Mapping of Streaming Applications considering

Alternative Application Specifications (Extended Abstract)

Jiali Teddy Zhai, Hristo Nikolov, Todor StefanovLeiden Institute of Advanced Computer Science (LIACS), Leiden University, The Netherlands

{tzhai, nikolov, stefanov}@liacs.nl

Pre-print of the full paper can be found under: http://www.liacs.nl/~tzhai/pdf/Zhai-TECS2012.pdf

Abstract—Streaming applications often require a parallel Model ofComputation (MoC) to specify their application behavior and to facili-

tate mapping onto Multi-Processor System-on-Chip (MPSoC) platforms.Various performance requirements and resource budgets of embeddedsystems ask for an efficient design space exploration (DSE) approach toselect the best design from a design space consisting of a large number

of design choices. However, existing DSE approaches explore the designspace that includes only architecture and mapping alternatives for aninitial application specification given by the application designer. In thispaper, we first show that a design often might not be optimal if alternative

specifications of a given application are not taken into account. We furtherargue that the best alternative specification consists of only independentand load-balanced application tasks. Based on the Polyhedral ProcessNetwork (PPN) MoC, we present an approach to analyze and transform

an initial PPN to an alternative one that contains only independentprocesses if possible. Finally, by prototyping real-life applications on bothFPGA-based MPSoCs and desktop multi-core platforms, we demonstrate

that mapping the alternative application specification results in a largeperformance gain compared to those approaches, in which alternativeapplication specifications are not taken into account.

I. INTRODUCTION

Streaming applications are widely used in several domains. Strin-

gent performance requirements have been driving the implementation

of streaming applications on Multi-Processor System-on-Chip (MP-

SoC) platforms, which contain an increasing number of Processing

Elements (PEs).

To enable an efficient design of streaming applications on MPSoC

platforms, application behavior is usually specified using a certain

parallel Model of Computation (MoC). However, a given application

specification in a MoC may not be the most appropriate one for the

considered MPSoC platform. This is because application designers

may not fully take the computational capacity and communication

cost of the MPSoC platform into account. Therefore, often the initial

application specification only leads to an inferior design. In this

case, alternative application specifications may be needed for efficient

design of an application on MPSoC platforms. In general, the best

application specification, if it exists, to be mapped onto n PEs is

the one that consists of n communication-free and load-balanced

tasks. In this paper, we study the problem of whether an alternative

specification exists, which consists of only communication-free and

load-balanced tasks, for an initial parallel application specification.

II. PAPER CONTRIBUTIONS

For an application modeled using the Polyhedral Process Network

(PPN) MoC [1], we devise an approach to analytically determine

the maximum amount of data-level parallelism, i.e., the number of

communication-free partitions. Subsequently, we propose a procedure

to transform the initial PPN to a set of communication-free partitions,

if they exist. Our approach also can be applied to applications with

cyclic dependences, which are traditionally considered as perfor-

mance bottleneck and hard to parallelize. Finally, we demonstrate

and validate the effectiveness of our approach by prototyping real-

�

�

�

�

�

�

�

�

� � � � � � �

�������

������������� ������� �

�� ���

�� ���� ���

(a)

���

�

���

�

���

�

���

� � � � � �

�������

������������� �

�� � ��

�������� ��

(b)

Fig. 1. Performance results of mapping the FM radio application onto (a)FPGA-based MPSoC platforms and onto (b) a desktop multi-core platform.

life streaming applications on FPGA-based MPSoCs and a desktop

multi-core platform.

III. CASE STUDIES

We performed case studies on two real-life applications modeled

using the PPN MoC, namely a Motion-JPEG (MJPEG) encoder

and the FM radio application taken from the StreamIT benchmark

suite [2]. All experiments were conducted using the open-source

ESPAM [3] tool on two different platforms, a Xilinx ML605 FPGA

board with up to 8 MicroBlaze (MB) soft-cores and a desktop multi-

core platform containing an Intel i7-920 processor with 4 cores. Due

to limited space, here we only show the performance results for the

FM radio application in Fig. 1(a) and 1(b). Compared to mapping

the initial application specification by optimally pipelining, mapping

the alternative PPN (denoted as Alternative in Fig. 1(a)) outperforms

mapping the initial PPN by 32.05% to 97.74% on 3 to 7 MBs on

the FPGA-based platform. A 7.83X speedup is achieved on 8 MBs.

On the desktop platform, our approach (denoted as Alternative in

Fig. 1(b)) outperforms the mapping of the initial PPN by 39.79% to

489.27% using 2 to 7 threads. In the best case, 3.46X speedup is

observed using 7 threads.

To quantify the time complexity of our approach, we conducted ex-

periments on a set of real-life benchmarks. In practice, our approach

takes less than 3 seconds to derive all communication-free partitions

for the considered benchmarks.

REFERENCES

[1] S. Verdoolaege, H. Nikolov, and T. Stefanov, “pn: a tool for improvedderivation of process networks,” EURASIP J. Embedded Syst., 2007.

[2] M. I. Gordon, W. Thies, and S. Amarasinghe, “Exploiting coarse-grainedtask, data, and pipeline parallelism in stream programs,” in Proc. ASPLOS,2006, pp. 151–162.

[3] H. Nikolov, T. Stefanov, and E. Deprettere, “Systematic and automatedmultiprocessor system design, programming, and implementation,” IEEE

Trans. Comput.-Aided Design Integr. Circuits Syst., vol. 27, pp. 542–555,2008.

27978-1-4673-4967-3/12/$31.00 ©2012 IEEE