something about codes

[leeeexp]

hello dgschwend:
typedef ap_uint<23> memaddr_t; // must remain <= 23 bits to fit into float
why must remain <= 23 bits to fit into float?
can I USE typedef ap_uint<32> memaddr_t;

[dgschwend]

Hi! Yes I think that‘s just a stale comment. Give it a try! ;)
Background: Initially, the idea was to copy also the layer configuration to the FPGA (shared mem), and have the entire network executed on the FPGA independent of the CPU. However, the FPGA memory port (SHARED_DRAM) can only have one data type in HLS, in this case float32. In order to read integers such as memory offsets (= memaddr_t), I would simply cast the float back to integer. Because re-interpretation casts are also not supported in HLS, I would need to do a normal cast. Because the float-mantissa is 23 bits, integers with <= 23 bits can be perfectly converted.