Hi Alan,

Thanks for replying, but I've been able to solve this problem.  Essentially, 
the problem was this:
- My goal was to have a nested workflow execute once for each element of an 
inputted depth-1 list.  Moreover, the list elements needed to execute 
one-at-a-time and in order.
- So, I sent a depth-1 list into one of the inputs of the nested workflow.  
This input accepted a single value.
- I also set the nested workflow to have a parallelism of 1, so multiple 
instances of the nested workflow couldn't run in parallel.
- When I ran the workflow, it performed implicit iteration through the list 
elements, as expected.  Usually, it also ran through the list elements in 
order.  However, when I had lots of list elements, I occasionally found that 
the list elements did not execute in order.  The way I set up the workflow, I 
guess there was no guarantee that it should, but it still surprised me.

I later fixed this problem by:
- changing the nested workflow input to accept a depth-1 list instead of a 
single value.
- I then set up the nested workflow to remove the first element of the list and 
execute using that value.
- Finally, I set up a loop on the nested workflow so that it continued to 
execute until the list size was zero.

Anyway, you no longer need to reply to this e-mail, but I would be interested 
to hear if you had any thoughts on this problem.

Thanks,
kaushik

________________________________________
From: Alan R Williams [[email protected]]
Sent: Thursday, January 02, 2014 11:57 AM
To: [email protected]
Subject: EXT :Re: [Taverna-users] Executing lists in order

On 26-Dec-13 23:14, Datta, Kaushik (IS) wrote:
> Hi everyone,

Hello

Apologies for the delay in responding.

> I am currently using Taverna Workbench 2.4.0.  In one of my workflows, I
> am passing the output from a beanshell service to either a nested
> workflow service or a tool service.  This output is in the form of a
> depth-1 list.  I want the service that accepts the list to execute the
> list sequentially, in order.

Does the service expect a list or a single value? I am guessing a single
value.

> So, I have set the parallelism of the
> accepting service to 1, and most of the time, the list executes in
> order.  However, the list occassionally executes out-of-order.

I am confused as to how what you describe can happen.

> When
> this happens, some of the earlier list elements show a "waiting for
> data" message while later list elements execute.
>
> My question is, how can I guarantee that the accepting service processes
> the incoming list in order?  I'm sure that I can come up with a complex
> hack to solve this problem, but a simple solution would be greatly
> appreciated!

Can you send an example workflow that shows this problem?

> Thanks to all for your time.
>
> -kaushik

Alan


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