Which OpenCL APIs load kernels to FPGA?

OK, thanks. I am starting to understand.

Is there a place to read about the compiler/optimizer policy ? i.e. how many threads of each kernel are programmed in each work-group, when it knows the reqd_work_group_size() or not, and if there are enough resources on the fpga whether it adds some work-groups of each kernel although it does not have information about that, and so on .

Is there a way to know the resulted internal structure after the compilation ? or some summary.

Where can I find explanation on how to read the resulted compiler log ?