If i understand correct, for equation 2, as i understand , if the lelf array y(k+i) etc and right array y(k) ete ready, then it is dot product, right?
MKL has such function , please see all mkl function list in https://software.intel.com/en-us/mkl-developer-reference-c
No direct for equation 3. But seems there are much optimize chance for the equation by manual code and several mkl dotproduct matrix vector functions. .