parallel programming and timing analysis on embedded multicores eugene yip the university of...

1

Parallel Programmingand Timing Analysis

on Embedded Multicores

Eugene YipThe University of Auckland

Supervisors: Advisor:Dr. Partha Roop Dr. Alain GiraultDr. Morteza Biglari-Abhari (INRIA)(UoA)

2

Outline

• Introduction• ForeC Language• Timing Analysis• Results• Conclusions

3

Outline


4

Introduction

• Safety-critical systems:

– Perform specific real-time tasks.– Comply with strict safety standards

[IEC 61508, DO 178]– Time-predictability useful in real-time designs.

[Paolieri et al 2011] Towards Functional-Safe Timing-Dependable Real-Time Architectures.

Embedded Systems

Safety-critical concerns

Timing/Functionality requirements

5

Introduction

• Safety-critical systems:– Shift from single-core to multicore processors.– Cheaper, better power vs. execution performance.

Coren

Core0

System bus

Resource Resource

Shared

Shared Shared[Blake et al 2009] A Survey of Multicore Processors.[Cullmann et al 2010] Predictability Considerations in the Design of Multi-Core Embedded Systems.

6

Introduction

• Parallel programming:– From super computers to mainstream computers.– Frameworks designed for systems without

resource constraints or safety-concerns.• Optimised for average-case performance (FLOPS), not

time-predictability.

– Threaded programming model.• Pthreads, OpenMP, Intel Cilk Plus, ParC, ...• Non-deterministic thread interleaving makes

understanding and debugging hard.

[Lee 2006] The Problem with Threads.

7

Introduction

• Parallel programming:– Programmer responsible for shared resources.– Concurrency errors:• Deadlock, Race condition, Atomic violation, Order

violation.

[McDowell et al 1989] Debugging Concurrent Programs.[Lu et al 2008] Learning from Mistakes: A Comprehensive Study on Real World Concurrency Bug Characteristics.

8

Introduction

• Synchronous languages:– Deterministic concurrency (formal semantics).– Execution model similar to digital circuits.• Threads execute in lock-step to a global clock.• Threads communicate via instantaneous signals.

– Concurrency is logical. Typically compiled away.

[Benveniste et al 2003] The Synchronous Languages 12 Years Later.

Global ticks

Inputs

Outputs1 2 3 4

9

Introduction

• Synchronous languages:

Physical time1s 2s 3s 4s

Time for a tick

Must validate:max(Reaction time) < min(Time for each tick)

Reaction time

Specified by the system’s timing requirements


10

Introduction

• Synchronous languages– Esterel, Lustre, Signal– Synchronous extensions to C:• PRET-C• Reactive Shared Variables• Synchronous C• Esterel C Language

[Roop et al 2009] Tight WCRT Analysis of Synchronous C Programs.[Boussinot 1993] Reactive Shared Variables Based Systems.[Hanxleden et al 2009] SyncCharts in C - A Proposal for Light-Weight, Deterministic Concurrency.[Lavagno et al 1999] ECL: A Specification Environment for System-Level Design.

Retain the essence of C and add deterministic concurrency and thread communication.

11

Introduction



Concurrent threads scheduled sequentially in a cooperatively manner. This ensures thread-safe access to shared variables.

Semantics designed to facilitate static analysis.

12

Introduction



Read phase followed by write phase for shared variables.

Multiple writes to the same shared variable are combined using an associative and commutative “combine function”.

13

Introduction



More expressive than PRET-C, but static timing analysis hasn’t been formulated yet.

14

Introduction



Sequential execution semantics. Unsuitable for parallel execution.

15

Introduction



Compilation produces sequential programs. Unsuitable for parallel execution.

16

Outline


17

ForeC Language

“Foresee” ForeC • C-based, multi-threaded, synchronous

language. Inspired by PRET-C and Esterel.• Deterministic parallel execution on embedded

multicores.• Fork/join parallelism and shared memory

thread communication.• Program behaviour independent of chosen

thread scheduling.

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ForeC Language

• Additional constructs to C:– pause: Synchronisation barrier. Pauses the

thread’s execution until all threads have paused.– par( st1, ..., stn ): Forks each statement to

execute as a parallel thread. Each statement is implicitly scoped.

– [weak] abort st when [immediate] exp: Preempts the statement st when exp evaluates to a non-zero value. exp is evaluated in each global tick before st is executed.

19

ForeC Language

• Additional variable type-qualifiers to C:– input and output: Declares a variable whose

value is updated or emitted to the environment at each global tick.

20

ForeC Language

• Additional variable type-qualifiers to C:– shared: Declares a shared variable that can be

accessed by multiple threads.

21

ForeC Language

• Additional variable type-qualifiers to C:– shared: Declares a shared variable that can be

accessed by multiple threads. 1. Threads make local copies of shared variables that they

may use at the start of their local ticks.2. Threads only modify their local copies during execution.3. If a par statement terminates:

• Modified copies from the child threads are combined (using a commutative & associative function) and assigned to the parent.

3. If the global tick ends:• The modified copies are combined and assigned to the actual

shared variables.

a

b

22

Execution Exampleshared int sum = 1 combine with plus;

int plus(int copy1, int copy2) { return (copy1 + copy2);}

void main(void) { par(f(1), f(2));}

void f(int i) { sum = sum + i; pause; ...}

Synchronisation

Fork-join

Shared variable

Commutative and associative combine function

23





Global

sum = 1

24





Global

sum = 1Global tick start

25





Global Local

f1 f2

sum = 1

sum1 = 1 sum2 = 1

Global tick start

26





Global Local

f1 f2

sum = 1

sum1 = 1sum1 = 2

sum2 = 1sum2 = 3

Global tick start

27





Global Local

f1 f2

sum = 1

sum1 = 1sum1 = 2

sum2 = 1sum2 = 3

Global tick start

Global tick end

28





Global Local

f1 f2

sum = 1

sum1 = 1sum1 = 2

sum2 = 1sum2 = 3

sum = 5

Global tick start

Global tick end

29





Global Local

f1 f2

sum = 1

sum1 = 1sum1 = 2

sum2 = 1sum2 = 3

sum = 5

sum1 = 5. . .

sum2 = 5. . .

Global tick start

Global tick end

Global tick start

30

Execution Example

Shared variables:– Threads modify local copies of shared variables.• Isolation of thread execution allows threads to truly

execute in parallel.• Thread interleaving does no affect the program’s

behaviour.

– Prevents most concurrency errors.• Deadlock, Race condition: No locks.• Atomic and order violation: Local copies.

– Copies for a shared variable can be split into groups and combined in parallel.

31

Execution Example

Shared variables:– Programmer has to define a suitable combine

function for each shared variable.• Must ensure the combine function is indeed

commutative & associative.

– Notion of “combine functions” is not entirely new:• Intel Cilk Plus, OpenMP, MPI, UPC, X10• Esterel, Reactive Shared Variables

[Intel Cilk Plus] http://software.intel.com/en-us/intel-cilk-plus [OpenMP] http://openmp.org[MPI] http://www.mcs.anl.gov/research/projects/mpi/ [Unified Parallel C] http://upc.lbl.gov/ [X10] http://x10-lang.org/[Berry et al 1992] The Esterel Synchronous Programming Language: Design, Semantics and Implementation.[Boussinot 1993] Reactive Shared Variables Based Systems.

32


Execution Example

Shared variables: – Programmer has to define a suitable combine




cilk::reducer_opcilk::holder_op

shared varreduction(operator: var)

MPI_ReduceMPI_Gather

shared varcollectives

Aggregates

33


Execution Example

Shared variables: – Programmer has to define a suitable combine




Valued signalsCombine operator

shared varCombine operator

34

Shared Variable Design Patterns

• Point-to-point• Broadcast• Software pipelining• Divide and conquer– Scatter/Gather– Map/Reduce

35

Overview of the Framework

Thread distribution

ForeCsource code

CCFG

Static scheduling

Compiled program

CCFG with assembly

Architecture model

ReachabilityComputed

WCRT

Compilation Timing AnalysisProgramming

36

Concurrent Control Flow Graph

shared int sum = 1 combine with plus;




Fork

Join

Computation

Condition

Pause

Abort

Graph End

Graph Start

f1 f2

main

37

Scheduling

• Light-Weight Static Scheduling:– Take advantage of multicore performance while

delivering time-predictability.– Generate code to execute directly on hardware

(bare metal/no OS).– Thread allocation and scheduling order on each

core decided at compile time by the programmer.• Develop a WCRT-aware scheduling heuristic.• Thread isolation allows for scheduling flexibility.

– Cooperative (non-preemptive) scheduling.

38

Scheduling

• Cores synchronise to fork/join threads and end each global tick.

• One core to perform housekeeping tasks at the end of the global tick:– Combining shared variables.– Emitting outputs.– Sampling inputs and trigger the next global tick.

39

Outline


40

Timing Analysis

Compute the program’s worst-case reaction time (WCRT).

Physical time1s 2s 3s 4s

Time for a tick

Must validate:max(Reaction time) < min(Time for each tick)

Reaction time

Specified by the system’s timing requirements


41

Timing Analysis

Existing approaches for synchronous programs:• Integer Linear Programming (ILP)• “Coarse-grained” Reachability (Max-Plus)• Model Checking

One existing approach for analysing the WCRT of synchronous programs on multicores:• [Ju et al 2010] Timing Analysis of Esterel Programs on General-Purpose

Multiprocessors.• Uses ILP, no tightness result, all experiments performed 4-core processor.

42

Timing Analysis

Existing approaches for synchronous programs.• Integer Linear Programming (ILP)– Execution time of the program described as a set

of integer equations.– Solving ILP is NP-complete.

[Ju et al 2010] Timing Analysis of Esterel Programs on General-Purpose Multiprocessors.

43

Timing Analysis

Existing approaches for synchronous programs.• “Coarse-grained” Reachability (Max-Plus)– Compute the WCRT of each thread.– Using the thread WCRTs, the WCRT of the program

is computed.– Assumes there is a global tick where all threads

execute their worst-case.

[M. Boldt et al 2008] Worst Case Reaction Time Analysis of Concurrent Reactive Programs.

44

Timing Analysis

Existing approaches for synchronous programs.• Model Checking– Computes the execution time along all possible

execution paths.– State-space explosion problem.– Binary search: Check the WCRT is less than “x”.– Trades-off analysis time for precision.– Counter example: Execution trace for the WCRT.

[P. S. Roop et al 2009] Tight WCRT Analysis of Synchronous C Programs.

45

Timing Analysis

Proposed “fine-grained” Reachability approach:• Only consider local ticks that can execute

together in the same global tick.• Timed execution trace for the WCRT.• To handle the state-space explosion:– Reduce the program’s CCFG before analysis.

Program binary

(annotated)

Find all global ticks

(Reachability)WCRT

Reconstruct the program’s

CCFG

46

Timing Analysis

Programs executed on the following multicore architecture:

Core0

TDMA Shared Bus

Global memory

Datamemory

Instruction memory Core

nDatamemory

Instruction memory

47

Timing Analysis

Computing the execution time:1. Overlapping of thread execution time from

parallelism and inter-core synchronizations.2. Scheduling overheads.3. Variable delay in accessing the shared bus.

48

Timing Analysis

1. Overlapping of thread execution time from parallelism and inter-core synchronisations.• An integer counter to track each core’s execution time.• Synchronisation occurs when forking/joining, and ending

the global tick.• Advance the execution time of participating cores.

Core 1: Core 2:main f2

f1

Core 1 Core 2

mainf2f1

f1 f2

main

49

Timing Analysis

2. Scheduling overheads.– Synchronisation: Fork/join and global tick.

• Via global memory.

– Thread context-switching.• Copying of shared variables at the start the thread’s

local tick via global memory.

Synchronisation

Thread context-switch

Core 1 Core 2

mainf2f1

Global tick

50

Timing Analysis

2. Scheduling overheads.– Required scheduling routines statically known.– Analyse the scheduling control-flow.– Compute the execution time for each scheduling

overhead. Core 1 Core 2

main

f1

Core 1 Core 2

mainf2f1

f2

51

Timing Analysis

3. Variable delay in accessing the shared bus.– Global memory accessed by scheduling routines.– TDMA bus delay has to be considered.

Core 1 Core 2

main

f1 f2

52

Timing Analysis


121212121212

Core 1 Core 2

slotsCore 1 Core 2

main

f1 f2

53

Timing Analysis


121212121212

Core 1 Core 2

main

f1f2

Core 1 Core 2

main

f1 f2

54

Timing Analysis

CCFG optimisations:– merge: Reduces the number of CFG nodes that

need to be traversed.– merge-b: Reduces the number of alternate paths

in the CFG. (Reduces the number of global ticks)– Precision of the analysis is unaffected because we

are not performing value analysis to prune infeasible paths.

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Timing Analysis

CCFG optimisations:– merge: Reduces the number of CFG nodes that

need to be traversed.– merge-b: Reduces the number of alternate paths

in the CFG. (Reduces the number of global ticks)

cost = 1

cost = 4

cost = 3

cost = 1

cost= 1 + 3= 4

cost= 1 + 4 + 1= 6

cost = 6

merge merge-b

56

Outline


57

Results

For the proposed reachability-based timing analysis, we demonstrate:– the precision of the computed WCRT.– the efficiency of the analysis, in terms of analysis

time.

58

Results

Timing analysis tool:

Program binary

(annotated)

Fine-grained Reachability(Proposed)

Coarse-grained

Reachability(Max-Plus)

Taking into account the 3 factors

WCRTProgram CCFG (optimisations)

59

Results

Multicore simulator (Xilinx MicroBlaze):– Based on http://www.jwhitham.org/c/smmu.html

and extended to be cycle-accurate and support multiple cores and a TDMA bus.

Core0

TDMA Shared Bus

Global memory

Datamemory

Instruction memory Core

nDatamemory

Instruction memory16KB

16KB

32KB5 cycles

1 cycle

5 cycles/core(Bus schedule round = 5 * no. cores)

http://www.jwhitham.org/c/smmu.html

http://www.jwhitham.org/c/smmu.html

60

Results

• Mix of control/data computations, thread structure and computation load.

* [Pop et al 2011] A Stream-Computing Extension to OpenMP.# [Nemer et al 2006] A Free Real-Time Benchmark.

*

*

#

Benchmark programs.

61

Results

• Each benchmark program was distributed over varying number of cores.– Up to the maximum number of parallel threads.

• Observed the WCRT:– Test vectors to elicit different execution paths.

• Computed the WCRT:– Proposed– Max-Plus

62

802.11a Results

Observed:• WCRT decreases

until 5 cores.• Global memory

increasingly expensive.

• Scheduling overheads.

1 2 3 4 5 6 7 8 9 100

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

200,000

Observed

Proposed

MaxPlus

Cores

WC

RT

(cl

ock

cyc

les)

63

802.11a Results

1 2 3 4 5 6 7 8 9 100

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

200,000

Observed

Proposed

MaxPlus

Cores

WC

RT

(cl

ock

cyc

les)

Proposed:• ~2% over-

estimation.• Benefit of fine-

grained reachability.

64

802.11a Results

Max-Plus:• Loss of execution

context: Uses only the thread WCRTs.

• Assumes one global tick where all threads execute their worst-case.

• Max execution time of the scheduling routines.1 2 3 4 5 6 7 8 9 10

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

200,000

Observed

Proposed

MaxPlus

Cores

WC

RT

(cl

ock

cyc

les)

65

802.11a Results

Both approaches:• Estimation of

synchronisation cost is conservative. Assumed that the receive only starts after the last sender.

1 2 3 4 5 6 7 8 9 100

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

200,000

Observed

Proposed

MaxPlus

Cores

WC

RT

(cl

ock

cyc

les)

66

802.11a Results

1 2 3 4 5 6 7 8 9 100

500

1,000

1,500

2,000

2,500

Cores

An

alys

is T

ime

(sec

ond

s)

Max-Plus takes less than 2 seconds.Proposed

67

802.11a Results

1 2 3 4 5 6 7 8 9 100

500

1,000

1,500

2,000

2,500

Cores

An

alys

is T

ime

(sec

ond

s)

Proposed (merge)

ProposedMax-Plus takes less than 2 seconds.

merge:• Reduction of ~9.34x

68

802.11a Results

1 2 3 4 5 6 7 8 9 100

500

1,000

1,500

2,000

2,500

Cores

An

alys

is T

ime

(sec

ond

s)

Proposed (merge)

Proposed (merge-b)

ProposedMax-Plus takes less than 2 seconds.

merge:• Reduction of ~9.34xmerge-b:• Reduction of ~342x• Less than 7 sec.

69

Results

Reduction in states reduction in analysis time

Number of global ticks explored.

70

Results

Proposed:• ~1 to 8% over-estimation.• Loss in precision mainly from over-estimating the synchronisation

costs.

1 2 3 40

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

FmRadio

Cores

1 2 3 4 5 6 70

1,000

2,000

3,000

4,000

5,000

6,000

7,000

Fly by Wire

Cores

1 2 3 4 5 6 7 80

20,000

40,000

60,000

80,000

100,000

120,000

140,000

Life

Cores1 2 3 4 5 6 7 8

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

Matrix

Observed

Proposed

MaxPlus

Cores

71

Results

Max-Plus:• Over-estimation very dependent on program structure.• FmRadio and Life very imprecise. Loops iterating over par

statement(s) multiple times. Over-estimations accumulate.• Matrix quite precise. Executes in one global tick. Thus, thread

WCRT assumption is valid.

1 2 3 40

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

FmRadio

Cores

1 2 3 4 5 6 70

1,000

2,000

3,000

4,000

5,000

6,000

7,000

Fly by Wire

Cores

1 2 3 4 5 6 7 80

20,000

40,000

60,000

80,000

100,000

120,000

140,000

Life

Cores1 2 3 4 5 6 7 8

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

Matrix

Observed

Reachability

MaxPlus

Cores

72

Results

• Our tool generates a timed execution trace for the computed WCRT:– For each core: Thread start/end time, context-

switching, fork/join, ...– Can be used to tune the thread distribution.• Was used to manually find good thread distributions for

each benchmark program.

Outline


Conclusions

• ForeC language for deterministic parallel programming of embedded multicores.

• Based on the synchronous framework, but amenable to parallel execution.

• Can achieve WCRT speedup while providing time-predictability.

• Very precise and fast timing analysis for parallel programs using reachability.

Future work

• Complete the formal semantics of ForeC.

Thread distribution

ForeCsource code

CCFG

Static scheduling

Compiled program

CCFG with assembly

Architecture model

ReachabilityComputed

WCRT

Compilation Timing AnalysisProgrammingAutomatic WCRT-aware scheduling.

Cache hierarchy.

Prune additional infeasible paths using value analysis.

76

Questions?

77

Design Patterns

• Point-to-point• Broadcast• Software pipelining• Divide and conquer– Scatter/Gather– Map/Reduce

78

Point-to-pointshared int sum = 0 combine with plus;

void main(void) { par( f(), g() );}

void f(void) { while (1) { sum = comp1(); pause; }}

void g(void) { while (1) { comp2(sum); pause; }}

New value of sum is received in the next global tick.

Combine operation is not required.

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Broadcastshared int sum = 0 combine with plus;

void main(void) { par( f(), g(), g() );}

void f(void) { while (1) { sum = comp1(); pause; }}

void g(void) { while (1) { comp2(sum); pause; }}

Multiple receivers.

Combine operation is not required.

New value of sum is received in the next global tick.

80

Software Pipeliningshared int s1 = 0, s2 = 0 combine with plus;

void main(void) { par( stage1(), stage2(), stage3() );}

void stage1(void) { while (1) { s1 = comp1(); pause; }}void stage2(void) { pause; while (1) { s2 = comp2(s1); pause; }}

Outputs from each stage are buffered.

Use the delayed behaviour of shared variables to buffer each stage.

void stage3(void) { pause; pause; while (1) { comp3(s2); pause; }}

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Fork/Joininput int[1024] image;int edges = 0;

void main(void) { analyse(0, 1023);}

void analyse(int start, int end) { while (1) { edges = 0; for (i = start; i < end; ++i) { ... image[i] ... ; edges++; } pause; }}

Count the number of edges in an image.

Sequential 1

82

Fork/Joininput int[1024] image;shared int edges = 0 combine with plus;

void main(void) { par( analyse(0, 511), analyse(512, 1023) );}


Parallel 1

83

Fork/Joininput int[1024] image;int edges = 0;

void main(void) { analyse(0, 1023);}


Keep a running total of the number of edges in an image.

For the parallel version, it is not as easy as this.

Sequential 2

84




edges = (1+2) + (1+2) = 6

Parallel 2

85




Global Local

analyse(0,511)

analyse(512,1023)

edges = 0

edges = 0edges = 1

edges = 0edges = 2

edges = (1+2) + (1+2) = 6

Parallel 2

86




Global Local

analyse(0,511)

analyse(512,1023)

edges = 0

edges = 3

edges = 0edges = 1

edges = 0edges = 2

edges = (1+2) + (1+2) = 6

Parallel 2

87




Global Local

analyse(0,511)

analyse(512,1023)

edges = 0

edges = 3

edges = 0edges = 1

edges = 0edges = 2

edges = 3edges = 4

edges = 3edges = 5

edges = (1+2) + (1+2) = 6

Parallel 2

88




Global Local

analyse(0,511)

analyse(512,1023)

edges = 0

edges = 3

edges = 0edges = 1

edges = 0edges = 2

edges = 9

edges = 3edges = 4

edges = 3edges = 5

edges = (1+2) + (1+2) = 6

Parallel 2

89




Global Local

analyse(0,511)

analyse(512,1023)

edges = 0

edges = 3

edges = 0edges = 1

edges = 0edges = 2

edges = 9

edges = 3edges = 4

edges = 3edges = 5

edges = (1+2) + (1+2) = 6

We should track the running total separately from the number of new edges.

Parallel 2

90

Fork/Joininput int[1024] image;typedef struct { int total; int new } Edges;shared Edges edges = { .total = 0, .new = 0 } combine with accum;

Edges accum(Edges copy1, Edges copy2) { copy1.total = copy1.total + copy1.new + copy2.new; copy1.new = 0; return copy1;}


void analyse(int start, int end) { while (1) { edges.new = 0; for (i = start; i < end; ++i) { ... image[i] ... ; edges.new++; } pause; }}

edges = (1+2) + (1+2) = 6

Parallel 3

91





edges = (1+2) + (1+2) = 6

Global Local

analyse(0,511)

analyse(512,1023)

edges = { .total=0, .new=0}

edges = { .total=0, .new=0}edges = { .total=0, .new=1}


Parallel 3

92





edges = (1+2) + (1+2) = 6

Global Local

analyse(0,511)

analyse(512,1023)





Parallel 3

93




void analyse(int start, int end) { while (1) { edges.new = 0; for (i = start; i < end; ++i) { ... image[i] ... ; edges.new++; } pause; }} edges = (1+2) + (1+2) = 6

Global Local

analyse(0,511)

analyse(512,1023)







Parallel 3

94




void analyse(int start, int end) { while (1) { edges.new = 0; for (i = start; i < end; ++i) { ... image[i] ... ; edges.new++; } pause; }} edges = (1+2) + (1+2) = 6

Global Local

analyse(0,511)

analyse(512,1023)








Parallel 3

Introduction

• Existing parallel programming solutions.– Shared memory model.• OpenMP, Pthreads• Intel Cilk Plus, Thread Building Blocks• Unified Parallel C, ParC, X10

– Message passing model.• MPI, SHIM

– Provides ways to manage shared resources but not prevent concurrency errors.

[OpenMP] http://openmp.org [Pthreads] https://computing.llnl.gov/tutorials/pthreads/ [X10] http://x10-lang.org/[Intel Cilk Plus] http://software.intel.com/en-us/intel-cilk-plus [Intel Thread Building Blocks] http://threadingbuildingblocks.org/[Unified Parallel C] http://upc.lbl.gov/ [Ben-Asher et al] ParC – An Extension of C for Shared Memory Parallel Processing.[MPI] http://www.mcs.anl.gov/research/projects/mpi/ [SHIM] SHIM: A Language for Hardware/Software Integration.

Introduction

• Deterministic runtime support.– Pthreads• dOS, Grace, Kendo, CoreDet, Dthreads.

– OpenMP• Deterministic OMP

– Concept of logical time.– Each logical time step broken into an execution

and communication phase.

[Bergan et al 2010] Deterministic Process Groups in dOS.[Olszewski et al 2009] Kendo: Efficient Deterministic Multithreading in Software. [Bergan et al 2010] CoreDet: A Compiler and Runtime System for Deterministic Multithreaded Execution.[Liu et al 2011] Dthreads: Efficient Deterministic Multithreading.[Aviram 2012] Deterministic OpenMP.

ForeC Language

• Behaviour of shared variables is similar to:– Intel Cilk+ (Reducers)– Unified Parallel C (Collectives)– DOMP (Workspace consistency)– Grace (Copy-on-write)– Dthreads (Copy-on-write)

parallel programming and timing analysis on embedded multicores eugene yip the university of...

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