Table Of ContentSynthesis Lectures on
Engineering, Science, and Technology
Gennaro S. Rodrigues
Fernanda L. Kastensmidt
Alberto Bosio
Approximate
Computing and its
Impact on Accuracy,
Reliability and
Fault-Tolerance
Synthesis Lectures on Engineering, Science,
and Technology
The focus of this series is general topics, and applications about, and for, engineers
and scientists on a wide array of applications, methods and advances. Most titles cover
subjects such as professional development, education, and study skills, as well as basic
introductory undergraduate material and other topics appropriate for a broader and less
technical audience.
Gennaro S. Rodrigues ·
Fernanda L. Kastensmidt · Alberto Bosio
Approximate Computing
and its Impact on Accuracy,
Reliability
and Fault-Tolerance
GennaroS.Rodrigues FernandaL.Kastensmidt
FederalUniversityofRioGrandedoSul FederalUniversityofRioGrandedoSul
PortoAlegre,RioGrandedoSul,Brazil PortoAlegre,RioGrandedoSul,Brazil
AlbertoBosio
UniversityLyon,ECL,INSALyon,CNRS,
UCBL,CPELyon,INL
Lyon,France
ISSN2690-0300 ISSN2690-0327 (electronic)
SynthesisLecturesonEngineering,Science,andTechnology
ISBN978-3-031-15716-5 ISBN978-3-031-15717-2 (eBook)
https://doi.org/10.1007/978-3-031-15717-2
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seekit.
—AynRand
Preface
This book presents a study on the reliability of embedded systems when approximate
computing is applied to both the software and hardware layers. It aims to introduce fault
tolerance techniques based on approximate computing and proves that approximate com-
puting can be applied to safety-critical applications. More in detail, the book overviews
approximate computing methods and proposes approximate fault tolerance techniques
appliedtoreconfigurablehardwareandembeddedsoftwaretoensurehighreliabilitylevel
at low computational costs.
Inspired by the trade-off between the improvements provided by approximate com-
puting and the safety-critical system requirements, the book presents an analysis of
the applicability of approximate computing techniques to safety-critical systems. The
proposed techniques are tested under simulation, emulation, and hardware-based fault
injection experiments. Results show that approximate computing algorithms have a par-
ticular behavior, different from traditional ones. In particular, results show that those
approximate fault tolerance techniques are less costly than traditional ones and can
achieve almost the same reliability level.
The scientific works, experiments, and results presented in this book were developed
overaroundfivetosixyearsofresearch.ThemainauthorcompletedhisPh.D.andacted
as a researcher on a number of institutes and projects during that time.
Porto Alegre, Brazil Gennaro S. Rodrigues
Porto Alegre, Brazil Fernanda L. Kastensmidt
Lyon, France Alberto Bosio
vii
Contents
PartI MotivationandIntroduction
1 Introduction ......................................................... 3
1.1 Embedded Systems and Approximation ............................. 3
1.2 Safety-critical Systems ............................................ 4
1.3 Fault Tolerance .................................................. 5
1.4 This Book ....................................................... 7
References ........................................................... 8
2 AnIntroductiontotheApproximateComputingParadigm ............... 11
2.1 Summary ....................................................... 11
2.2 Quality Metrics .................................................. 12
2.3 Approximation Methods .......................................... 14
2.3.1 Types of Approximation .................................... 14
2.3.2 Technological Implementations .............................. 17
2.4 Conclusion ...................................................... 19
References ........................................................... 20
PartII RadiationEffectsandEvaluationMethodologies
3 RadiationEffectsonDigitalDevices .................................... 25
3.1 Summary ....................................................... 25
3.2 Radiation Environment ............................................ 25
3.3 Radiation Effects ................................................. 27
3.3.1 Single Event Effects (SEE) .................................. 28
3.3.2 Total Ionizing Dose (TID) .................................. 32
3.3.3 Displacement Damage (DD) ................................ 33
3.4 Radiation-Induced Soft Errors in Zynq-7000 FPGA ................... 33
3.5 Conclusion ...................................................... 34
References ........................................................... 35
ix
x Contents
4 MethodologiesforTestingandAssessingElectronicandComputing
Systems ............................................................. 37
4.1 Summary ....................................................... 37
4.2 Fault Tolerance Metrics ........................................... 38
4.3 Onboard Fault Injection Emulation on FPGA ........................ 39
4.4 Onboard Fault Injection Emulation on Embedded Processor ........... 40
4.5 Fault Injection Simulation ......................................... 43
4.6 Laser Fault Injection .............................................. 45
4.7 Conclusion ...................................................... 48
References ........................................................... 48
PartIII FaultToleranceandApproximationinPractice
5 EmbeddedSystemsFaultTolerance .................................... 53
5.1 Summary ....................................................... 53
5.2 Fault Tolerance .................................................. 53
5.3 Reliability of Parallel Embedded Software on Multicore Processors ..... 56
5.4 Parallel Fault Tolerance ........................................... 64
5.5 Conclusion ...................................................... 67
References ........................................................... 68
6 ApproximateComputingandFaultTolerance ........................... 71
6.1 Summary ....................................................... 71
6.2 Approximation Methods .......................................... 71
6.2.1 Data Precision Reduction ................................... 72
6.2.2 Successive Approximation .................................. 73
6.2.3 Taylor Series Approximation ................................ 75
6.3 Approximate Fault Tolerance: Discussion and Motivations ............. 79
6.4 Approximate Triple Modular Redundancy (ATMR) ................... 81
6.4.1 Hardware ATMR Based on Data Precision Approximation ...... 81
6.4.2 Software ATMR Based on Successive Approximation
and Loop-Perforation ....................................... 85
6.4.3 Parallel Software ATMR Based on Function Skipping .......... 87
6.5 Parallel Approximate Error Detection (PAED) ....................... 89
6.6 Conclusion ...................................................... 91
References ........................................................... 92
7 ExperimentalAnalysisandDiscussion .................................. 95
7.1 Summary ....................................................... 95
7.2 Approximation Methods .......................................... 96
7.2.1 Taylor Series Approximation ................................ 96
7.2.2 Successive Approximation and Loop-Perforation ............... 100
7.2.3 Behavior and Application Evaluation on Operating Systems ..... 110
Contents xi
7.3 Hardware ATMR ................................................. 114
7.3.1 Random Accumulated Fault Injection ........................ 115
7.3.2 Exhaustive Fault Injection .................................. 117
7.4 Software ATMR ................................................. 118
7.5 PAED .......................................................... 123
References ........................................................... 127
8 FinalConclusionsandRemarks ....................................... 129
8.1 Summary ....................................................... 129
8.2 Approximate Computing .......................................... 129
8.3 Safety-Critical Systems, Reliability, and Approximate Fault
Tolerance ....................................................... 130
8.4 Experimental Results ............................................. 130
