. A Brief History of MATLAB to C In April, 2011, MathWorks introduced MATLAB Coder as a stand-alone product to generate C code from MATLAB code. This tool lets user generate readable, portable, and customizable C code from their MATLAB algorithms. Many astute readers will notice that C code generation from MATLAB isn't really brand new - and that we've had this capability to generate C code from MATLAB for quite some time now. Yes, that's true - we've been incubating this technology for quite some time till we felt it was ready to debut as a stand alone tool. Here's a timeline of this technology over the past few years.
Static allocation with fixed maximum size: you can initialize variables to the maximum possible static size (like I did in the example above). In the generated code, memory is prealloacted to this size. Variable sizing with maximum size allocation: this option will declare the memory for the variable in the generated code to its maximum possible size, but you can dynamically grow or shrink the variable size within this allocated maximum. Variable sizing with dynamic memory allocation: this results in the generated code using malloc to allocate the memory for the variables that change in size during code execution. The last two options can be enabled by turning on the variable-sizing feature in the configuration parameters.
However, do remember that enabling this option also makes the resulting C code bigger in size - so if you can avoid it, you can get much more compact and possibly more efficient code. Use Cases of MATLAB Coder The primary use of MATLAB Coder is to enable algorithm developers and system engineers working in MATLAB to quickly generate readable and portable C code.
The generated C code can be used in different ways supporting different workflows. Here are a few use cases of MATLAB Coder. Create standalone executables from your algorithms for prototyping on a PC. Speed up your MATLAB algorithm code (or portions of it) by generating and executing the MEX functions.
Integrate your MATLAB algorithms as C source code or compiled library with your hand-written software I won't be talking about creating standalone executables or creating libraries from MATLAB Coder in this blog; I'll, however, say a few words on generating MEX functions. Generating MEX Functions for Simulation Acceleration The MEX interface enables you to integrate C code into MATLAB. One common use of MEX is to speed up performance bottlenecks in MATLAB code by re-writing them in C and executing them back in MATLAB as MEX functions. MATLAB Coder can save you time and effort by automatically generating MEX functions from your MATLAB code (and allowing you to import legacy C code easily as well). The speed-up you get through automatic MEX generation can vary quite a bit depending on the application. In some cases, you may not get any speed up at all, or possibly even a slow-down, as MATLAB language has gotten quite smart and efficient in computing many built-in functions by automatically taking advantage of processor specific routines (such as Intel Performance Primitives) and multithreading to utilize multiple cores. A few guidelines that you can use to determine if your algorithm is a good candidate for speed-up with MEX are.
C Code In Matlab
'If I want the resulting code to look different, can I just edit the generated code?' You can certainly edit the generated code; as you have just seen in the examples shown here, the code is very readable. However, once you modify it, you lose the connectivity to the original MATLAB code that generated it.
'How can I optimize the code, or customize its look and feel?' One easy way to modify the generated code is to change MATLAB Coder configuration parameters. Another way to customize the generated code is to directly edit the MATLAB code such as explicitly breaking up certain compact vector/matrix operations into for loops or other constructs you'd like to see in the generated code.
'What about incorporating hand-optimized or processor specific intrinsics for certain portions of the code?' Coder.ceval is a command in MATLAB Coder that let's you integrate custom C code into your MATLAB code for both simulation and code generation. Using this you can use hand-optimized or legacy C code in your algorithms. Embedded Coder is another product that adds many code optimization and customization capabilities to MATLAB Coder such as using code replacement technology to incorporate optimized C code. It also lets you to customize the look-and-feel of the code. Learning More About MATLAB Coder You can find more information about MATLAB Coder on the, which includes demos and recorded webinars. The is also an excellent resource to find answers to questions you might have when starting with this product.
Please feel free to share your thoughts and comments on topics discussed here in this posting. Published with MATLAB® 7.13. Oyster Engineer replied on: 3 of 9 A couple of comments. 1st, I don’t see any logic in the History you discuss. How is new capability in MatLab related in any way to the previous capability in Simulink? 2nd, You should have introduced MEX in more detail up front rather than at the end as a “by the way” method of using this new product’s capability.
Further, don’t users need a clear understanding of how to revise this autogenerated C code to re-use in MatLab? Where is this sound guidance? Frankly, one of the main advantages of MatLab is that I don’t have to be a master of C to write high performance technical computing software. 3rd, I think you’ve violated some sound Coding Style Guidelines by using style: notDone = 1. While notDone Rather than: Done = 0. Replied on: 4 of 9 Arvind, 1. As you point out, autogenerated mex files can be much slower than m-code.
Here’s an example:. However, Mike Hosea pointed out in that thread that one possibilit is to use eml.extrinsic (I assume there’s something similar in codegen) to use use the Matlab version of certain functions like FFT that may be better optimized than the eml (or codegen version). I just upgraded to R2011A and tried codegen to autogenerate a mex-file from an m-file.
Couldn’t do it because I don’t have a license for Coder. However, I could still use emlmex, though I was warned that emlmex is going away in future versions. Is emlmex synonymous with codegen when used for generating mex-files? That is does emlmex generate the same c-code that codegen does? When emlmex goes away, will base matlab come with a “codegen lite” that has the emlmex functionality? Arvind replied on: 5 of 9 Venn: We currently don’t support C templates; moreover, we don’t generate templates for many reasons. First of all C template semantics and dispatching rules are complex and would not be easy to build a tool that would reliably get this right.
Secondly, it would be hard to establish what parameters would be appropriate. Discovering how to generalize code for the purpose of creating templates is a hard problem that’d d require some sort of symbolic evaluation. Preprocessor directives really don’t help with this problem, unless you imagine recompiling the code with different header files. Even in this approach, discovering the parameters, as in the case of templates, is the challenge. Arvind replied on: 6 of 9 Oyster engineer: Re: “ don’t users need a clear understanding of how to revise this autogenerated C code to re-use in MatLab?” It’s not clear what you mean by “revise the autogenerated code”. If you are referring how to execute the generated code in MATLAB without manually creating a MEX wrapper, one option is to use the MEX generation capability in MATLAB Coder to automatically compile your MATLAB code directly into a MEX function.
Another approach is to use the coder.ceval function (also in MATLAB Coder), that lets you call not just the auto generated C code, but any legacy C code for simulation and code generation in your MATLAB code. Arvind replied on: 7 of 9 Hi Paul J: 1.
You could certainly try coder.extrinsic to call built-in/toolbox functions in your MATLAB code that are not supported for code generation. A more uncommon usage for coder.extrinsic is to keep the processing of certain (MATLAB Coder supported) built-in functions in MATLAB instead of generating code for them, especially if they are more efficient in MATLAB as is. But that begs the question, why you would even want to use MATLAB Coder instead of just staying in MATLAB. As I state in the article, if bulk of your processing is spent on such functions, you may be better off working within MATLAB to identify ways to speed up the rest of your code.
Default option for the codegen command is to generate MEX. The C code that is generated for MEX is a bit different from the codegen command when choosing to generate C source code. This is because, the code itself will look different when we auto-generate the MEX wrappers within the algorithm C code, but also introduce certain run-time and CTRL-C checking as the resulting MEX is intended for execution within MATLAB. You can certainly turn off some of these memory integrity checks and other options from the build settings. Emlmex is a legacy function that’s not supported any longer and this capability will be available only through codegen. Current versions of emlmex are being maintained in the product (and not documented) for backward compatibility for a limited period, and will be removed soon.
Going forward you would need a MATLAB Coder license to be able to generate MEX functions automatically. We may be considering a ‘codegen lite’ option but currently don’t have plans for releasing such a capability. Replied on: 8 of 9 Arvind, 1. In this case I was in the following situation. I had an m-file that I wanted to run from Matlab and also call from an embedded function in Simulink. The simulink model slowed to a crawl and as best I could determine the issue was that code generated for Simulink, which I assume is using the same engine as emlmex, was slowing down because it doesn’t use the same optimized version of FFT as Matlab does. So in this case it might have been better to specify eml.extrinsic(‘fft’) so that the Simulink code would use the optimized Matlab version.
I hope I explained it well. In the future, will Simulink still support embedded functions and Simulink Accelerator without an extra license for MATLAB Coder? I’m still a little hazy about the relationship between EML and Coder. Does the latter replace the former? Arvind replied on: 9 of 9 Paul: 1.
Thanks for the clarification. You could certainly try coder.extrinsic here to force execution of certain function back in MATLAB if they are faster there (like FFT).
Do keep in mind that the marshalling of data back and forth adds some overhead and in some cases could offset the speed advantages you may get by running in native MATLAB. MATLAB Coder replaces EML – but certain functionality such as the MATLAB Function block in Simulink that uses code generation technology in MATLAB will continue to work without a separate MATLAB Coder license in the foreseeable future.
The first thing you need to realise is that porting code from one language to another (especially languages as different as Matlab and C) is generally non-trivial and time-consuming. You need to know both languages well, and you need to have similar facilities available in both. In the case of Matlab and C, Matlab gives you a lot of stuff that you just won't have available in C without using libraries.
So the first thing to do is identify which libraries you're going to need to use in C. (You can write some of the stuff yourself, but you'll be there a long time if you write all of it yourself.) If you're doing image processing, I highly recommend looking into something like ITK at - I've written my image processing software twice in C, once without ITK (coding everything myself) and once with, and the version that used ITK was finished faster, performed better and was ten times more fun to work on. I also used the to convert some functions consisting of a few hundred lines of MATLAB into C. This included using MATLAB's eigenvalue solver and matrix inversion functions. Although Coder was able to produce C code (which theoretically was identical), it was very convoluted, bloated, impossible to decipher, and appeared to be extremely inefficient. It literally created about 10x as many lines of code as it should have needed. I ended up converting it all by hand so that I would actually be able to comprehend the C code later and make further changes/updates.
This task however, can be very tedious/dangerous, as the array indexing in Matlab is 1-based and in C it's 0-based. You're likely to add bugs into the code, as I experienced. You'll also have to convert any vector/matrix arithmetic into loops that handle scalars (or use some type of C matrix algebra package). Matlab has a tool called 'Matlab Coder' which can convert your matlab file to C code or mex file. My code is relatively simple so it works fine. Speed up gain is about 10 times faster. This saves me time coding a few hundreds lines.
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Hope it's helpful for you too The links describe the process of converting your code in 3 major steps:. First you need to make a few simplifications in your present code so that it would be simple enough for the Coder to translate. Second, you will use the tool to generate a mex file and test if everything is actually working. Finally you would change some setting and generate the C code. In my case, the C code has about 700 lines including all the original matlab code (about 150 lines) as comments. I think it's quite readable and could be improve upon. However, I already get a 10 times speed up gain from the mex file anyway.
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So this is definitely a good thing. We can't not be sure that this will work in all case but it's definitely worth trying. I remember there is a tool to export m-files as c()-files.
But I could never get that running. You need to add some obscure MATLAB-headers in the c/ccode. And I think it is also not recommended. If you have running MATLAB-code, it shouldn't take too much effort to do the conversion 'by hand'. I have been working on several project where MATLAB was used and it was never consider to use any tools to convert the code to C/C.
It was always done 'by hand'. I believe to have been the only one who ever investigate into using a tool.