In my team, we are using a high-performance C++ program to read data from the network. We want to place such data in a shared memory buffer in our C++ process for reading in a separate Matlab process that will further asynchronously process the data and provide a display interface.
All this is running on Windows.
What of the many cross-language mechanisms in Matlab is best suited to this purpose?
Thanks!
The best strategy is to use a memory-mapped file to provide data from one component and parse it from another. It appears Matlab's locking primitives are somewhat primitive, but fully worked out examples are on the Matworks website, including a simple chat application passing data between two Matlab instances.
I am trying to determine which of these two to buy for my work. I have used SIMULINK but not LabVIEW. Is there anyone who has used both and would like to provide some details? My investigation criteria are the user friendliness, availability of libraries and template functions, real-time probing facility, COTS hardware interfacing opportunity, quality of code generation, design for testability (i.e. ease of generating unit/acceptance tests), etc. However, if anyone would like to educate me with more criteria, please do so by all means!
For anyone who does not know about SIMULINK and LabVIEW - These are both Domain-Specific Languages (DSLs) intended for graphical dataflow modelling (and also code generation). These are multi-industrial tools and quite heavily used for engineering design and modelling.
IMPORTANT - I am quite interested to know if SIMULINK and LabVIEW offer real-time probing. For example, I have a model that I want to simulate. If there are variables associated to certain building blocks in that model, could I view them changing as the simulation continues? I know that it is certainly not possible with SIMULINK as it has a step-by-step debugger. I am not aware of anything similar in LabVIEW.
I really have not used LabVIEW and cannot obtain it temporarily as my work internet has got download restrictions and administrative privilege issues. This is the reason why I simply cannot use only NI website to draw conclusions. If there is any white paper available that addresses this issue, I would also love to know :)
UPDATE SINCE LAST POST
I have used MATLAB code generator and will not say that it is the best. However, I hear now that SIMULINK Embedded Coder is the best code generator and almost one of its own kind. Can anyone confirm whether or not this is good for safety critical system design i.e. generating code from safety-critical subsystem models. I know that the Mathworks is constantly trying to close the gap to achieve fully-flexible production-level C/C++ code generation.
I know that an ideal answer would be,"Depending on what you are trying to do, use a bit of both". And interestingly, I think I am heading to that direction. ATEOTD, it is a lot of money and need to be spent "nicely".
Thanks in advance.
I used labVIEW from 1995, and Simulink from 2000. Now I am involved in control system design, and simulation of robotic systems using labVIEW Real Time and automotive ECUs using MATALAB/Simulink/DSPACE .
LabVIEW is focus on measurement systems, and MATLAB/SIMULINK in dynamic simulation, so,
If you run complex simulations, and your work is create/debug complex simulation models of controllers or plants, use Simulink+RealTimeWorkShop+StateFlowChart. LabVIEW has no eficient code generators for dynamic simulation. RTW generates smaller and fastest code.
If your main work is developing systems with controllers and GUI for machines, or you want to deploy the controllers on field, use labVIEW.
If your main work is developing flexible HIL or SIL systems, with a good GUI, you can use VeriStand. Veristand can mix Simulink and LabVIEW code.
And if you have a big budget ( VERY BIG ) and you are working in automotive control prototypes, DSPACE hardware is a very good choice for fast development of automotive ECUS, or OPAL to develope electric power circuits. But only for prototype or HIL testing of controllers.
From the point of view of COTS hardware:
Mathworks don´t manufacture hardware -> Matlab/Simulink support hardware from several vendors.
National Instruments produce/sell hardware->LabVIEW Real Time is focused in support NationalInstruments hardware. There are no COTS full replacement.
I have absolutely no experience with Simulink, so I'll comment only on LV, although a quick read about Simulink on Wikipedia seems to indicate that it's focused mainly on simulation and modelling, which is certainly not the case with LabVIEW.
OK, so first of all, LV is NOT a DSL. While you wouldn't want to use it for any project, it's a general purpose programming language and you should take that into account. I know that NI has a simulation toolkit for LV, which might help you if that's what you're after, but I have absolutely no experience with it. The images I saw of it seemed to indicate that it adds a special kind of diagram to LV for simulation.
Second, LV is not restricted to any kind of hardware. It's a general purpose language, so you can write code which won't use any hardware at all, code which will use or run on NI's hardware or code which will use any hardware (be it through DLL calls, .NET assemblies, RS232, TCP, GPIB or any other option you can think of). There is quite a large collection of LV drivers for various devices and the quality of the driver usually depends on who wrote it.
Third, you can certainly probe in real time in LV. You write your code, just as you would in C or Java, and when you run it, you have several debugging options:
Single stepping. This isn't actually all that common, partially because LV is parallel.
Execution highlighting. This runs the code in slow motion, while showing all the values in the various wires.
Probes, which show you the last value that each wire had, where wires fill the same function that variables do in text based languages. This updates in real time and I assume is what you want.
Retain wire values, which allows you to probe a wire even after data passed through it. This is similar to what you get in text based IDEs with variables. In LV you don't usually have it because wire values are transient, so the value is not kept around unless you explicitly ask for it.
Of course, since you're talking about code, you could also simply write the code to display the values to the screen on a graph or a numeric indicator or to log them to a file, so there should be no need for actual probing. You could also add analysis code, etc.
Fourth, you could try downloading and running LV in a fully functional evaluation mode. If I remember correctly, NI currently gives you 7 days and then 45 days if you register on their site. If you can't do that on a work computer, you could try at home. If your problem is only with downloading, you could try contacting your local NI office and asking them to send you a DVD.
Note that I don't really know anything about modelling and simulation, so I have no idea what kind of code you would actually have to write in order to do what you want. I assume that if NI has a special module for it, then it's not something that you can completely cover in regular code (at least not if you want the original notation), but I would say that if you could write the code that does what you want in C, there's no reason you shouldn't be able to write it in LV (assuming, of course, that you know how to write code in LV).
A lot of the best answer would have to depend on your ultimate design requirements. Are you developing a product? If so, in what stage of development are you? Or are you doing research?
I recently did a comparison just as you are doing. I know LV, but was wanting to move towards a more hardware-scalable option, since NI HW is very expensive in volume. That is, my company was wanting to move towards a product. What LV and NI HW give you is flexibility. You can change code very quickly compared to C. On the other hand, LV does not run on nearly as many different HW platforms as C. So I wanted to find an inexpensive platform that would work well for real-time control and data acquisition, such that if we wanted to sell a product for, say, $30k, our controller wouldn't be costing $15k of that. We ended up with Diamond Systems Linux SBC's. Interestingly, Simulink ended up using the most expensive hardware! It did have a lot of flexibility, and could generate code, as well as model plants and controllers. But then, LV can do that as well.
As Yair wrote, LV has plenty of good debugging tools. One of the more interesting tools that is not so well known is the Suspend when Called option for a SubVI. This allows you to play with the inputs and outputs of a SubVI as much as you want while execution is paused.
MATLAB and Simulink are the defacto standard for control system design and simulation. Simulink controller models can be used for offline simulation in conjunction with plant models, all the way to realtime implementation on embedded targets. It is a general simulation framework with extensive built-in libraries as well as a la carte special purpose libraries, and can be extended through creation of custom blocks (S-function blocks) in C and other languages. It includes the ability to display values in graphs, numeric displays, gages, etc. while a nonrealtime simulation is taking place. Realtime target support from The Mathworks includes x86 (xPC Target) and several embedded targets (MPC555, etc.), and there is 3rd party support for other targets. The aforementioned dSPACE provides complete prototyping controllers including support for their quite powerful hardware. xPC Target includes support for a plethora of COTS PC data acquisition cards. Realtime target support includes GUI elements such as graphs, numeric displays gages, etc.
As I understand it (I have never really used it in anger), LabView only supports NI hardware, and is more hardware-oriented. Simulink supports hardware from multiple vendors, be it for data acquisition, or real-time implementation, but it may require a bit more work for the user to interface to his or her own hardware (less plug & play than LabView). On the other hand, Simulink provides tools to support the whole model-based design process, from modelling & simulation, control design, verification & validation, code generation, hardware-in-the-loop, etc...
Disclaimer: I used to work for MathWorks.
You guys may really be interested in Control Design adn Simulation Module for LabVIEW. It does a lot of simulations and in the future may be competitive to Simulink. I'm not a control engineer but I use it sometimes for simple testing and I'm glad that I don't have to learn Simulink from the beginning to do some work since I'm familiar with LabVIEW philosophy.
I am using an Arduino to control a car and I want to make it autonomous by using a webcam to see the object I want and make the car move to this location. I need several things:
MATLAB code
Interface between MATLAB and Arduino
How do I connect between them (software, not hardware)
I need any tutorial to learn or any instructions to make my project. I see many people have done this before, but unfortunately they did not mention how to start these kind of projects.
This question is fairly broad, so I apologize in advance for my somewhat general response.
The easiest way to interface a webcam with MATLAB is to make use of the Image Acquisition Toolbox. This link provides documentation detailing how to do this.
There is a good chance that you'll also want to make use of the Image Processing toolbox in MATLAB to be able to process the acquired images to determine where to go. See this doc. Though, after you've determined more specifically how you plan to process these images, there are probably numerous algorithms that you could find online that would not explicitly require this toolbox.
As far as interfacing with Arduino is concerned, there is a support package from the MathWorks that allows you to interface MATLAB code and Simulink models with Arduino. See this link
The only other general suggestion that I have is to consider using Simulink for this project rather than MATLAB. I feel that the model based approach of Simulink is a much better fit when designing control systems.
I hope that this helps you get things started.
I am looking at linking a few applications together (all written in different languages like C#, C++, Python) and I am not sure how to go about it.
What I mean by linking? The system I am working on consists of small programs each responsible for a particular processing task. I need to be able to transfer a data set from one application to another easily (the data set in question is not huge, probably a few megabytes) and I also need some form of way to control the current state of the operation (This is where a client-server model rings a bell)
It seems like sockets or maybe SOAP would be a universal solution but just wanted to get some opinions as to what people think about this subject.
Comments/suggestions will be appreciated, thanks!
I personally take a liking towards ØMQ. It's a library that has a familiar BSD-sockets-like interface for passing messages, but you'll find it implements interesting patterns for distributing tasks.
It sounds like you want to arrange several processes in a pipeline. ØMQ allows you to do that using push and poll sockets. (And afterwards, you'll find it's even possible to scale up across multiple processes and machines with little effort.) Take a look at the guide to get started, and the zmq_socket(3) manpage specifically for how push and pull works.
Bindings are available for all the languages you mention.
As for the contents of the message, ØMQ doesn't concern itself with that, they are just blocks of raw data. You can use any format that suits you, such as JSON, or perhaps Protocol Buffers.
What I'm not sure about is the ‘controlling state’ you mention. Are you interested in, for example, cancelling a job halfway through?
For C# to C# you can use Windows Communication Foundation. You may be able to use it with Python and C++ as well.
You may also want to checkout named pipes.
I would think about moving to a model where you eliminate the issue by having centralized data that all of the applications look at. Keep "one source of the truth" so to speak.
Most outside software has trouble linking against C++ code, due to the name-mangling algorithm it uses for its symbols. For that reason, when interfacing with programs written in other languages, it is often best to declare wrappers to things as extern "C" or inside an extern "C" { block.
I need to be able to transfer a data set from one application to another easily (the data set in question is not huge, probably a few megabytes)
Use the file system.
and I also need some form of way to control the current state of the operation
Again, use the file system. A "current_state.json" file with a JSON serialized object is perfect for multiple languages to work with.
It seems like sockets or maybe SOAP would be a universal solution.
Perhaps. But it's overkill for this kind of thing. Your OS already has all the facilities you need. Just use the file system. It's very simple and very reliable.
There are many ways to do interprocess communication. As you said, sockets may be a universal solution. SOAP, i think, is somewhat an overkill. You may also use mailslots. I wrote C++ application using it a couple of years ago. Named pipes could be also a solution, but if you are coding on Windows, it may be difficult.
In my opinion:
Sockets
Mailslots
Are the best candidates.
i have two machines running MATLAB and i need to exchange information(numbers,images) between them,is there a way in MATLAB i can do it?
If you have Parallel Computing Toolbox and MATLAB Distributed Computing Server, you can use MPI-style programming to send data between the two MATLAB processes. You can use functions like labSend and labReceive to send and receive data.
There are several possibilities without any extra toolboxes, depending on your specific needs. Check the Matlab help about external interfaces for details. For high performance, mexing a custom C communication is probably your best option. Using shared files on a network storage would be an alternative that is easier to implement but less effective, especially if you need frequent communication.
for an example of socket programming in MATLAB using Java, see this related post
Adding some specifics to other answers, here's an example of using Java for sockets. multicore and MatlabMPI use the filesystem, so I believe if you have a shared network filesystem you could use them across machines. And here is an old implementation in C++.
We have direct experience only with multicore, which is the least like real socket communication out of the above, but it gets the job done for coarsely parallel jobs.