integer - Is there a way to determine the size of BLAS IDAMAX function? -

i determine size of integer function idamax in blas fortran library. can either 4-bytes (i32lp64 model) or 8-bytes (ilp64).

knowing size can determine overall integer declaration (integer*4 or integer*8) in prebuild blas library.

the problem sizeof(*idamax_(&n, dx,&incx)) of program below returning 4, though expect 8 mkl-integer*8 blas.

any comments, please ?

#include <stdio.h> void main() { extern * idamax_(); // external fortran blas function idamax int n=2; int incx=1; //long  n=2; long incx=1; double dx[2]; dx[0]=1.0; dx[1]=2.0; printf("sizeof(n)=%i\n",sizeof(n)); printf("sizeof(*idamax_(&n, dx, &incx))=%i\n",sizeof(*idamax_(&n, dx,&incx)) ); // still returns 4 !!! //printf("sizeof(idamax_(&n, dx, &incx))=%i\n",sizeof(idamax_(&n, dx, &incx)) ); // idamax call crashes wrong integer sizes - mkl, gnu ibblas.a ! same fortran idamax_(&n, dx, &incx); } 

your code not determining function in blas fortran library. it's determining function declared with

extern * idamax_(); 

as did not specify return type of function, it's default int, constant size of 4 on machines.

if want determine return type of mkl's blas function, thing need check header file. in ${mkl_root}/include/mkl_blas.h can find

mkl_int idamax(const mkl_int *n, const double *x, const mkl_int *incx); 

the return type mkl_int, , size sizeof(mkl_int), determined on compile time. can find similar in ${mkl_root}/include/mkl_types.h

#ifdef mkl_ilp64   #ifndef mkl_int     #define mkl_int mkl_int64   #endif #else   #ifndef mkl_int     #define mkl_int int   #endif #endif 

so size of mkl_int depends on whether define mkl_ilp64 or not @ compile time.