1. Optimizing stencil code for FPGA
Yang Liu

2. Overall Motivation
Accelerate Stencil code on both software and hardware level.
Software optimization: Algorithm level optimization
Hardware optimization: Data transfer rate, parallelism, and a specially designed memory controller

3. Executive summary
This project is intended to optimize stencil code performance on FPGA using OpenCL framework.

4. SDAccel
Xilinx’s design acceleration tool enable faster development and better performance
Supports standard OpenCL API to abstract hardware performance and optimize code to hardware
Available on AWS cloud

5. SDAccel Design Flow

6. Stencil Algorithm Application
Computer Fluid Simulation
Partial Differential equation
Many more..

7. Stencil Algorithm
Depend on nearest neighbor 2D 1D

8. Why we need to improve

9. Current Progress 1-D, 2-D implementation of stencil code is completed.
Optimization of 1-D, 2-D is half-way though.
Will be able to meet the goal of my proposal.

10. System Design: Data
Data set consists of 4096 bits random generated data.
Generated using C random function

11. System Design: Program
The stencil program is handwritten.
Then OpenCl configuration code are based on Xilinx Sdaccel Example

12. Loop Unrolling
out[i] = ALPHA * in1[i - 1] + in1[i + 1] + BETA * in1[i];
Vout_buffer[j] = ALPHA ^2 *(in1[j - 2] + v1_buffer[j + 2] + 2 * v1_buffer[j]) +
BETA * ALPHA^2 * v1_buffer[j + 1] * v1_buffer[j - 1] + v1_buffer[j];

13. Loop unrolling problem
Unused data at boundary will be larger.
Compute Data Area
Original
Compute Data Area
Unroll three times 3

14. Buffering
Data movement between host and board have a very high leniency
Resolution: Local buffer store part of the data
Host
4096
Board
Original
Optimized
1024

15. Multiple instance
Why just one, when we can have plenty?

16. System Test: Platform Based on Xilinx FPGA Local test KCU1500
Future test environment AWS F1 instance(VU9P)

17. Results: 1-D VS 1-D Optimized (Stencil Only)

18. Results: 2-D VS 2-D Optimized (Stencil only)

19. Results: 1-D VS 1-D Optimized (With Transfer)