SCCharts. Sequentially Constructive Charts

Transcription

1 SCCharts Sequentially Constructive Charts Reinhard von Hanxleden, Björn Duderstadt, Christian Motika, Steven Smyth, Michael Mendler, Joaquin Aguado, Stephen Mercer, and Owen O Brien Real-Time Systems and Embedded Systems Group Department of Computer Science Christian-Albrechts-Universität zu Kiel, Germany SYNCHRON 13 Dagstuhl, 19 Nov Christian Motika Sequentially Constructive Charts (SCCharts) 1 / 34

2 Motivation Contribution Overview Reactive Embedded Systems Embedded systems react to inputs with computed outputs Typically state based computations Computations often exploit concurrency Threads Threads are problematic Synchronous languages: Lustre, Esterel, SCADE, SyncCharts Christian Motika Sequentially Constructive Charts (SCCharts) 2 / 34

3 Motivation Contribution Overview SyncCharts Statechart dialect for specifying deterministic & robust concurrency SyncCharts: Hierarchy, Concurrency, Broadcast Synchrony Hypothesis 1. Discrete ticks 2. Computations: Zero time Charles André, Semantics of SyncCharts, 2003 [Gerald Lüttgen, 2001] Christian Motika Sequentially Constructive Charts (SCCharts) 3 / 34

4 Motivation Contribution Overview Causality in SyncCharts Christian Motika Sequentially Constructive Charts (SCCharts) 4 / 34

5 Motivation Contribution Overview Causality in SyncCharts (cont d) Rejected by SyncCharts compiler Signal Coherence Rule May seem awkward from SyncCharts perspective, but common paradigm Deterministic sequential execution possible using Sequentially Constructive MoC Sequentially Constructive Charts (SCCharts) Christian Motika Sequentially Constructive Charts (SCCharts) 5 / 34

6 Motivation Contribution Overview Overview SCCharts Overview Normalizing Core SCCharts Implementation in KIELER Demo Christian Motika Sequentially Constructive Charts (SCCharts) 6 / 34

7 Overview Features Core Transformations SCCharts Overview SCCharts = SyncCharts syntax + Seqentially Constructive semantics Hello World of Sequential Constructiveness: ABO Variables instead of signals Behavior (briefly) 1. Initialize 2. Concurrently wait for inputs A or B to become true 3. Once A and B are true after the initial tick, take Termination 4. Sequentially set O1 and O2 Christian Motika Sequentially Constructive Charts (SCCharts) 7 / 34

8 Overview Features Core Transformations SCCharts - Features Christian Motika Sequentially Constructive Charts (SCCharts) 8 / 34

9 Interface declaration Region ID Transition trigger/effect Initial state Transition priority Immediate transition Suspension Connector Count Delay History transition Conditional termination Root state Local declaration Superstate Anonymous simple states Termination Named simple states Final state Signal Entry/During/Exit actions Deferred transition Strong abort Pre-Operator Weak abort

10 Overview Features Core Transformations Motivation Interface declaration Region ID Transition trigger/effect Initial state Transition priority Immediate transition Suspension Connector Count Delay History transition Conditional termination Root state Local declaration Superstate Anonymous simple states Termination Named simple states Final state Signal Entry/During/Exit actions Deferred transition Strong abort Pre-Operator Weak abort Numerous features Readability of models Compilation & verification more complex Various features can be expressed by other ones Syntactic sugar Minimal base language (Core SCCharts) + advanced features (Extended SCCharts) Define extended features by means of base features Extensible Similar to Esterel Kernel Statements & Statement Expansion Christian Motika Sequentially Constructive Charts (SCCharts) 10 / 34

11 Overview Features Core Transformations SCCharts - Core & Extended Features Christian Motika Sequentially Constructive Charts (SCCharts) 11 / 34

12 Overview Features Core Transformations Overview SCCharts Overview Normalizing Core SCCharts Implementation in KIELER Demo Christian Motika Sequentially Constructive Charts (SCCharts) 12 / 34

13 Connector Signal Strong Abort SCCharts - Core Transformations Examples Interface declaration Region ID Transition trigger/effect Initial state Transition priority Immediate transition Suspension Connector Count Delay History transition Conditional termination Root state Local declaration Superstate Anonymous simple states Termination Named simple states Final state Signal Entry/During/Exit actions Deferred transition Strong abort Pre-Operator Weak abort Christian Motika Sequentially Constructive Charts (SCCharts) 13 / 34

14 Connector Signal Strong Abort Transforming Connectors Extended SCCharts with Connectors Core SCCharts without Connectors Christian Motika Sequentially Constructive Charts (SCCharts) 14 / 34

15 Connector Signal Strong Abort Transforming Signals Christian Motika Sequentially Constructive Charts (SCCharts) 15 / 34

16 Connector Signal Strong Abort SyncChart and SCChart ABRO Charles André, Semantics of SyncCharts, ABRO SCChart Christian Motika Sequentially Constructive Charts (SCCharts) 16 / 34

17 Connector Signal Strong Abort ABRO - Transforming Strong Aborts. Core SCChart without Strong Abort ABRO SCChart with Strong Abort Write-Things-Once (WTO) principle violated Christian Motika Sequentially Constructive Charts (SCCharts) 17 / 34

18 Connector Signal Strong Abort ABRO - Transforming Strong Aborts (cont d). Core SCChart without Strong Abort and WTO ABRO SCChart with Strong Abort Christian Motika Sequentially Constructive Charts (SCCharts) 18 / 34

19 Connector Signal Strong Abort Transforming General Aborts Extended SCCharts with Aborts. Core SCCharts with one Termination Christian Motika Sequentially Constructive Charts (SCCharts) 19 / 34

20 Connector Signal Strong Abort Overview SCCharts Overview Normalizing Core SCCharts Implementation in KIELER Demo Christian Motika Sequentially Constructive Charts (SCCharts) 20 / 34

21 Normalization Modeling SCCharts & Demo Conclusion Normalization Further simplify compilation process for Core SCCharts Allowed patterns: Region Superstate Trigger Action State (connected states) (parallel regions) (conditionals) (assignments) (tick boundary) Christian Motika Sequentially Constructive Charts (SCCharts) 21 / 34

22 Normalization Modeling SCCharts & Demo Conclusion Actions Normalization Core SCChart before normalization Core SCChart after normalization Christian Motika Sequentially Constructive Charts (SCCharts) 22 / 34

23 Normalization Modeling SCCharts & Demo Conclusion Actions Normalization (cont d) Core SCChart before normalization Core SCChart after normalization Christian Motika Sequentially Constructive Charts (SCCharts) 23 / 34

24 Normalization Modeling SCCharts & Demo Conclusion Actions Normalization Implementation Example 1 def void transformtriggeractions(transition transition) { 2 if (((transition.trigger!= null!transition.immediate) 3 &&!transition.actions.nullorempty) transition.actions.size > 1) { 4 5 val targetstate = transition.targetstate 6 val parentregion = targetstate.parentregion 7 val transitionoriginaltarget = transition.targetstate 8 9 var Transition lasttransition = transition for (action : transition.actions.immutablecopy) { val actionstate = parentregion.createstate(targetstate.id + action.id) 14 actionstate.settypeconnector val actiontransition = createimmediatetransition.addaction(action) 17 actiontransition.setsourcestate(actionstate) lasttransition.settargetstate(actionstate) 20 lasttransition = actiontransition 21 } lasttransition.settargetstate(transitionoriginaltarget) 24 } 25 } Christian Motika Sequentially Constructive Charts (SCCharts) 24 / 34

25 Normalization Modeling SCCharts & Demo Conclusion Trigger Normalization Core SCChart before normalization Core SCChart after normalization (Surface & Depth) Christian Motika Sequentially Constructive Charts (SCCharts) 25 / 34

26 Normalization Modeling SCCharts & Demo Conclusion Trigger Normalization (Cont d) Core SCChart before normalization Core SCChart after optimized normalization Christian Motika Sequentially Constructive Charts (SCCharts) 26 / 34

27 Normalization Modeling SCCharts & Demo Conclusion ABO - Normalization Example (Actions) ABO Core SCChart. ABO Core SCChart with normalized actions Christian Motika Sequentially Constructive Charts (SCCharts) 27 / 34

28 Normalization Modeling SCCharts & Demo Conclusion ABO - Normalization Example (Actions & Trigger) ABO Core SCChart with normalized actions. ABO Normalized SCChart Christian Motika Sequentially Constructive Charts (SCCharts) 28 / 34

29 Normalization Modeling SCCharts & Demo Conclusion Overview SCCharts Overview Normalizing Core SCCharts Implementation in KIELER Demo Christian Motika Sequentially Constructive Charts (SCCharts) 29 / 34

30 Normalization Modeling SCCharts & Demo Conclusion Textual Modeling with KLighD Eclipse based KIELER framework Textual modeling based on Xtext Syntax highlighting Code completion Formatter Transient view based on KLighD [C. Schneider et al., VL/HCC 13] Christian Motika Sequentially Constructive Charts (SCCharts) 30 / 34

31 Normalization Modeling SCCharts & Demo Conclusion SCCharts Demo LIVE DEMO Christian Motika Sequentially Constructive Charts (SCCharts) 31 / 34

32 Normalization Modeling SCCharts & Demo Conclusion Conclusions SyncCharts are a great choice for specifying deterministic control-flow behavior but does not accept sequentiality If (!done) {... ; done = true;} SCCharts extend SyncCharts w.r.t. semantics Sequentially Constructive MoC All valid SyncCharts interpreted as SCCharts keep their meaning Core SCCharts: Few basic features for simpler & more robust compilation Extended SCCharts: Syntactic sugar, readability, extensible Normalized SCCharts: Further ease compilation Reinhard will give details :-) Christian Motika Sequentially Constructive Charts (SCCharts) 32 / 34

33 Normalization Modeling SCCharts & Demo Conclusion To Go Further CHARLES ANDRÉ. Semantics of SyncCharts, GÉRARD BERRY. The Esterel v5 Language Primer, SCHNEIDER, C., SPÖNEMANN, M., AND VON HANXLEDEN, R. Just model! Putting automatic synthesis of node-link-diagrams into practice. In Proceedings of the IEEE Symposium on Visual Languages and Human-Centric Computing (VL/HCC 13) (San Jose, CA, USA, Sept. 2013). UNI KIEL, REAL-TIME AND EMBEDDED SYSTEMS GROUP. KIELER webpage. VON HANXLEDEN, R., LEE, E. A., MOTIKA, C., AND FUHRMANN, H. Multi-view modeling and pragmatics in 2020 position paper on designing complex cyber-physical systems. In Proceedings of the 17th International Monterey Workshop on Development, Operation and Management of Large-Scale Complex IT Systems, LNCS (Oxford, UK, Dec. 2012), vol VON HANXLEDEN, R., MENDLER, M., AGUADO, J., DUDERSTADT, B., FUHRMANN, I., MOTIKA, C., MERCER, S., AND O BRIEN, O. Sequentially Constructive Concurrency A conservative extension of the synchronous model of computation. Christian In Proc. Motika Design, Automation and Test in Europe Sequentially Conference Constructive (DATE 13) Charts (Grenoble, (SCCharts) France, Mar. 2013), IEEE, 33 / 34

34 Normalization Modeling SCCharts & Demo Conclusion That s all folks! Any questions or suggestions? Christian Motika Sequentially Constructive Charts (SCCharts) 34 / 34

35 Sequentially Constructive MoC Natural sequencing prescribes deterministic scheduling stmt1; stmt2 trigger/effect Only concurrent data dependencies matter Sequential data dependencies do not lead to rejection Deterministic concurrent scheduling: Distinguish between relative and absolute writes Absolute writes: x = false Relative writes: x = x true Reads: y = x (1) Absolute writes, (2) relative writes, (3) reads Sequentially Constructiveness fully subsumes Berry Constructiveness Christian Motika Sequentially Constructive Charts (SCCharts) 35 / 34

36 Concurrency with Threads Typical observer pattern implemented with Java Threads 1 public class ValueHolder { 2 private List listeners = new LinkedList(); 3 private int value; 4 public interface Listener { 5 public void valuechanged(int newvalue); 6 } 7 public void addlistener(listener listener) { 8 listeners.add(listener); 9 } 10 public void setvalue(int newvalue) { 11 value = newvalue; 12 Iterator i = listeners.iterator(); 13 while(i.hasnext()) { 14 ((Listener)i.next()).valueChanged(newValue); 15 } 16 } 17 } E. A. Lee, The Problem with Threads, 2006 Not thread safe! E.g., multiple threads call setvalue(). Christian Motika Sequentially Constructive Charts (SCCharts) 36 / 34

37 Synchronous Program Classes Sequentially Constructive (S) y=x 1 par if (!x 0 ) x 1 =1 if (x) x=1 if (!x) x=1 if (x and y) x=1 if (x) x=1 par if (!y) z=1 par if (!z) {y=1; z=1} Pnueli-Shalev Constructive (P) P P P PS Speculate on absence Berry Constructive (B) if (x) then y=z par Static cycles if (!x) then z=y Dynamic scheduling P S Sequences P of values AS P APS PALPS P LPS P BLPS P ABLPS Ineffective writes P LP if (!x) y=1 par if (!y) {x=1; y=1} P ALS if (x) y=1 par if (y) x=1 else {x=1; y=1} if (x) x=1 else x=1 PLS x 0 =1; {if (x 0 ) then y=1 par if (y) then x 1 =1} Out-of-order scheduling Speculate on absence or presence P L Cycle of concurrent dependencies Logically Correct (L) Acyclic SC (A) or, concurrent writes if (x) x=1 par if (!x) x=1 P 0 if (!x) y=1 par if (!y) x=1 All Programs Christian Motika Sequentially Constructive Charts (SCCharts) 37 / 34