This repository contains example programs for the use of mex files in Matlab on Linux and Mac OS X. I'm computing Fibonacci numbers in Matlab, Fortran, and C++. All of this works with GCC and Intel compilers.

• Edit fortran.makefile and make sure that MDIR points to your Matlab installation
• The default compiler is gfortran. If you want to use Intel's ifort, uncomment the appropriate lines in fortran.makefile
• Compile the mex file using make -f fortran.makefile

• Edit cpp.makefile and make sure that MDIR points to your Matlab installation
• The default compiler is g++ (gcc or clang depending on your system). If you want to use Intel's icpc, uncomment the appropriate lines in cpp.makefile
• Compile the mex file using make -f cpp.makefile

Run main.m in Matlab:

% use matlab (correct answer is 75025)
tic
fibonacci(25)
toc

% use Fortran
tic
gatewayFortran(25)
toc

% use C++
tic
gatewayCpp(25)
toc

Next, consider the different implementations of the Fibonacci function. Note that this is only meant as an illustration. There are much better ways to compute the Fibonacci numbers than the algorithm I'm using here.

The function fibonacci calls a Matlab implementation of the Fibonacci function:

function [ fnum ] = fibonacci( n )
  if (n<2)
    fnum = n;
  else
    fnum = fibonacci(n-1) + fibonacci(n-2);
  end
end

The function gatewayFortran calls the mex file that is implemented in Fortran. The underlying Fortran function is very simple:

recursive function fib (n)  result (fnum) 
  integer, intent(in)  :: n
  integer :: fnum
  if (n<2) then 
     fnum = n
  else
     fnum = fib(n-1) + fib(n-2)
  endif
end function fib

The function gatewayCpp calls the mex file that is implemented in C++. The underlying C++ function is very simple:

int fib(const int n) {
  int fnum;
  if (n<2) {
     fnum = n;
  } else {
     fnum = fib(n-1) + fib(n-2);
  }
  return fnum;
}

Average time in seconds to compute the 25th Fibonacci number (=75025) on different platforms using the GCC compilers:

I'm keeping the Fortran and C++ code self-contained. I'm also providing standalone programs ./standalone.f90.out and ./standalone.cpp.out that can be used to debug the Fortran and C++ code independently from Matlab. Travis CI is only building these standalone programs.

• /c++ - fibonacci.cpp Fibonacci function - fibonacci.h header file for Fibonacci function - gatewayCpp.cpp gateway script that can be called from Matlab - standalone.cpp a standalone program that calls the Fibonacci function independently from Matlab
• /fortran - fibonacci.f90 module with Fibonacci function - gatewayFortran.f90 gateway script that can be called from Matlab - globaldef.f90 module with global definitions - standalone.f90 a standalone program that calls the Fibonacci function independently from Matlab
• cpp.makefile C++ makefile for Linux and Mac OS X
• fibonacci.m Matlab implementation of the Fibonacci function
• fortran.makefile Fortran makefile for Linux and Mac OS X
• main.m Matlab script that calls both the Matlab and Fortran implementation