Experimental Physics and
Industrial Control System

Kay-Uwe Kasemir <[email protected]> · Thu, 29 Sep 2005 12:02:48 -0400

void collectSample={
    processLink=[3] {
        {pvname = “incA”;      parallel=true;  wait=true},
        {pvname = “incB”;      parallel=false; wait=true},
        {pvname = “getSample”; parallel=false; wait=true}
    }
}

I can see that incB has parallel set to false, but will indeed be

processed in parallel (with incA).

In other words, using this syntax setting parallel to false will

stop the next link from being processed in parallel, not this link.

I fear users will keep making mistakes forever because they don't

remember if setting parallel changes this or the next link's

behaviour.

I agree that it took me two times to understand this.
I think the 'parallel' is meant as a 'execute in fork'.
So incA is forked off, incB is started 'in the same process',
then we wait for both.

What about changing the syntax a bit, so that your example reads:

void collectSample={
    processLink=[3] {
        {pvname = “incA”;      wait=no},
        {pvname = “incB”;      wait=completion},
        {pvname = “getSample”; wait=completion}
    }
}

That's misleading because we _do_ want to wait for incA (and incB)
to complete before taking a sample.

Maybe it's more obvious with a nested syntax:

void collectSample={
    processLink=[2] {
        {pvname = [2]{“incA”, "incB"}; wait=completion},
        {pvname =     “getSample”;     wait=completion}
    }
}

So incA and incB can run in parallel,  we wait for both to complete,
then getSample.

Well, one could even go one step further and include some

functionality of the seq record by allowing numbers:

void collectSample={
    processLink=[3] {
        {pvname = “incA”;      wait=no},
        {pvname = “incB”;      wait=2.5},
        {pvname = “getSample”; wait=completion}
    }
}

which would fire off incA, incB, and then getSample after waiting

for 2.5 seconds, regardless of incB's process state, finally wait

for getSample to complete.

I think that's again wrong, you do want to wait for incA and incB.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System