1. A systolic array for a 2D-FIR filter for image processing
Sebastian Siegel
ECE 734 

2. Outline Why Systolic Arrays (SA)? Design Issues Approach Solution
Result

3. Why Systolic Arrays? (1)
4-level nested do-loop:

4. Why Systolic Arrays? (2)
Sequential execution on one MAC requires too much time Example: image: 512x512, filter: 3x Million 10 Mhz = 0.23 s
Algorithm in nested do-loop structure  Single Assignment Format possible  Parallel execution possible
Systematic approach vs. “rocket science”

5. Design Issues
Recall:
Avoid multiple access to the same data by pipelining it
Minimize execution time and registers
Maximize Usage of Processing Elements (PEs)

6. Approach (1)
Steps:
Rewrite Algorithm in Single Assignment Format (SAF)
Draw and examine Dep. Graph (DG)
Map DG to SA by generating suitable solutions and chose an optimal one Problem: SA too big  partitioning  data reaccessed or cache needed

7. Approach (2)
Partitioning of the DG generates even more (and better) solutions:

8. Solution

9. Result Fully pipelined SA 100% PE utilization
SA can be partitioned with relatively small cache and 100% data reuse or without cache and high data reuse
PEs and their interconnections (# of registers per pipeline) independent of filter size
Low latency for the results
Constant I/O rate
Fast MATLAB® implementation