MATLAB: ****The mex file with a different prhs****

int32int64mexmwpointermwsizeprhs

Hi, I have a compiled mex file that gives rubbish results.
After some detective work, I realised that the computational subroutine worked fine and that the problem was with the prhs. Strangely, the prhs did not correspond to my input.
I think it has most probably got to do with the type (int32 or int64), although I'm can't be absolutely sure. Does anybody know why it happened?
>> mex Print.F
>> Print(1,3)
ans =
    4613937818241073152
-------------------------------------------------------------------------
#include "fintrf.h"
C======================================================================
#if 0
C     
C     add.F
C    .F file needs to be preprocessed to generate .for equivalent
C     
#endif
C     
C     add.f
C
C     Adds two integers
C   
C======================================================================
C     *Gateway routine*
      subroutine mexFunction(nlhs, plhs, nrhs, prhs)
C     *Declarations*
      implicit none
C     *mexFunction arguments:*
      mwPointer plhs(*), prhs(*)
      integer nlhs, nrhs
C     *Declare local variables for the mexfunction arguments*
      mwPointer a, b
      mwPointer c
      mwSize mrows, ncols
      mwSize size
      mwSize :: one = 1
      integer*4 classid
      integer*4 :: mxREAL = 0
      integer*4 mxIsInt64
C     *Declare the symbolic names and types of this function*
      integer mxIsNumeric
      integer*4 mxClassIDFromClassName
      mwPointer mxGetNumberOfElements
      mwPointer mxCreateNumericMatrix
      mwPointer mxGetData, mxGetPr, mxCreateDoubleMatrix
      mwSize mxGetM, mxGetN
C     *Verify MEX-File Input and Output Arguments*
      if( nrhs /= 2 .or. nlhs > 1 ) then
            call mexErrMsgTxt('Need 2 inputs and at most 1 output')
      endif
      if( mxGetNumberOfElements(prhs(1)) /= 1 .or.
     +      mxGetNumberOfElements(prhs(2)) /= 1 ) then
            call mexErrMsgTxt('Inputs must be scalar')
      endif
C     *Prepare in/out matrix:*
      classid = mxClassIDFromClassName("int64")
      plhs(1) = mxCreateNumericMatrix(one,one,classid,mxREAL)
      a = mxGetPr(prhs(1))
      b = mxGetPr(prhs(2))
      c = mxGetPr(plhs(1))
C     *Get the size of the input array.*
c      mrows = mxGetM(prhs(1))
c      ncols = mxGetN(prhs(1))
c      size = mrows*ncols
C     *Call the computational subroutine.*
      call add(%val(a), %val(b), %val(c))
        return
        end
C-----------------------------------------------------------------------
C     *Computational subroutine*
        subroutine add(a, b, c)
        integer*8 a, b, c
        c = b
        return
        end

Best Answer

Hi,
it's not the data into the mex function (they are of type double, that's fine), but it's the plhs you have wrong: you create a numeric matrix of type int64, therefore you can't use mxGetPr but need to use mxGetData. And if you want to call your function with int64 you need to do explicitly, i.e.
Print(int64(1), int64(3))
Titus
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