Intel® FPGA SDK for OpenCL™ Standard Edition: Best Practices Guide

ID 683176
Date 9/24/2018
Public
Document Table of Contents

2.4.1. Area Analysis by Source

The area analysis by source report shows an approximation how how each line of the source code affects area usage. In this view, the area information is displayed hierarchically.

OpenCL kernel example that includes four loops:

 1  // ND-Range kernel with unrolled loops
 2  __attribute ((reqd_work_group_size(1024,1,1)))
 3  kernel void t (global int * out, int N) {
 4    int i = get_global_id(0);
 5    int j = 1;
 6    for (int k = 0; k < 4; k++) {
 7      #pragma unroll
 8      for (int n = 0; n < 4; n++) {
 9        j += out[k+n];
10      }
11    }
12    out[i] = j;
13
14    int m = 0;
15    #pragma unroll 1
16    for (int k = 0; k < N; k++) {
17      m += out[k/3];
18    }
19    #pragma unroll
20    for (int k = 0; k < 6; k++) {
21      m += out[k];
22    }
23    #pragma unroll 2
24    for (int k = 0; k < 6; k++) {
25      m += out[k];
26    }
27    out[2] = m;
28  }

The area report below lists the area usage for the kernel system, board interface, and global interconnects. These elements are system-level IP and are dependent on the Custom or Reference Platform that your design targets. The kernel t is within the hierarchy of the kernel system and is where the source code begins. The report specifies all the variables declared within the source code under kernel t and sorts the remaining area information by line number.

Figure 24. Source View of an Example Area Report

In this example, for the code line for the code line j += out[k+n] (line 9), the calculates the estimated area usage based on the area required to perform the addition and to load data from global memory. For the code line out[i] = j (line 12), the offline compiler calculates the estimated area usage based on the area required to compute the pointer value and then store it back to global memory.

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