ShaunR

In the writer there is a disable structure. If you disable the currently enabled (and enable the other) it will use the previous index reading method. Does this affect the result you see?

VxWorks paths are case sensitive (windows aren't by default),

Yes. That's the tricky bit though since you cannot serialise LabVIEW objects so it's not just a case of "(un)Flatten To String" to get them across a network.. This thread on "Lapdog over the network" will highlight most of the issues (and solutions)..

You can't use a negative number with this because the indexes can be negative (strange, I know, but it is to do with wrap-around). I'm thinking that we could have a boolean with the R and Cnt (a block is converted to a cluster for processing-see the CB GetIndexes3.vi) which tells the index iterator (in the write) whether that index should be considered in the "lowest" check. This would have very little impact on performance (read a few more bytes in the block at a time and 2 AND operators.). Then you would need a "registration manager". That would be responsible for finding out how many are currently registered, updating the registered count and choosing a slot which has a F flag to give to the reader that wants to register (not disimilar to what you are currently doing). The additional difference would be that it is also capable of resizing the array if there are not enough index slots It could even shrink the array and reorganise if we wanted to be really smart so that the index iterator doesn't process any inactive slots and do away with the choosing of an inactive slot altogether. This only ever needs to happen when something registers/unregisters so even if this is locking, it will not have much of an impact during the general running (now we are starting to get to the Disruptor pattern )

Yeah. Don't want to go to a DLL. Been there, done that, torn holes in all my T-shirts. Is there no way we can utilise the callbacks (I thought that was what the InstanceDataPointer was for). That wouldn't work well for my use cases since I don't know how many I need up front (could be 10, could be 30 and may change during the program lifetime as modules are loaded and unloaded->plugins). The rest (about first call etc) is valid. It really needs to be in the next layer up but as that doesn't exist yet, its in the current read and writes. What we (or more specifically, I) don't want is for them to be reliant on shift registers in the users program to maintain the state info. How that is handled will depend whether the next layer is class based or classic labview based which is why I havn't broached it yet. At that layer, I don't envisage a user selectable "Init". More that the init is invoked on a read or write depending on what gets there first (self initialising). I ultimately want to get to a point where you just slap a write VI down and slap read VIs wherever you need them (even in different diagrams) without having to connect wires (see my queue wrapper vi for how this works, although not sure how it will in this case, ATM, since the queue wrapper uses names for multiple instances).

Indeed.I know the issues and have some ideas (easiest of which is to have a boolean in the index array cluster alongside the R and Cnt). Do you have a suggestion/method/example ?

Done. MJE mentioned this previously and, until now I have resisted since I was more concerned with absolute speed performance. But it has nasty side effects on thread constrained systems (Dual cores etc) unless they can yield. You lose performance of using subroutine on constrained CPUs and spread obviously increases as we give labview the chance to interfere. But nowhere near as much as the queue or event primitives. So you see an increase in mean and STD but the median and quartile (which I think are better indicators as they are robust to spurii) remains pretty much unchanged. I've also now modified the index reader in the write to be able to cope with an arbitrary number of multiple readers. We just need to think how we store and manage registration (a reader jumps on board when the writer is halfway through the buffer, for example). Also added the event version of the test harnesses. Version 3 is here. After this version I will be switching to a normal versioning number system (x.x.x style) as I think we are near the end of prototyping.

Take a look at Dispatcher in the CR It may provide most of your TCPIP architecture as it is publisher/subscriber and can cope with many clients/servers.

The first call (in the write) is because when everything starts up all indexes are zero. The readers only continue when the write index is greater so they sit there until the cursor index is 1. With the writer, it has to check that the the lowest reader index.isn't the same as its current write. At start-up,, when everything is zero, it is the same therefore if you don't have the First Call, it will hang on start. Once the writer and reader indexes get out of sync, everything is fine (until the I64 wraps around of course-needs to be addressed). If you have a situation where you reset all the indexes and the cursor back to zero AND it is not the first call; it will hang as neither the readers or the writer can proceed.

Indeed. Events are a more natural topological fit (as I think I mentioned many posts ago). Initially, I was afraid that the OS would interfere more with events than queues (not knowing exactly how they work under the hood, but I did know they each had their own queue). For completeness, I'll add an event test harness so we can explore all the different options.

I disagree. The processes are most certainly not parallel,even though your computations are (as is seen from the time). In your second example you are attempting to "pipeline" and now using 2 queues (I say attempting becauseit doesn't quite work in this instance). You are a) only processing 100 values instead of all 200.(true case in bottom loop never gets executed) b) lucky there is nothing in the other cases because pipelining is "hybrid" serial (they have something to say about that in the video) c) lucky that the shortest is last (try swapping the 5 with the -1 so -1 is top with a) fixed->back to 600ms) d) No different to my test harness (effectively) if you place the second enqueue straight after the bottom loops dequeue instead of after the case statement (which fixes c).

Will Smith beat up some aliens, aparently

Well. You have managed to concisely put into a paragraph or two what I have been unsuccessfully trying to get across in about 3 pages of posts . (+1).

I have faith in you !

Indeed. However a variant is constructed (constant on the diagram), but from what AQ was saying about descriptors, a simple copy is not adequate since the "void" variant has the wrong ones. I'm now wondering about the LVVariantGetContents and LVVariantSetContents which may be the correct way to modify a variants data and cause the descriptor to be updated appropriately.

Hmmmm. Not sure what this "top swap" actually is. Is that just swapping handles/pointers so basically the pointer in the buffer then points to the empty variant for a read? That would be fine for a write, but for a read the variant needs to stay in the buffer. Can you demonstrate with my original example?

Not quite.. The execution time is 500+100 (they aren't parallel processes). Unlike the buffer which is 500 (the greater of the two). Try again please

OK. Words aren't working. What is your "single queue that dequeues an element and hands it to N processes running in parallel", implementation of this?: AQ1.vi

+1. Plenty for me to play with here. Ta very muchly (did you mean 4 or 8 bytes for the pointer size rather than 8 or 16?)If the variant claims right of destruction, what happens to the copies in the buffer? Is this the reason why it crashes on deallocation?

I look at it very simplistically. The private data cluster is just a variable that is locked so you can only access it via public methods. FGV is also a variable that is locked so you can only access it with the typdef methods. In my world. There is no difference between a class and an FGV as a storage mechanism. I've got no idea what labview thinks (that's why your input is invaluable). I just want it to do what I need. If labview requires me to make a copy of an element so it is a data copy rather than shared, then I'm ok with that (LVCopyVariant, LVVariantGetContents, LVVarintSetContents et. al. docs would be useful ). But I'm not ok with a copy of an entire array for one element that causes buffer-size dependant performance. The only reason I have gone down this path is because a global copies an entire array so I can get to one element. If you have another way without using the LVMM functions then I'm all ears. I just don't see any though (and I've tried quite a few). Throw me a bone here eh?

Indeed. But it seems to lock the entire array while it does it. When I experimented, it one of the slowest methods. Ahhhh. Those were the days [misty, wavey lines]. When GPFs where what happened to C programmers and memory management was remembering what meetings to avoid. Where is this documented about SwapBlock (or anything for that matter)? I couldn't even find what arguments to use. I also found a load of variant functions (e.g. LVVariantCopy) but have no idea how to call them.

Now you have switched to byte arrays; you don't need a terminating string. But we still need to get rid of the flatten and unflatten which are too slow.

Well. You answered that in a previous post. If you remember, there was a significant change in times for different sizes of buffer-the bigger it got, the worse it was. As you pointed out. That was because the global variable array forced a copy of the entire array to access a single element. So although you are correct in that with native labview code you can "get" a single element. In reality, a copy of an entire array is required to get it (the only scenario where this isn't the case is where labview uses the "sub-array" wire). The latest version allows a buffer size as large as you want with no impact. So if you want a practical visualisation. Load up the first example and set the buffer to 10,000 and compare it to the second example with a buffer of 10,000. Agreed. Shame though You can try this yourself. Set all the read and write polymorphic instances to non-reentrant.(the write/read double, write read index etc inside the read and write VIs) You've hit an important point here though. Scalability. This scales really, really well. Make the number of readers, say, 10 and there is a marginal increase in processing time. For queues, it is a fairly linear increase. Oh. I don't know. Now that you have the buffer that doesn't need DVRs, globals, LV2 globals or singletons, it can be put into a class. Basically the incrementing counter (the feedback node in the reads) just needs to be in your private data cluster. Then you would be in a good position to figuring out how to manage the reader registration (The ID parameter) That sort of stuff is only just on the edge of my radar ATM. But nothing to stop you coming up with the class hierarchy for an API since you don't have to worry about locking/contention at that point.

This is exactly what is being achieved with the LV MM functions although we cannot get reference access, only a "copy from" since to get back into labview we need "by value."