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

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

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

Why Systolic Arrays? (2) Sequential execution on one MAC requires too much time Example: image: 512x512, filter: 3x3 2.3 Million operations @ 10 Mhz = 0.23 s Algorithm in nested do-loop structure  Single Assignment Format possible  Parallel execution possible Systematic approach vs. “rocket science”

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

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

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

Solution

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