Could you please compile this as mex for windows 64 bit ? I can not run the compiler. Faster exp function with reduced accuracy.

Code for Exp function with reduced accuracy. I can not compile it.

Code from

https://www.mathworks.com/matlabcentral/newsreader/view_thread/173567

http://www-h.eng.cam.ac.uk/help/tpl/programs/Matlab/mex.html

#include <stddef.h>
#include <math.h>
#include "mex.h"

#ifndef mwSize
#define mwSize int
#endif

/* these 2 #define lines help make the later code more
readable */
/* Input Arguments */
#define PARAMETER_IN prhs[0]

/* Output Arguments */
#define RESULT_OUT plhs[0]

#define LITTLE_ENDIAN 1

static union
{
  double d;
  struct {
#ifdef LITTLE_ENDIAN
    int j,i;
#else
    int i,j;
#endif
  } n;
} _eco;

#define EXP_A (1048576/0.69314718055994530942)
#define EXP_C 60801
#define EXP(y) (_eco.n.i = EXP_A*(y) + (1072693248 - EXP_C), _eco.d)

void mexexp(double*y, double*yp, mwSize m) {
  while(m--) {
    *yp++ = EXP(*y++);
  }
}

void mexFunction( int nlhs, mxArray *plhs[],
                  int nrhs, const mxArray*prhs[] )
{
    mwSize numel;
    mwSize ndim;
    mwSize *dims;

        /* Check for proper number of arguments */
        if (nrhs != 1) {
            mexErrMsgTxt("One input argument required.");
        } else if (nlhs > 1) {
            mexErrMsgTxt("Too many output arguments.");
        } else if ( !mxIsDouble(PARAMETER_IN) ) {
            mexErrMsgTxt("Input must be double.");
        } else if ( mxIsComplex(PARAMETER_IN) ) {
            mexErrMsgTxt("Input cannot be complex.");
        }

        ndim = mxGetNumberOfDimensions(PARAMETER_IN);
        dims = mxGetDimensions(PARAMETER_IN);
        numel = mxGetNumberOfElements(PARAMETER_IN);

        /* Create a matrix for the return argument */
        RESULT_OUT = mxCreateNumericArray(ndim, dims,
    mxDOUBLE_CLASS, mxREAL);

        /* Do the actual computation*/
        mexexp(mxGetPr(PARAMETER_IN),mxGetPr(RESULT_OUT),numel);
        return;
    }

[Geoff Hayes]

Ole - why can't you build/compile this function with MEX? What errors are you observing?

[Jan]

I've removed a line break from the #define EXP line.

[Ole]

>> mex -setup Error using mex No supported compiler or SDK was found. For options, visit http://www.mathworks.com/support/compilers/R2015a/win64.html.

I can not install SDK for some reason.

>> gcc -o fastexp fastexp.c -lm Undefined function or variable 'gcc'.

[Jan]

GCC is a compiler under Linux. Before you can activate the compiler from the SDK for Windows, you have to download and install the SDK at first. Did you follow the instructions at http://www.mathworks.com/support/compilers/R2015a/win64.html carefully?

Answer 1

[Jan]

Here is a compiled version: RoughExp.mex

You might need the MSVC 2010 runtime libs, if you did not install them before: http://www.microsoft.com/en-us/download/details.aspx?id=14632

[Ole]

Thanks.