P2 ahead of time, right?  And what you want to do is
have P1 write the DAG that will run the P2 instances?

I'm assuming that you're running a pretty recent version of DAGMan (at 
least 7.1.x).  Also, does your top-level DAG look something like this?:

    JOB P1 P1.sub
    SUBDAG EXTERNAL P2 P2.dag
    JOB P3 P3.sub
    PARENT P1 CHILD P2
    PARENT P2 CHILD P3

> Is there any other way or additional tool where I could dynamically
> configure my workflow?

Here's an idea that I think will work (but I haven't actually tried it):

1) Write a "dummy" P2.dag before you submit the top-level DAG (this is
necessary so that the nested DAG node's log file will be defined at the 
beginning of the top-level DAG run).

2) P1 overwrites P2.dag.

3) Have a POST script for the P1 node that overwrites the 
P2.dag.condor.sub file:

    condor_submit_dag -f -no_submit P2.dag

I think that should do what you want.

(Note: we're working on changes that will make this kind of thing much 
easier in the future, but they're not fully implemented yet.)

Kent Wenger
Condor Team