Matlab calling C function using mex - matlab

Question

First of all, I never tried to call C code in a Matlab program - so it might just be a stupid mistake which I just can't figure out.
The C function is the following one and can be found on here, it is called durlevML.c and is part of the ARFIMA(p,d,q) estimator suite:
#include "mex.h"
#include "matrix.h"
#define square(p) ((p)*(p))
#define inv(q) (1/(q))
/* Durbin-Levinson algorithm for linear stationary AR(FI)MA(p,d,q) processes
Slightly altered for the maximum likelihood estimation
(C) György Inzelt 2011 */
void levinson_recur1(double* v,double* L, int N, double* gammas,int step)
{
int i,k;
if(step==0)
{
*(v + step) = *(gammas + step);
*(L + step) = 1;
for(k = step+1;k < N;++k)
{
*(L + k) = 0;
}
}
else if(step > 0 && step < N)
{
//phi_tt
*(L + step*N ) = (-1.00)* *(gammas + step);
if(step > 1)
{
for(i = 1;i < step ;++i)
{
*(L + step*N) -= *(L + (step-1)*N + (step -1) - i ) * *(gammas + step - i) ;
}
}
*(L +step*N) *= inv( *(v + step-1) );
//v_t
*(v + step) = *(v + step-1)*(1- square( *(L + step*N) ));
//phi_tj
for(i =1; i < step; ++i)
{
*(L + step*N + step - i) = *(L + (step-1)*N + (step -1) - i) + *(L + step*N ) * *(L + (step-1)*N + i -1 ) ;
}
//filling L with zeros and ones
*(L + step*N + step ) = 1;
if(step != N-1)
{
for(k = step*N +step+1 ;k < step*N + N ;++k)
{
*(L + k) =0;
}
}
}
if(step < N-1)
levinson_recur1(v,L,N,gammas,++step);
}
/* The gateway function */
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
int step=0;
int N;
double *gammas,*v,*L;
// getting the autocovariances
gammas = mxGetPr(prhs[0]);
N = mxGetM(prhs[0]);
// v
plhs[0] = mxCreateDoubleMatrix(0,0,mxREAL);
mxSetM(plhs[0],N);
mxSetN(plhs[0],1);
mxSetData(plhs[0], mxMalloc(sizeof(double)*N*1));
// L
plhs[1] = mxCreateDoubleMatrix(0,0,mxREAL);
mxSetM(plhs[1],square(N));
mxSetN(plhs[1],1);
mxSetData(plhs[1], mxMalloc(sizeof(double)*square(N)*1));
//
v = mxGetPr(plhs[0]);
L = mxGetPr(plhs[1]);
//
levinson_recur1(v, L, N,gammas,step);
//
return;
}
I have two problems now, the first one I already solved:
I got the following warning
Warning: You are using gcc version "4.6.3-1ubuntu5)". The version
currently supported with MEX is "4.4.6".
For a list of currently supported compilers see:
http://www.mathworks.com/support/compilers/current_release/
mex: durlevML.c not a normal file or does not exist.
but following the solution by changing the corresponding entries and installing the gcc-4.4 the warning disappeared, but the second actual problem still persists, although I don't get any warning any longer I still get the error
mex: durlevML.c not a normal file or does not exist.
What can be the possible reason for this?
I am using
ubuntu 12.04
Matlab 2012b
gcc-4.6 but was able to bring Matlab to use gcc-4.4
The problem occurred while running the function arfima_test.m which calls the durlevML.c function, the relevant (I guess) part of this is
% compiling the C/MEX file
c = input('Would you like to compile the MEX source? (1/0)');
switch c
case(1)
mex durlevML.c
case(0)
end

Answer 1

My thanks go to Ander Biguri due to his the comment!
The solution was indeed very easy, the problem was that the C file durlevML.c was not properly linked, so the compiler couldn't find anything. So I had to add some information in arfima_test.m in the following way
mex durlevML.c <---------------- needs to be linked /home/....
The C code itself was alright with one smaller issue. My compiler - I used gcc-4.4 due to Matlab incompatibilities with newer ones - didn't recognize the comments // and always produced errors, so I had to change them to the long comment format /**/ which finally worked.
Besides this everything worked, as far as I can tell!