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Maksim Kuznetsov

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Maksim Kuznetsov last won the day on April 30 2017

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About Maksim Kuznetsov

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    LabVIEW 2018
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    2011

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  1. Hello everybody, I am currently cleaning up my projects and thought of the way that could potentially reduce the amount of things loaded in the development environment. This is the architecture used at the moment: Actor named "Main" launches actors A, B, C, D, E. The last actor E is launched and requires addresses of C, D. I pass these addresses (C, D) as specific actor references. That means that if I want to debug just actor E, the development environment will load actors C, D as well. And if one of them is broken, actor E will appear broken as well (even if I don't want to test functions related to C, D). Idea: Instead of passing specific actor references to actor E, I can use generic references for C, D (Actor type 2\Actor type2.lvclass) in actor E. Then if I want to work on actor E, actors C, D won't be loaded. _______________________________________________________________ Before implementing this idea for my project which will take substantial time, I would like to hear your opinion on this. Maybe I am missing something. Thank you in advance!
  2. Thank you for your feedback. The honest reason why I am asking is a hope that someone will tell me which approach from many is the better one. Every now and then I am having a dispute over this with my colleagues and I am always saying that typedefs create additional coupling, but I realised that I never understood what it actually means, it was like a rule I used throughout my projects. Now I am not sure if I was right or wrong, clearly I have a lack of knowledge. Maybe someone can share their approach and reasons behind it? Thank you!
  3. Hello James, There is a concept I am struggling to get my head around. For a long time I am following a method of not having typedefs in messages. Messages can contain various data and to make sure that the message is constructed correctly I have to consult the actor and copy the structure from it. Same applies for messages received. I believe this is called "zero-coupling". 1. If I am adding the actor reference to the VI, it brings all the dependencies of the actor to project, so I am becoming coupled to that actor, isn't it? (it is not like some generic reference) 2. Why in this case it is not advised to use actor's typedefs in messages (this could save time and less errors would appear during development)? 3. There is another method - to have a SubVI instead of typedef that will do the job of constructing (deconstructing) the message. But how is this different from using a typedef? SubVIs will also create more coupling. I have a feeling that my understanding of coupling is not full. It would be great to hear your thoughts about these points. Thank you! Kind regards, Max
  4. Thank you once again Dr. Powell for sharing this powerful approach. I can see it being used in "Metronome" actor (e.g. Set Period). And I already started to use it in my projects. If you don't mind I would like to ask you another question: I have an actor (A) that launches a sub-actor (B) to delegate some tasks to it. When sub-actor (B) publishes an event, actor (A) gets a message. However I would like to publish that message beyond actor (A). So that actors subscribed to actor (A) would also receive events from sub-actor (B). Currently my approach is to send Observer Registry of actor (A) to sub-actor (B) during initialisation. Then sub-actor (B) publishes its events into Observer Registry of actor (A) directly. Another idea was to republish the event from actor (A) when it gets the message from sub-actor (B). Neither of these methods feel right to me. The first one shares internal reference of the actor (A). The second method is not as efficient (receives, then sends again). How would you approach this?
  5. Hello, I have a little question about programming style. What do you think of using typedefs for message data? On the one hand when type changes in once place, all actors will get an update. On the other hand it creates additional coupling between actors. I am not sure what approach is better and why. Thank you!
  6. I am now thinking of creating PPL for a Messenger Library, that is the best solution. I remember 2 years ago you suggested: Creating a PPL and relinking VIs in existing actors to that PPL should work. However how would you approach creating the PPL that will also appear in LabVIEW palette for development (as it is now with Messenger Library)? I would like to distribute PPL to developers seamlessly without having them to dig into the PPL and look for particular VIs.
  7. Yes, Dr Powell, this is exactly what I was trying to do. Thank you for diagrams. I also realised it is not possible and shouldn't be possible based on this discussion: https://forums.ni.com/t5/LabVIEW-Idea-Exchange/Allow-type-casting-between-classes-types-in-PPLs-lvlibp-s-or/idi-p/3136231?profile.language=en Why it was necessary? Due to how TestStand Interacts with LabVIEW application instances: http://www.ni.com/product-documentation/14335/en/ TestStand steps tend to use the same application instance as LabVIEW executable (based on Messenger Library), this is why steps that used Messenger Library from another location didn't work. I wanted steps to be easily distributable, so had to keep dependencies (including Messenger Library) next to them. NI suggests to keep LabVIEW steps in PPL, that didn't work for me because it changed the namespace of the library. However, as you suggested, also changing namespace of the actor I communicate to, worked! So now I have two PPLs with exactly same names, but with different contents. One with actor, second with steps. Additionally, to make TestStand use a different application instance I specified a project path for each step (it forces it to use another application instance). Then I continued my experiments and included steps directly into the Actor PPL and it also worked perfectly without having multiple PPLs. Just one Actor PPL, that has API VIs that are called from TestStand. So far so good, it works well. Thank you very much! It is a relief and I learnt valuable things. P.S. Sharing PPL Messenger Library should also work, it will involve a little bit of extra work.
  8. It is a good analogy. It is unfortunate that changing namespace affects the class names and hence brakes the communication. However for my particular task it is essential. I will try to remove the namespace from flattened address and see what happens. Thank you for all of your assistance and support. I highly appreciate it.
  9. I haven't done that because the main idea was to actually have a separate namespace for a ppl and for the executable. It is unavoidable.
  10. To eliminate the misunderstanding. I have 2 applications: One is a built executable, uses messenger library as is from VI package manager. Second is a ppl with one actor inside (possible on a completely different PC). I can't make these 2 applications communicate through a TCP messenger. I understand that PPL changes the namespace of all classes. Hence when flattening/unflattening messenger addresses the namespace is included. That is why communication doesn't work. To solve this I think I need to somehow remove the namespace when flattening and then add it when unflattening (in actor that runs from PPL). What do you think?
  11. Thank you for the link. But, the problem appear even if I just have a single Actor that uses dependencies from ppl. Basically as soon as "Messenger Library" is put in ppl or a library the TCP Messenger brakes (I can send message without reply, but I can't receive replies). Apparently PPL also creates a namespace for everything that is inside and that brings us back to your reply: Is there any easy fix that I can apply to make Messenger Library work from ppl and library? Kind Regards. Maksims
  12. Hi everybody. After couple of more days of thinking and trying, I managed to narrow down the issue to a very simple experiment. Making it work will solve the problem I've been facing for many days. Experiment setup: 1. Create a simple Actor with a TCPEventMessenger (server). Make it reply with some text to the incoming message. 2. Create another Actor that connects to the actor from step 1 (through TCP). Make it send a message (with reply). 3. Add actor from step 2 to project library. 3. Test both actors in development environment, they should communicate perfectly. 4. Create a packed library build specification for project library from step 3. 5. Now open the actor from the freshly built .lvlibp and try to run it. It should fail with a timeout error while waiting for a reply. This behavior doesn't make sense to me. Because when instead of building packed library I build an executable everything works perfectly. Why can't I build a packed library and make it work the same way. P.S. Packed library includes every dependency, same way as in executable. Any advice will be highly appreciated! Thank you in advance and happy new year! Kind Regards, Max
  13. I believe there is a misunderstanding and I am failing to explain correctly the issue that I am facing. Let me please try once again, if you still have patience. I prepared the following diagram: 1. TestStand Actor.exe is launched in LabVIEW Run-Time Server, hence the Messenger Library VIs will be loaded into memory. 2. TestStand Actor.exe runs the sequence file (with any kind of steps) using TestStand API. 3. Sequence File has some LabVIEW steps that are using Messenger Library VIs. LabVIEW Adapter in TestStand automatically uses the same LabVIEW Run-Time Engine Server as in step 1. Hence there will be a name conflict. Ideally I would build all of the LabVIEW steps into a packed library (as advised by NI). Doing that provides a namespace + puts all the dependencies into one file. However, this brakes communication in Messenger Library and steps become useless. Running steps without library produces a naming conflict in LabVIEW Run-Time Server.
  14. Unfortunately that didn't work. The same behavior appears as described in the initial post: "Send Message (without reply)" and "Receive Notification" work, however "Send Message (with reply)" doesn't. What I did was I created an .exe actor which receives and replies with a text message. Then I created a client actor that sends a message and waits for a reply. Source and Build for the client work perfectly. Then for a client actor I created a source distribution and included all dependencies in a library (that included Messenger Library). I also tried putting the client actor itself into a library, but still with no luck.
  15. Yes, you have a very good point here. Usually I follow this approach. However, TestStand Actor is allowed to load any sequence file through TestStand API. The sequence file itself sometimes calls LabVIEW code, which in my case by a coincidence use the same library that is already loaded by a Run-Time engine. For the sequence developer it is impossible to know that his steps will have a conflict in memory once deployed. Thank you for a suggestion about putting Actors and Messenger library under the library. It sounds like a potential solution, I will give it a go.
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