Component-Based Programming with Streams

Philip GarciaUniversity of Wisconsin - Madison

Johannes HelanderMicrosoft Research

Component Based Programming

• Program viewed as a collection of autonomous components

• Each component performs a single task• Components can be combined in various ways

to execute different applications• Each component can execute simultaneously*

Component-based design• Overall system design described in XML– Describe individual components– Describe Components interconnection– Describe application as interconnection of components

• Components – Written in “traditional” languages (C/C++)– Interface with buffer streams– Stream elements

accessed using buffer “windows”

– System automatically handles concurrency when window is advanced, or changes in size

Example Windows

Data Windows

• Virtualize accesses into data buffers that exist between components

• Dynamically handles concurrency between components

• Allows array-like access into shared buffers– However, accesses must occur within the defined

window– Window can expand, shrink, or advance– Windows can not move backward

Example Component

Test Benchmark• JPEG Encoding

Components needed to convert a bitmap into a JPEG

Application’s XML Description<AppStream xmlns="http://tempuri.org/X-Buffer/0.01">

<Stream> <Component type="COB\CFromPPM.cob" name="Source" init="true"/>

<Component type="COB\CColorConv.cob" name=“Conv" init="false"/> <Component type="COB\CFDCT.cob" name=“DCT" init="false"/> <Component type="COB\CQuant.cob" name=“Quant" init="false"/> <Component type="COB\CHuff.cob" name=”Drain" init="false"/>

</Stream> <Chain>

<link><name>Source</name><Win>0</Win></link><link><name>Conv</name><Win>1</Win></link>

</Chain>contd….

Description continued<Chain>

<link><name>Conv</name><Win>0</Win></link> <link><name>DCT</name><Win>1</Win></link>

</Chain> <Chain>

<link><name>DCT</name><Win>0</Win></link> <link><name>Quant</name><Win>1</Win></link> </Chain> <Chain>

<link><name>VQuant</name><Win>0</Win></link> <link><name>Wdrain</name><Win>0</Win></link> </Chain> <Initializer>SestupJPEG</Initializer>

</AppStream>

JPEG Profile

• Obtained profiling data in Linux using gprof– Baseline ran under windows using MS VS compiler– Windows execution time (256MB input): 7.33s– Linux execution time (256MB input): 4.05s

Routine Execution Percentage

Color Conversion 30%

Huffman Encoding 26%

Quantization 26%

Forward DCT 13%

“Speedup” over baseline

Poor Scaling

• MMLite Development environment was not designed for windows– Embedded systems development– Windows support was an afterthought added for

debugging– Heavy-weight communication primitives

• Compiler Optimizations ?– Need to obtain a good windows profiling tool– Find performance bottlenecks

Multiprocessor Scaling

Thoughts on Application Porting

• Using pre-built buffer streams greatly simplified development

• Resulting code was much simpler than the original baseline

• Additional options can be added by swapping out components (rather than setting flags)

Questions

Specifying Components

• Each component implements a standard interface.– Initialization– Execution

• XML file describes system– Lists all components used– Describes communication between components– Specifies Initialization routine*

Example<AppStream xmlns="http://tempuri.org/X-Buffer/0.01"> <Stream> <Component type="COB\CFromEP.cob" name="Source" init="true"/> <Component type="COB\Base64Encoder.cob" name="Encode" init="false"/> <Component type="COB\CToEP.cob" name="Drain" init="true"/> </Stream> <Chain> <link><name>Source</name><Win>0</Win></link> <link><name>Encode</name><Win>0</Win></link> </Chain> <Chain> <length>2</length> <link><name>Encode</name><Win>1</Win></link> <link><name>Drain</name><Win>0</Win></link> </Chain><Initializer>SetupEP</Initializer></AppStream>

How do we define components?

• Each component written in traditional language– Allows reuse of existing routines and algorithms– Programmers are familiar with environment– Currently only support components written in C– Plan to add support for Hardware-based

components

System Execution

• System compiles XML description into C– Initializes each component– Initializes buffer streams/windows– Can run each component as separate thread– Statically or dynamically schedules threads

• Eventual goal is to allow components to be software or hardware