Simple mex question: how to call a mex function in matlab utilizing variables defined in matlab

19 views (last 30 days)
Nicholas on 14 Jul 2014
Answered: Jan on 15 Jul 2014
So I'm trying to convert pieces of a matlab program into mex files to increase the execution speed. The program has about 20 different matlab scripts in it. I'm relatively new to both c and matlab, how do I integrate the mex files into matlab? As an example, how do I rewrite this struct from .m to c to compile as mex to be used in the program?
function [local] = LocalInfo(Euler, k, q, qh, forcing)
% Extract local info for element k
% local struct
local = [];
local.force = feval(forcing, Euler, Euler.x(:,k));
local.q = squeeze(q(:,k,:));
local.q0 = squeeze(Euler.q0(:,k,:));
local.nx = Euler.nx(:,k);% normal vector
local.J = Euler.J(1,k);
local.rx = Euler.rx(1,k);
local.qh = reshape(qh(k:k+1,:),[],1);
local.k = k;

Fred Smith on 14 Jul 2014
MEX-functions can be called from MATLAB by name like any other MATLAB function. If you have foo.mexw64, you call it using regular function syntax from within MATLAB: foo(3,4). If both foo.m and foo.mexw64 exist, then foo(3,4) in MATLAB will invoke foo.mexw64 preferentially. This simple mechanism can be used to replace a MATLAB function with a MEX-function.
MEX functions can be created by hand from C or FORTRAN code using the "MEX" command. Your C or FORTRAN code will have to conform the the MEX-function API.
Alternatively, you can use MATLAB Coder to automatically convert your MATLAB code into C code, and wrap it up as a MEX-function. MATLAB Coder can handle many, but not all MATLAB constructs. The amount of acceleration you get will heavily depend on your application.

Jan on 15 Jul 2014
This piece of code is processed efficiently in Matlab. If you call a mex-function, which calls Matlab again for the feval, a lot of time is spend in the overheads of the interfaces. Therefore I'm convinced that this piece of code is faster, when you leave it in Matlab.

Mukul Rao on 14 Jul 2014
Hi,
MEX files are used to run C/C++ or Fortran codes in the MATLAB environment. This means that if you have an existing C code that you would like to execute in the MATLAB environment, you would have to first convert it to a MEX file by making certain changes, described in detail in the links below:
I assume that you have a few MATLAB scripts that you would like to run as a C application? In that case what would work best for you is the MATLAB Compiler toolbox. MATLAB Compiler can convert MATLAB code into a standalone executable or C/C++ shared libraries. Please refer the following link to get introduced to the MATLAB compiler:

Categories

Find more on Troubleshooting in MATLAB Compiler SDK in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!