Re: [Gnumex-users] GNUMEX-Help

[Kristján J. <jon...@hi...>]

Dear Hannes,

I believe gnumex is completely outdated by now. I have been using mex out of the box with Matlab recently on my Mac with no problems, connecting with C and then calling Fortran from C. I would use gfortran with the switch -std=legacy. I would also use a C gateway function to connect between Matlab and Fortran. I don’t know much about what would happen on a Windows machine, but note that Matlab now claims to support<https://www.mathworks.com/support/requirements/supported-compilers.html> MinGW 6.3 C/C++.

Depending on your C knowledge the effort could range from easy to difficult.

Here is a simple example:

#include "mex.h"
// xy = prod_gw(x,y) calls prod.f do compute the scalar product dot(x,y)
// Returns silently with xy = 0 if not called with 2 arguments or if x and y
// have different lengths. Other errors are not caught.

void prod_(double x[], double y[], double *xy, int *n);

void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) {
  double *xy, *x, *y;
  int n;
  plhs[0] = mxCreateDoubleMatrix(1, 1, mxREAL);
  xy = mxGetPr(plhs[0]);
  *xy = 0;
  if (nrhs != 2) return;
  n = mxGetNumberOfElements(prhs[0]);
  if (n != mxGetNumberOfElements(prhs[0])) return;
  x = mxGetPr(prhs[0]);
  y = mxGetPr(prhs[1]);
  *xy = 30;
  prod_(x, y, xy, &n);
}

I could then have a compile-link script:

function mexprod()
  !/usr/local/bin/gfortran -c -std=legacy prod.f
  mex prod_gw.c prod.o
end

and compile and run with:

mexprod
prod_gw([1 2], [3 4])
ans =
    11

With the newest Matlab you could also use mxGetDoubles instead of mxGetPr and mex with

mex -R2018a prod_gw.c prod.o

(with no complex numbers you get the same results)

Með kveðju/regards, Kristján

Kristján Jónasson
prófessor
Námsbraut í tölvunarfræði / Department of Computer Science
Verkfræði- og náttúruvísindasvið / School of Engineering and Natural Sciences
Háskóli Íslands / University of Iceland
Herb. 211, Tæknigarður, Dunhaga 5, Reykjavík
jon...@hi...<mailto:jon...@hi...>, http://notendur.hi.is/jonasson
+354-5254735, +354-8228860 (mobile)


On 19 Aug 2019, at 14:07, Hannes Rox <han...@tu...<mailto:han...@tu...>> wrote:

Dear Mr. Jonasson and Mr. Nicholson,

First of all, I would like to thank you for providing gnumex for free and with a very detailed documentation. Unfortunately, I still have problems using it, so I would like to ask you if you can help me or give me some advice.

For my studies I have to use a code in Fortran 77 using the mex function in Matlab. I have everything installed as described in the documentation. I also tried it with the 32- and 64-bit version of MinGW. However, again and again I get error/warning messages.


When running Gnumex.m, the warning comes after confirming "Make options file":


Can not correct mex.pl - readme file in gnumex folder.

I can't fix this, because this file doesn't exist on my PC (I can't find a file named"mex.pl" anywhere). If I ignore the warning and create the "options file" then comes following warning in the Command Window of Matlab:

Warning: Could not copy the created mexopts.stp file to the directory:
C:\Program Files\MATLAB\R2018b\bin\win64\mexopts
This only means that commands such as mex.getCompilerConfigurations will not work. It does not affect
the ability to compile mex or other files. To fix this problem you must copy the contents of the file
C:\Users\hanne\AppData\Roaming\MathWorks\MATLAB\R2018b\mexopts.stp
to the file
C:\Program Files\MATLAB\R2018b\bin\win64\mexopts\GNUMEXOPTS.stp
The copyfile funtion reported the following error when it attempted this:
Zugriff verweigert

I have fixed this as indicated. However, if I use now the mex function in Matlab, this error message appears:

Error using mex
No supported compiler was found. For options, visit https://www.mathworks.com/support/compilers.

So it doesn't work and since the Fortran code to be used is relatively complex and long, it is unfortunately very time-consuming to transform the code into Matlab. That's why it would help me a lot if I can do this with Gnumex. If this is helpful for a possible fix, here are some facts about my system:

Matlab-Version: R2018b
Windows 10 (64 bit)
Intel Core i7-7500
If you need further information or have any questions, I am glad to answer them.

Yours sincerely
Hannes Rox