one producer two consumer loops, dequeue same element in both consumers

[Blokk]

Hi!

What is the best way for the following:

I enqueu data in my producer loop. I need this data dequeue-d in both of my consumer loops, but I want to dequeu the same element in both loops.

Of course if I put dequeues in both loop, then the second consumer loop will loose the odd elements and the first consumer loop will loose the even elements.

thanks!

[GerdW · Accepted solution]

Hi,

either create two queues or use notifiers...

[Blokk]

just one more question:

My two consumer loops have a very fast loop cycle time, and the producer loop has a slow loop time (many GPIB reads).

In this case because there is no danger to loose data, Can I just replace the queue structure with Notifiers? So I do nod have to use two queues...

Thanks!

[GerdW]

Hi Blokk,

"no danger" is quite optimistic in software development, but in this case you may use notifiers...

[Blokk]

I see 🙂

The master loop has about 12 seconds loop time, and what I do in the two slave loops with the data, will take no more than 1 second.

Thanks very much for help! 🙂

[JÞB]

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@Blokk wrote:

Hi!

What is the best way for the following:

I enqueu data in my producer loop. I need this data dequeue-d in both of my consumer loops, but I want to dequeu the same element in both loops.

Of course if I put dequeues in both loop, then the second consumer loop will loose the odd elements and the first consumer loop will loose the even elements.

thanks!

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Makes very little sence- that is, the problem is stated in such a way as to preclude an informative response

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Gerd wrote"

either create two queues or use notifiers...

Best regards,
GerdW

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Usually, Gerd gives good advice but on this one I'm going to pick on him just a bit- I bet he rushed in just a tad without thinking about the premise of the OP's question - and Gerd I don't mean to sound mean, my appologies

The question pre-supposes that to use a queue element twice in parallel it must be read twice.  This is false and led to less than optimal advice.  What about a template like shown in this snippet? 

We can certainly dequeue once and spawn as many independant actions as we need within a single consumer loop!  Much more scalable than creating a queue for each action.

[Mark_Yedinak]

A notifier however is a very effective way to broadcast a message to multiple listeners. Notifiers also scale very easily.

[Blokk]

Now I work with the notifiers, but thanks very much for the nice and simple idea with the queue! 🙂

[JÞB]

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@Mark Yedinak wrote:

A notifier however is a very effective way to broadcast a message to multiple listeners. Notifiers also scale very easily.

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Certainly correct!  and with the OP's situation where the consumers are faster than the producer a fine choice for now.  when the relative speeds become closer the notifier solution can loose data.  I intended to provide an alternate method for more general application.  Thanks for the input

[RavensFan]

Everyone,

loose = not tight

lose = not found