MIT OpenCourseWare
http://ocw.mit.edu
6.189 Multicore Programming Primer, January (IAP) 2007
Please use the following citation format:
Bill Thies, 6.189 Multicore Programming Primer, January (IAP) 2007.
(Massachusetts Institute of Technology: MIT OpenCourseWare).
http://ocw.mit.edu (accessed MM DD, YYYY). License: Creative
Commons Attribution-Noncommercial-Share Alike.
Note: Please use the actual date you accessed this material in your citation.
For more information about citing these materials or our Terms of Use, visit:
http://ocw.mit.edu/terms
6.189 IAP 2007
Lecture 8
The StreamIt Language
Bill Thies, MIT.
1
6.189 IAP 2007 MIT
Languages Have Not Kept Up
Images by MIT OpenCourseWare.
C
von-Neumann
machine
Modern
architecture
● Two choices:
●
„
Develop cool architecture with
complicated, ad-hoc language
language
„
Bend over backwards to support
old languages like C/C++
Images by MIT OpenCourseWare.
Bill Thies, MIT.
2
6.189 IAP 2007 MIT
Why a New Language?
For uniprocessors,
C was:
•Portable
•High Performance
•Composable
•Malleable
•Maintainable
512
256
128
64
32
# of
cores 16
8
4
Pico
Pi
cochip
chip
PC102
Cisco
CSR-1
Intel
Tflops
Raw
Raw
4004
8080
8086
286
386
486
Boardcom 1480
Pentium
8008
1970
Bill Thies, MIT.
1975
1980
1985
1990
3
Razza
Ra
a
XLR
Niagara
2
1
Ambric
Ambric
AM2045
AM
2045
Caviium
Cav
um
Octeon
Cell
Cell
Opteron 4P
Xeon
Xe
on MP
Xbox360
Xbox36
0
PA-8800 Opteron
Tanglewood
Power4
PExtreme
PExtrem
e Power6
Yonah
P2 P3 Itanium
P4
Athlon
Itanium 2
1995
2000
2005
20??
6.189 IAP 2007 MIT
Why a New Language?
512
Pico
Pi
cochip
chip
PC102
Uniprocessors:
128
C is the common
64
machine language
256
Cisco
CSR-1
Intel
Tflops
32
# of
cores 16
Raw
Raw
Razza
Ra
a
XLR
Niagara
8
Boardcom 1480
4
2
1
4004
8080
8086
286
386
486
Pentium
8008
1970
Bill Thies, MIT.
1975
1980
1985
1990
4
Ambric
Ambric
AM2045
AM
2045
Caviium
Cav
um
Octeon
Cell
Cell
Opteron 4P
Xeon
Xe
on MP
Xbox360
Xbox36
0
PA-8800 Opteron
Tanglewood
Power4
PExtreme
PExtrem
e Power6
Yonah
P2 P3 Itanium
P4
Athlon
Itanium 2
1995
2000
2005
20??
6.189 IAP 2007 MIT
Why a New Language?
What is the common
machine language
for multicores?
512
256
128
Picochip
Picochip
PC102
Ambric
Ambric
AM2045
Cisco
Cisco
CSR-1
Intel
Tflops
64
32
# of
cores 16
Raw
Ra
w
Niagara
8
Boardcom
B
oardcom 1480
4
2
1
Raza
Raza
XLR
4004
8080
8086
286
386
486
Pentium
8008
1970
Bill Thies, MIT.
1975
1980
1985
1990
5
Cavium
Cavium
Octeon
Octeon
Cell
Opteron 4P
Xeon MP
Xbox360
Xbox360
PA-8800
PA
-8800 Opteron
Tanglewood
Power4
PExtreme Power6
Yonah
P2 P3 Itanium
P4
Athlon
Itanium 2
1995
2000
2005
20??
6.189 IAP 2007 MIT
Common Machine Languages
Uniprocessors:
Multicores:
Common Properties
Common Properties
Single flow of control
Multiple flows of control
Single memory image
Multiple local memories
Differences:
Differences:
Register File
Number and capabilities of cores
ISA
Communication Model
Functional Units
Synchronization Model
von-Neumann languages represent the
common properties and abstract away
the differences
Need common machine language(s)
for multicores
Bill Thies, MIT.
6
6.189 IAP 2007 MIT
Streaming as a Common Machine Language
AtoD
● For programs based on streams of data
„
„
Audio, video, DSP, networking, and
cryptographic processing kernels
Examples: HDTV editing, radar
tracking, microphone arrays, cell
phone base stations, graphics
● Several attractive properties
„
„
„
Regular and repeating computation
Independent filters
with explicit communication
Task, data, and pipeline parallelism
Bill Thies, MIT.
7
FMDemod
Scatter
LPF1
LPF2
LPF3
HPF1
HPF2
HPF3
Gather
Adder
Speaker
6.189
IAP 2007 MIT
Streaming Models of Computation
● Many different ways to represent streaming
„
„
„
„
Do senders/receivers block?
How much buffering is allowed on channels?
Is computation deterministic?
Can you avoid deadlock?
● Three common models:
1. Kahn Process Networks
2. Synchronous Dataflow
3. Communicating Sequential Processes
Bill Thies, MIT.
8
6.189 IAP 2007 MIT
Streaming Models of Computation
Communication Buffering
Pattern
Notes
Kahn process
networks (KPN)
Data-dependent,
but deterministic
Conceptually
unbounded
- UNIX pipes
- Ambric (startup)
Synchronous
dataflow (SDF)
Static
Fixed by
compiler
- Static scheduling
- Deadlock freedom
Communicating
Sequential
Processes (CSP)
Data-dependent,
allows nondeterminism
None
- Rich synchronization
(Rendesvouz) primitives
- Occam language
SDF
CSP
KPN
space of program behaviors
Bill Thies, MIT.
9
6.189 IAP 2007 MIT
The StreamIt Language
● A high-level, architecture-independent language for
streaming applications
„
„
Improves programmer productivity (vs. Java, C)
Offers scalable performance on multicores
● Based on synchronous dataflow, with dynamic
extensions
„
„
Compiler determines execution order of filters
Many aggressive optimizations possible
Bill Thies, MIT.
10
6.189 IAP 2007 MIT
The StreamIt Project ● Applications
„
„
„
StreamIt Program
DES and Serpent [PLDI 05]
MPEG-2 [IPDPS 06]
SAR, DSP benchmarks, JPEG, …
Front-end
● Programmability
„
„
„
StreamIt Language (CC 02) Teleport Messaging (PPOPP 05)
Programming Environment in Eclipse (P-PHEC 05)
Annotated Java
● Domain Specific Optimizations
„
„
„
Linear Analysis and Optimization (PLDI 03)
Optimizations for bit streaming (PLDI 05)
Linear State Space Analysis (CASES 05)
Simulator
(Java Library)
Stream-Aware
Optimizations
● Architecture Specific Optimizations
„
„
„
„
Compiling for Communication-Exposed Architectures (ASPLOS 02)
Phased Scheduling (LCTES 03)
Cache Aware Optimization (LCTES 05)
Load-Balanced Rendering (Graphics Hardware 05)
Bill Thies, MIT.
11
Uniprocessor
backend
Cluster
backend
Raw
backend
IBM X10
backend
C/C++
MPI-like
C/C++
C per tile +
msg code
Streaming
X10 runtime
6.189 IAP 2007 MIT
Example: A Simple Counter
void->void pipeline Counter() {
add IntSource();
add IntPrinter();
Counter
IntSource
}
void->int filter IntSource() {
int x;
init { x = 0; }
work push 1 { push (x++); }
IntPrinter
% strc Counter.str –o counter
% ./counter –i 4
0
1
2
3
}
int->void filter IntPrinter() {
work pop 1 { print(pop()); }
}
Bill Thies, MIT.
12
6.189 IAP 2007 MIT
Representing Streams
● Conventional wisdom: streams are graphs
„
„
Graphs have no simple textual representation
Graphs are difficult to analyze and optimize
● Insight: stream programs have structure
unstructured
Bill Thies, MIT.
structured
13
6.189 IAP 2007 MIT
Structured Streams
filter
pipeline
may be
any StreamIt
language construct
splitjoin
splitter
● Each structure is singleinput, single-output
● Hierarchical and
composable
parallel computation
joiner
feedback loop
joiner
Bill Thies, MIT.
splitter
14
6.189 IAP 2007 MIT
Filter Example: Low Pass Filter
float->float filter LowPassFilter (int N, float freq) {
float[N] weights;
init {
weights = calcWeights(freq);
N
}
}
work peek N push 1 pop 1 {
float result = 0;
for (int i=0; i<weights.length; i++) {
result += weights[i] * peek(i);
}
push(result);
pop();
}
Bill Thies, MIT.
15
filter
6.189 IAP 2007 MIT
Low Pass Filter in C
void FIR(
int* src,
int* dest,
int* srcIndex,
int* destIndex,
int srcBufferSize,
int destBufferSize,
int N) {
● FIR functionality obscured by
buffer management details
● Programmer must commit to a
particular buffer implementation
strategy
float result = 0.0;
for (int i = 0; i < N; i++) {
result += weights[i] * src[(*srcIndex + i) % srcBufferSize];
}
dest[*destIndex] = result;
*srcIndex = (*srcIndex + 1) % srcBufferSize;
*destIndex = (*destIndex + 1) % destBufferSize;
}
Bill Thies, MIT.
16
6.189 IAP 2007 MIT
Pipeline Example: Band Pass Filter
float→float pipeline BandPassFilter (int N,
float low,
float high) {
add LowPassFilter(N, low);
add HighPassFilter(N, high);
LowPassFilter
HighPassFilter
}
Bill Thies, MIT.
17
6.189 IAP 2007 MIT
SplitJoin Example: Equalizer
float→float pipeline Equalizer (int N,
float lo,
float hi) {
Equalizer
duplicate
add splitjoin {
split duplicate;
for (int i=0; i<N; i++)
BPF
BPF
BPF
add BandPassFilter(64, lo + i*(hi - lo)/N);
join roundrobin(1);
}
roundrobin
add Adder(N);
}
Adder
Bill Thies, MIT.
18
6.189 IAP 2007 MIT
Building Larger Programs: FMRadio
void->void pipeline FMRadio(int N, float lo, float hi) {
add AtoD();
add FMDemod();
FMDemod
add splitjoin {
split duplicate;
for (int i=0; i<N; i++) {
add pipeline {
Duplicate
}
add LowPassFilter(lo + i*(hi - lo)/N);
LPF1
LPF2
LPF3
add HighPassFilter(lo + i*(hi - lo)/N);
HPF1
HPF2
HPF3
}
join roundrobin();
}
add Adder();
RoundRobin
Adder
add Speaker();
}
AtoD
Bill Thies, MIT.
Speaker
19
6.189 IAP 2007 MIT
The Beauty of Streaming
“Some programs are elegant, some are
exquisite, some are sparkling. My claim
is that it is possible to write grand programs,
noble programs, truly magnificient ones!”
— Don Knuth, ACM Turing Award Lecture
Image removed due to copyright restrictions.
Bill Thies, MIT.
20
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
21
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
22
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
23
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
24
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
25
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
26
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
27
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
28
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
29
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
30
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
31
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
32
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
33
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(N)
34
join roundrobin(N)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
35
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
36
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
37
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
38
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
39
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
40
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
41
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
42
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
43
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
44
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
45
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
46
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
47
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
48
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
49
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
50
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
51
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
52
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
53
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
54
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
55
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
56
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
57
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
58
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
59
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
60
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(1)
61
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
62
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
63
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
64
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
65
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
66
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
67
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
68
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
69
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
Bill Thies, MIT.
split roundrobin(2)
70
join roundrobin(1)
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
split roundrobin(2)
join roundrobin(1,2,3)
Bill Thies, MIT.
71
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
split roundrobin(2)
join roundrobin(1,2,3)
Bill Thies, MIT.
72
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
split roundrobin(2)
join roundrobin(1,2,3)
Bill Thies, MIT.
73
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
split roundrobin(2)
join roundrobin(1,2,3)
Bill Thies, MIT.
74
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
split roundrobin(2)
join roundrobin(1,2,3)
Bill Thies, MIT.
75
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
split roundrobin(2)
join roundrobin(1,2,3)
Bill Thies, MIT.
76
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
split roundrobin(2)
join roundrobin(1,2,3)
Bill Thies, MIT.
77
6.189 IAP 2007 MIT
SplitJoins are Beautiful
split duplicate
split roundrobin(2)
join roundrobin(1,2,3)
Bill Thies, MIT.
78
6.189 IAP 2007 MIT
Matrix Transpose
N
M
Transpose
M
N
Bill Thies, MIT.
79
6.189 IAP 2007 MIT
Matrix Transpose
N
M
roundrobin(?)
?
roundrobin(?)
M
N
Bill Thies, MIT.
80
6.189 IAP 2007 MIT
Matrix Transpose
N
M
roundrobin(?)
?
roundrobin(?)
M
N
Bill Thies, MIT.
81
6.189 IAP 2007 MIT
Matrix Transpose
N
M
roundrobin(1)
N
roundrobin(M)
M
N
Bill Thies, MIT.
82
6.189 IAP 2007 MIT
Matrix Transpose
N
M
roundrobin(1)
N
roundrobin(M)
M
N
Bill Thies, MIT.
83
6.189 IAP 2007 MIT
Matrix Transpose
N
M
roundrobin(1)
N
roundrobin(M)
float->float splitjoin Transpose (int M,
int N) {
split roundrobin(1);
for (int i = 0; i<N; i++) {
add Identity<float>;
}
join roundrobin(M);
}
M
N
Bill Thies, MIT.
84
6.189 IAP 2007 MIT
Bit-reversed ordering
● Many FFT algorithms require a bit-reversal stage
● If item is at index n (with binary digits b0 b1 … bk),
then it is transferred to reversed index bk … b1 b0
● For 3-digit binary numbers:
00001111
00110011
01010101
00001111
00110011
01010101
Bill Thies, MIT.
85
6.189 IAP 2007 MIT
Bit-reversed ordering
● Many FFT algorithms require a bit-reversal stage
● If item is at index n (with binary digits b0 b1 … bk),
then it is transferred to reversed index bk … b1 b0
● For 3-digit binary numbers:
00001111
00110011
01010101
RR(w1)
00001111
00110011
01010101
Bill Thies, MIT.
RR(w1)
RR(w1)
RR(w2)
RR(w2)
RR(w3)
86
6.189 IAP 2007 MIT
Bit-reversed ordering
● Many FFT algorithms require a bit-reversal stage
● If item is at index n (with binary digits b0 b1 … bk),
then it is transferred to reversed index bk … b1 b0
● For 3-digit binary numbers:
00001111
00110011
01010101
RR(1)
00001111
00110011
01010101
Bill Thies, MIT.
RR(1)
RR(1)
RR(2)
RR(2)
RR(4)
87
6.189 IAP 2007 MIT
Bit-reversed ordering
complex->complex pipeline BitReverse (int N) {
if (N==2) {
add Identity<complex>;
rr
1
1
} else {
rr
1
1
1
add splitjoin {
2
split roundrobin(1);
2
2
rr
add BitReverse(N/2);
4
4
rr
add BitReverse(N/2);
join roundrobin(N/2);
}
}
}
Bill Thies, MIT.
88
1
rr
1
1
rr
1
1
2
2
rr
rr
rr
rr
1
1
1
2
2
4
8
rr
rr
4
8
6.189 IAP 2007 MIT
rr
rr
1
2
N-Element Merge Sort
int->int pipeline MergeSort (int N) {
if (N==2) {
add Sort(N);
} else {
add splitjoin {
split roundrobin(N/2);
add MergeSort(N/2);
add MergeSort(N/2);
join roundrobin(N/2);
}
}
add Merge(N);
}
Bill Thies, MIT.
89
N
N/2
N/8
Sort
N/4
N/4
N/4
N/8
N/2
N/8
N/8
Sort
Merge
N/8
N/8
Sort
Sort
Sort
Merge
N/4
Sort
Sort
Merge
Merge
N/8
N/8
Sort
Merge
Merge
Merge
6.189 IAP 2007 MIT
N-Element Merge Sort (3-level)
N
N/2
N/2
N/4
N/4
N/4
N/4
N/8
N/8
N/8
N/8
N/8
N/8
N/8
N/8
Sort
Sort
Sort
Sort
Sort
Sort
Sort
Sort
Merge
Merge
Merge
Merge
Merge
Merge
Merge
Bill Thies, MIT.
90
6.189 IAP 2007 MIT
Bitonic Sort
Courtesy of William Thies.
Used with permission.
Bill Thies, MIT.
91
6.189 IAP 2007 MIT
FFT
Courtesy of William Thies.
Used with permission.
Bill Thies, MIT.
92
6.189 IAP 2007 MIT
Block Matrix Multiply
Courtesy of William Thies.
Used with permission.
Bill Thies, MIT.
93
6.189 IAP 2007 MIT
Filterbank
Courtesy of William Thies.
Used with permission.
Bill Thies, MIT.
94
6.189 IAP 2007 MIT
FM Radio with Equalizer
Courtesy of William Thies.
Used with permission.
Bill Thies, MIT.
95
6.189 IAP 2007 MIT
Radar-Array Front End
Courtesy of William Thies.
Used with permission.
Bill Thies, MIT.
96
6.189 IAP 2007 MIT
MP3 Decoder
Courtesy of William Thies.
Used with permission.
Bill Thies, MIT.
97
6.189 IAP 2007 MIT
Case Study:
MPEG-2 Decoder in StreamIt
Bill Thies, MIT.
98
6.189 IAP 2007 MIT
MPEG-2 Decoder in StreamIt
MPEG bit stream
picture type
add VLD(QC, PT1, PT2);
VLD
quantization coefficients
split roundrobin(N∗B, V);
splitter
<QC>
<PT1, PT2>
add splitjoin {
macroblocks, motion vectors
frequency encoded
macroblocks
differentially coded
motion vectors
add pipeline {
add ZigZag(B);
add IQuantization(B) to QC;
add IDCT(B);
add Saturation(B);
}
add pipeline {
add MotionVectorDecode();
add Repeat(V, N);
}
ZigZag
Motion Vector Decode
<QC> IQuantization
IDCT
Repeat
Saturation
spatially encoded macroblocks
motion vectors
join roundrobin(B, V);
joiner
}
Y
add splitjoin {
split roundrobin(4∗(B+V), B+V, B+V);
splitter
Cb
Cr
add MotionCompensation(4∗(B+V)) to PT1;
for (int i = 0; i < 2; i++) {
add pipeline {
add MotionCompensation(B+V) to PT1;
add ChannelUpsample(B);
}
}
Motion Compensation Motion Compensation Motion Compensation
<PT1> reference
<PT1> reference
<PT1> reference
picture
picture
picture
Channel Upsample
Channel Upsample
joiner
recovered picture
join roundrobin(1, 1, 1);
}
<PT2> Picture Reorder
add PictureReorder(3∗W∗H) to PT2;
add ColorSpaceConversion(3∗W∗H);
Color Space Conversion
Bill Thies, MIT.
output to player
99
6.189 IAP 2007 MIT
Teleport Messaging in MPEG-2
VLD
picture type
IQ
splitter
Y
Motion
Compensation
MC
Cr
Cb
Motion
Compensation
Motion
Compensation
Channel
Upsample
Channel
Upsample
MC
MC
joiner
recovered picture
Order
Bill Thies, MIT.
100
6.189 IAP 2007 MIT
Messaging Equivalent in C
The MPEG Bitstream
File Parsing
Decode Macroblock
ZigZagUnordering
Decode Block
Inverse
Quantization
Global Variable
Space
Decode
Picture
Saturate
Decode
Motion
Vectors
Motion Compensation
IDCT
Motion Compensation For Single Channel
Frame Reordering
Output Video
Bill Thies, MIT.
101
6.189 IAP 2007 MIT
MPEG-2 Implementation
● Fully-functional MPEG-2 decoder and encoder
● Developed by 1 programmer in 8 weeks
● 2257 lines of code
„
Vs. 3477 lines of C code in MPEG-2 reference
● 48 static streams, 643 instantiated filters
Bill Thies, MIT.
102
6.189 IAP 2007 MIT
Conclusions
● StreamIt language preserves program structure
„
Natural for programmers
● Parallelism and communication naturally exposed
„
Compiler managed buffers, and portable parallelization
technology
● StreamIt increases programmer productivity, enables
parallel performance
Bill Thies, MIT.
103
6.189 IAP 2007 MIT