Function igraph_blas_dgemv 

pub unsafe extern "C" fn igraph_blas_dgemv(
    transpose: igraph_bool_t,
    alpha: igraph_real_t,
    a: *const igraph_matrix_t,
    x: *const igraph_vector_t,
    beta: igraph_real_t,
    y: *mut igraph_vector_t,
) -> igraph_error_t

\section about_blas BLAS interface in igraph

BLAS is a highly optimized library for basic linear algebra operations such as vector-vector, matrix-vector and matrix-matrix product. Please see http://www.netlib.org/blas/ for details and a reference implementation in Fortran. igraph contains some wrapper functions that can be used to call BLAS routines in a somewhat more user-friendly way. Not all BLAS routines are included in igraph, and even those which are included might not have wrappers; the extension of the set of wrapped functions will probably be driven by igraph's internal requirements. The wrapper functions usually substitute double-precision floating point arrays used by BLAS with \type igraph_vector_t and \type igraph_matrix_t instances and also remove those parameters (such as the number of rows/columns) that can be inferred from the passed arguments directly.