help with Compiling a mex-file

hello Folks,

I downloaded a Matlab package for probabilistic modeling of circular data with mixtures of von Mises distributions.

please see this link

https://github.com/chrschy/mvmdist?fbclid=IwAR1xY51kNpc6aYDoJ8GYAXkPC-A3tK6YvrKXwsi4-yudDq32OykR7IFOfq4

in the installation phase i have to do this :

1. Clone or download this repository and add it to your MATLAB search path.
2. Compile the *.mex-file located at @VonMisesMixture/private by browsing to that directory in MATLAB and running mex sampleVonMisesMex.c from the command line.

i didn't understand how to do the second step if any one can help

Answer 1

[Walter Roberson]

cd to the directory that you downloaded the code into.

Give the command

mex sampleVonMisesMex.c

If the compiling works then the routine should be ready to use, callable under the name sampleVonMisesMex

Before doing all of this you need to have installed a support compiler for your operating system and release, and have given the command

mex -setup c

and chosen a compiler if more than one is offered.

Answer 2

[Abdelmalek Benaimeur]

i got this error

>> mex sampleVonMisesMex.c
Building with 'MinGW64 Compiler (C)'.
C:\Program Files\MATLAB\R2018b\bin\mvmdist-master\@VonMisesMixture\private\sampleVonMisesMex.c: In function 'sample':
C:\Program Files\MATLAB\R2018b\bin\mvmdist-master\@VonMisesMixture\private\sampleVonMisesMex.c:54:32: warning: implicit declaration of function 'random' [-Wimplicit-function-declaration]
  srand( time(NULL) + clock() + random() );
                                ^~~~~~

Error using mex
C:\Users\mbenm\AppData\Local\Temp\mex_10616001118706_3404\sampleVonMisesMex.obj:sampleVonMisesMex.c:(.text+0x65):
undefined reference to `random'
collect2.exe: error: ld returned 1 exit status
 

would you please tell me what to do ?

[Walter Roberson]

Hmmm, I do not know where they are expecting to get random() from. random() is not part of the C language standard. C++ has a header named "<random>" but none of the functions are named random()

Answer 3

[Abdelmalek Benaimeur]

so what to do? any suggestions?

[Walter Roberson]

File a bug report with the author.

[Walter Roberson]

I checked further. It turns out that random() is part of POSIX stdlib.h but not part of any ISO C stdlib.h up to and including C18 .

http://man7.org/linux/man-pages/man3/random.3.html

Therefore the code is valid on POSIX compliant systems, and might be valid on some Unix systems that are not POSIX certified, but is potentially not valid on MS Windows.

[Juha Kuortti]

A little late, but you can also just modify the code in sampleVonMisesMex.c line 54:

srand( time(NULL) + clock() + random() );

to

srand( time(NULL) + clock());

This code initialises the random number generator ( function rand() later in the code) with only current time. In practice this should be sufficient, but for critical work you should consider something not temporally monotonic.

[Richard Cui]

Modify random() to rand(), which will do the work.

[Walter Roberson]

time() returns a time_t (data type not specified by C standard, but often some form of integer)

clock() returns a clock_t (data type not specified by C standard, but often some form of integer)

random() returns an int (not a long int)

The sum of those three is not well defined in type.

srand() requires an unsigned int parameter.

It is not obvious that adding those three types gives an appropriate parameter for srand()