Implementation of a compiler from Pluscal to TLA+ with Tom

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1 Implementation of a compiler from Pluscal to TLA+ with Tom Marc PINHEDE ESIAL-Telecom Nancy 1 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

2 Contents I Pluscal2.0 TLA+ Tools II Personal work Grammars Tree rewriting Code Generation III Situation after the internship Tests Todo 2 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

3 Introduction Location: Loria Team: AlGorille Supervisor: Martin Quinson Task: Rework on a thesis compiler Subject: Compiler form Pluscal2.0 to TLA+ 3 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

4 Introduction Situation: TLA+, a language used to specify a system : Very mathematical specification Permit to use a model-checker But not an easy language to learn, for program designers. Leslie Lamport introduced Pluscal. But it was still not really easy to use. 4 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

5 Pluscal2.0 Syntax close to standard algorithms Procedures can be used Non typed variables Accept processes and hierarchical processes Atomicity for some part of code accepted Embedded TLA+ code 5 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

6 Pluscal2.0 code algorithm Peterson extends Naturals constants numpeers (* Number of processes *) variables lockreq = [id \in Node -> FALSE], turn = 1, (* tie-break variable *) count = 0 (* number of processes holding the lock *) fair process Node[numPeers] definition other == CHOOSE id \in Node : id # self 6 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

7 Pluscal2.0 code begin ncs: try: cs: loop skip; lockreq[self] := TRUE; turn := other; when ~lockreq[other] \/ turn = self; count := count + 1; leave: count := count - 1; lockreq[self] := FALSE; end loop; 7 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

8 Pluscal2.0 code end process; (*No Main process*) (* Assert: at most one process have the lock *) invariant count <= 1 (* Liveness: each requested lock is eventually granted *) temporal \A p \in Node: [] (<> lockreq[p]) (* Instantiating the model for 2 processes *) constants numpeers = 2 8 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

9 TLA+ Set of Actions Action : Guard conditions Variable modifications List of unchanged variables Special actions that ensure liveness properties 9 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

10 Vrai == hr # 13 Faux == hr # 7 10 / 21 ====================================================== Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom TLA+ code MODULE HourClock EXTENDS Naturals VARIABLE hr HCini == hr \in (1..12) HCnxt == hr = IF hr # 12 THEN hr+1 ELSE 1 HC == HCini /\ [][HCnxt]_hr THEOREM HC => []HCini

11 Outils Main tools: Tom: Language extension. Permit easy tree manipulations. Antlr: Automatic Parser/Lexer generator. Others: Text editor, TlaToolbox,Tlc / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

12 Grammars Grammars are divided in two set: one for Pluscal2.0, the other for TLA+ For each set, two grammars. The antlr version and the Tom version. Four files: Antlr grammar for Pluscal2.0 Antlr grammar for TLA+ Gom signature for Pluscal2.0 Gom signature for TLA+ 12 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

13 Tree rewriting Tree rewriting are executed by tom. Two tools: match: Applied on a piece of the tree. strategy: Applied on the whole tree. Exemple: visit LabeledStatement{ /* Add label to any loop statement.*/ Labellisation(EmptyLabel(),Loop(labeledStatementList))-> { } return Labellisation(GivenLabel(OptionString("loop", ConcOption())),Loop(labeledStatementList)); } 13 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

14 Rewriting steps 14 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

15 Code generation Use of a pretty printer Recursive walk of the tree Two output files (.tla et.cfg) Completed step for the actual TLA+ signature 15 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

16 Tests Approach close to the TDD (Test-Driven Development) used. Set of tests, divided in subset, available Tests identify working instructions. Scripted tests with recorded answers. 16 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

17 Test of the whole compiler Implementation of a simple test requiring every steps of the compiler Test accepeted by the model-checker Verification of trivial properties validated 17 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

18 Unfinished parts Semantic control Normalization for some instructions Potential add of a separate step to manage the PC value or Translator completion. Add of new features to the compiler 18 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

19 Conclusion For the compiler: Use of traditional tools and separation of the work in steps to make sources more accessible Completed main process Some steps need to be completed or extended. As a personnal experience: Rewarding intership and good approach of the research world New tools and new way to program discovered Management and teamwork pleasant 19 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

20 Sources Vérification Formelle d Algorithmes Distribués en PlusCal-2 - Sabina AKHTAR Specifying Systems - Leslie Lamport A Pluscal User s Manual - Leslie Lamport 20 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

21 Thanks Thanks to: Martin QUINSON, my intership supervisor, for his presence and control, but also for the good atmosphere he was able to create in the team. Stephan MERTZ, for helping me to understand the potential of this project. Jean-Christophe BACH, for his help and patience with Tom. 21 / 21 Marc PINHEDE Implementation of a compiler from Pluscal to TLA+ with Tom

TLA+ TLC. Rui Fan Stanislav Funiac Mandana Vaziri. Presented by Spring 2001

TLA+ TLC. Rui Fan Stanislav Funiac Mandana Vaziri. Presented by Spring 2001 TLA+ TLC Presented by Rui Fan Stanislav Funiac Mandana Vaziri 6.897 Spring 2001 Outline Overview of TLA/TLA+ Subset of TLA+ supported by TLC Alternating Bit Protocol example Model checking Demo L. Lamport,