DSP Algorithms for CBE Architecture Jan Kryl (krylj1@fel.cvut.cz) - - PowerPoint PPT Presentation

IBM ČVUT Stud ent Resea rch Project 2 006

DSP Algorithms for CBE Architecture

Jan Kryl

(krylj1@fel.cvut.cz)

Petr Kurtin

(kurtip1@fel.cvut.cz)

IBM ČVUT Student Research Project 2006 (2 z 14)

• Introduction to DSP Algorithms
• Overview of CBE Architecture
• Implementation

– DSP Library – JPEG Library

• Design issues
• Concluding notes

In this talk…

IBM ČVUT Student Research Project 2006 (3 z 14)

• Application fields

– Audio signal processing (mp3, vorbis compression) – Digital image (jpeg compression) – Digital video (closely related to digital image processing) – Communications, navigation, radar, GPS

• Signal representation

– Time, Spatial, Frequency, Autocorrelation or Wavelet domain

DSP Algorithms

IBM ČVUT Student Research Project 2006 (4 z 14)

• Domain transformation algorithms

– Discrete Cosine Transform (image and audio compression)

• Filter is essential unit in DSP

– FIR filters (no feedback) – IIR filters (feedback -> can be unstable)

• Frequency analysis

– Fourier transforms, resolution, spectral leakage and windowing

DSP Algorithms (cont.)

IBM ČVUT Student Research Project 2006 (5 z 14)

• In fact, it's not a single processor but one PPE and

eight SPEs

• PPE (Power Processor Element)

– 64-bit, general purpose, PowerPC compliant processor – Runs OS, manages SPEs

• SPE (Synergistic Processor Elements)

– SIMD coprocessor specialized for computation intensive tasks

Cell Processor

IBM ČVUT Student Research Project 2006 (6 z 14)

• PPE and SPEs are connected through high speed EIB

(Element Interconnect Bus)

• Developement

– Various kinds of libraries (math, game, audio, ...) – Runs Linux – Complete Cell hw can be emulated by Full System Simulator – Development and porting of applications is easy

Cell Processor (cont.)

IBM ČVUT Student Research Project 2006 (7 z 14)

DSP Library

• SPUC (Signal Processing using C++) library has been ported

to use Cell interface – Basic building blocks (FIR, IIR, Allpass, Lagrange interpolation filters, NCO, Cordic rotator, …) – Communication functions (timing, phase and frequency discriminators for BPSK/QPSK signals) – Various adaptive equalizer classes

• Our example

– Shows the operations above matrixes

IBM ČVUT Student Research Project 2006 (8 z 14)

JPEG Library from IJG

IBM ČVUT Student Research Project 2006 (9 z 14)

• How to maximize utility of SPUs?

– Select the best model (RPC, threads) – Transfer bigger clusters of data and less often – Take advantage of already running threads (don't needlessly spawn new threads)

• Minimize necessary changes to library code

Design Issues

IBM ČVUT Student Research Project 2006 (10 z 14)

Design Issues (cont.)

IBM ČVUT Student Research Project 2006 (11 z 14)

Design Issues (cont.)

IBM ČVUT Student Research Project 2006 (12 z 14)

• Plan

– Library cross-compilation for PPC architecture – Rewrite generic C code to Altivec C intrinsics – Rewrite Altivec intrinsics to SPU intrinsics, add SPU thread activation code to library – Test the library

• The plan was successfully realized

Design Issues (cont.)

IBM ČVUT Student Research Project 2006 (13 z 14)

• Original bmp image before compression
• size 7678 bytes
• JPEG (75% quality)
• size 2362 bytes
• JPEG (15% quality)
• size 1272 bytes

And the results?

IBM ČVUT Student Research Project 2006 (14 z 14)

• Subjects of possible future extensions

– Make compilation & instalation process more friendly – For sure there are other ways how to do the same – try them and test performance – Port the whole jpeg library and not just compression part – Change library in backward compatible manner

• Project pages (password required)

– http://service.felk.cvut.cz/courses/36SPA/prj/36SPA23

• Documentation, Sources, Binaries

Summary