I attached the pure sequential version of my program.

In the file, I give how I compile, How I run and the result. Here C is 5 
time faster than OCaml

Many thanks to tell me why my OCaml code is so slow.

Regards,
Frédéric Gava

ps: note that in a more generic version of the C code (that is, do 
memcpy because the data could be of any size,  (for example, matrices of 
polynomials) the ocaml code is faster and faster than the C one :-) )