Sorting a vector on FPGA device using dpc++

Hello,

I want to sort a vector using DPC++, but on an FPGA device in parallel. The merge sort example on reference designs for DPC++ FPGA is very complex and I can't seem to understand it. I would like to make my own merge sort, but I don't know how to merge the values in accessors for example and is it possible to use built-in functions like swap() and max() inside FPGA parallel_for?

Thank you!