Intel® oneAPI Math Kernel Library Developer Reference - C
Several aspects of the Intel® oneAPI Math Kernel Library RCI ISS interface are platform-specific and language-specific. To promote portability across platforms and ease of use across different languages, include one of the Intel® oneAPI Math Kernel Library RCI ISS language-specific header files.
Intel® oneAPI Math Kernel Library does not support the RCI ISS interface unless you include the language-specific header file.