Figure 2.

The grid represents 96 × 64 pixels in local memory (each square is one pixel). As 32 x 32 threads are used per thread block, each thread needs to read 6 values from global memory into local memory [(96 × 64)/(32 × 32) = 6]. A yellow halo needs to be loaded into local memory to be able to calculate all the filter responses. In this case 90 × 58 valid filter responses are calculated, making it possible to apply at most a filter of size 7 × 7. The 90 × 58 filter responses are calculated as 6 runs, the first 2 consisting of 32 × 32 pixels (marked light red and light blue). The 1024 filter responses (32 × 32) are calculated in parallel, and the gray squares represent three filter responses being calculated. Note that neighboring filter responses are calculated using mainly the same pixels. Three additional filter responses are calculated in blocks of 32 × 26 or 26 × 32 pixels (marked green, dark blue and dark red). Finally, a block of 26 × 26 pixels is processed (marked purple). The halo can easily be changed to handle larger filters.