Buffer Location Constraints - 2025.2 English - UG1603

The AI Engine-ML compiler tries to automatically allocate buffers for buffers, lookup tables, and runtime parameters in the most efficient manner possible. However, you might want to explicitly control their placement in memory. Similar to the kernels shown previously in this section, buffers inferred on a kernel port can also use location constraints. You can map them to specific tiles, banks, or address offsets. The following example illustrates this.

#include <adf.h>
#include "kernels.h"
#define NUMCORES (COLS*ROWS) 

template <int COLS, int ROWS, int STARTCOL, int STARTROW>
class indep_nodes_graph2 : public adf::graph {
 public:
   adf::kernel kr[NUMCORES];
   adf::port<input> datain[NUMCORES] ;
   adf::port<output> dataout[NUMCORES] ;
  
 indep_nodes_graph() {
  for (int i = 0; i < COLS; i++) {
    for (int j = 0; j < ROWS; j++) {
      int k = i*ROWS + j;
      kr[k] = adf::kernel::create(mykernel);
      adf::source(kr[k])  = "kernels/kernel.cc";
      adf::runtime<ratio>(kr[k]) = 0.9;
      adf::location<adf::kernel>(kr[k]) = adf::tile(STARTCOL+i, STARTROW+j); // kernel location
      adf::location<adf::buffer>(kr[k].in[0]) = 
        { adf::address(STARTCOL+i, STARTROW+j, 0x0), 
          adf::address(STARTCOL+i, STARTROW+j, 0x2000) };          // double buffer location
      adf::location<adf::stack>(kr[k]) = adf::bank(STARTCOL+i, STARTROW+j, 2); // stack location
      adf::location<adf::buffer>(kr[k].out[0]) = adf::location<adf::kernel>(kr[k]); // relative buffer location
    }
  }

  for (int i = 0; i < NUMCORES; i++) {
    adf::connect(datain[i], kr[i].in[0]);
    adf::connect(kr[i].out[0], dataout[i]);
  }
 };
};

In the previous code, the location of double buffers at port kr[k].in[0] is constrained to the specific memory tile address offsets that are created using the address(col,row,offset) constructor. Furthermore, the location of the system memory (including the sync buffer, stack and static heap) for the processor that executes kernel instance kr[k] is constrained to a particular bank using the bank(col,row,bankid) constructor. Finally, the tile location of the buffers connected to the port kr[k].out[0] is constrained to be the same tile as that of the kernel instance kr[k]. Buffer location constraints are applied on kernel buffer ports.

{
  "PortConstraints": {
    "gr.k[0].in[0]": {
      "buffers": [{
          "column": 16,
          "row": 1,
          "bankId": 0,
          "offset": 16320
        }, {
          "column": 16,
          "row": 1,
          "bankId": 3,
          "offset": 0
        }]
    }
  }
}

{
  "PortConstraints": {
    "gr.fir24.in[1]": {
      "buffers": [{
          "column": 17,
          "row": 1,
          "bankId": 0,
          "offset": 16320
        }, {
          "column": 17,
          "row": 1,
          "bankId": 3,
          "offset": 0
        }, {
          "column": 18,
          "row": 1,
          "bankId": 0,
          "offset": 16224
        }]
    }
  }
}