In this example a kernel matrix is computed for a given string data set. The
CommUlongString kernel is used to compute the spectrum kernel from strings that
have been mapped into unsigned 64bit integers. These 64bit integers correspond
to k-mers. To be applicable in this kernel the mapped k-mers have to be sorted.
This is done using the SortUlongString preprocessor, which sorts the indivual
strings in ascending order. The kernel function basically uses the algorithm in
the unix "comm" command (hence the name). Note that this representation enables
spectrum kernels of order 8 for 8bit alphabets (like binaries) and order 32 for
2-bit alphabets like DNA. For this kernel the linadd speedups are implemented
(though there is room for improvement here when a whole set of sequences is
ADDed) using sorted lists.
