MATLAB: Mex function linking to BLAS

blaslapackmexfunction

hi gurus, i want to link a C mexfunction to the matlab version of BLAS, libmwblas, and also to lapack. where can i find the appropriate signatures (integer types, etc.) required to call the various routines? thanks in advance.

-dh

Best Answer

Hi,

take a look at the blas.h and lapack.h files in the extern\include subfolder of your MATLAB installation.

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MATLAB: Building Mex file with Fortan

Your main problem is that you need to create the output array PLHS(1) before you access it. Also your NLHS and NRHS types are wrong. Try this:

#include <fintrf.h>
C
C Gateway routine
C
    SUBROUTINE MEXFUNCTION(NLHS, PLHS, NRHS, PRHS)
    implicit none
C mexFunction arguments:
    MWPOINTER PLHS(*), PRHS(*)
    INTEGER NLHS, NRHS
    mwPointer, external :: mxGetPr, mxGetPi
    mwPointer, external :: mxCreateDoubleMatrix, mxCreateNumericArray
    mwSize, external :: mxGetM, mxGetN
    MWPOINTER YPP 
    mwSize M, N
    integer*4 ComplexFlag
    REAL *8 RYPP(1)
    RYPP(1) = 10
    M = 1
    N = 1
    ComplexFlag = 0
    PLHS(1) = mxCreateDoubleMatrix( M, N, ComplexFlag )
    YPP = MXGETPR(PLHS(1))
    CALL MXCOPYREAL8TOPTR(RYPP, YPP, M*N)
    RETURN
    END

MATLAB: Problem using BLAS routine ztbsv.c

All of the BLAS and LAPACK complex storage is based on an original Fortran standard, which has real and imaginary parts interleaved. The C structure doublecomplex is intended to mimic this storage scheme, and the blas.h header file should as well. Early versions of MATLAB did not have correct headers for the complex arguments of BLAS/LAPACK functions. I think that has been corrected but have not actually checked lately.

Your example doesn't make sense, and I assume it is a typo. This:

1+2i
2+3i
4+6i

Should be stored in memory as:

 {1,2,2,3,4,6}

Which is not what you have written.

I think you will need to post your complex code so we can look at it. Do you have both Ar and br as doublecomplex storage memory? I would also look at the blas.h and lapack.h header files for your version of MATLAB to see if they are as expected (possibly could be incorrect as noted above). There is always the chance that the library function itself has bugs in it, but I wouldn't assume that without checking everything else first. You could also download a C source code for ztbsv and call that routine (i.e., bypass the library function) to see if things work properly.

Best Answer

Related Solutions

MATLAB: Building Mex file with Fortan

MATLAB: Problem using BLAS routine ztbsv.c

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