I have just finished Core 2 and I am excited about using message handlers with producer consumer loops. I want to know why I would use a QMH instead of a CMH. They both seem to do the same thing. If you look at the documentation in the templates, they both have the exact same text with the exception of when they use QHM or CHM. I think I understand the difference (for the most part) but I want to know the advantages of one over another. In the lesson it talked about the ability to broadcast in the CHM vs not being able to do that in the QHM. Not sure exactly what that means.

I have been using (and may have invented the name CMH) since LabVIEW 2016 (and I'm pretty sure before that Template was invented). It is probably the most heavily-used design pattern in my current code portfolio. I have found a few places where Channel Wires "go awry" (for some reason, they don't play well, for me, in the myRIO Software Toolkit), so I also fall back on the QMH (but without the template). For me, the advantage of the CMH over the QMH is mainly in the clarity of the mnemonics -- data flows (to the right) out of Channel Writers, and comes in (on the left) to Channel Readers. This encourages you to place the "Next Message" VI near the right (output) edge of the CMH Loop and "show" the data flowing out, and maybe around to come back in on the input side for the next pass through the Message-handling Loop. I also have taken advantage of branching the Message Channel Wire. Bob Schor P.S. -- if you like the CMH, and know the Producer/Consumer Design Pattern, please use the Stream Channel Wire to send data from Producer to Consumer. Its "last element?" and "valid element?" terminals provide a clean (and logical) way to implement a Sentinel to allow the Producer (who knows what data are coming in, and when the data stream has stopped) to tell the Consumer that no more data are coming, while leaving the commuunication channel intact (meaning not "releasing the Queue"). The Producer simply sends "last element?" = True (often with Valid Element = False) and exits. The Consumer simply wires "last element" to its Stop indicator (and possibly uses "Valid element" to process, or not, the last, possibly null, data element) and exit in its turn, knowing that the Producer won't be sending more data. BS

LabVIEW

When to use CHM vs QHM

Solved!

@EthanTheHut wrote:

OK now you guys have said something I finally understand. What is one of the better "QMH" template you speak of?

I am that beginner.

I got my start on the "JKI State machine" template. I use the DEV template in Messenger Library.

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LabVIEW

When to use CHM vs QHM

Re: When to use CMH vs QMH