/usr/bin/java -Xmx8000000000 -Xss4m -jar ./plugins/org.eclipse.equinox.launcher_1.5.800.v20200727-1323.jar -data @noDefault -ultimatedata ./data -tc ../../../trunk/examples/toolchains/AutomizerCInline.xml --traceabstraction.trace.refinement.strategy FIXED_PREFERENCES --cacsl2boogietranslator.allow.undefined.functions true --traceabstraction.smt.solver External_ModelsAndUnsatCoreMode --traceabstraction.command.for.external.solver 'cvc4 --incremental --print-success --lang smt' -s ../../../trunk/examples/settings/default/automizer/svcomp-Reach-32bit-Automizer_Bitvector.epf -i ../../../trunk/examples/svcomp/hardness-nfm22/hardness_floatingpointinfluence_no-floats_file-43.i -------------------------------------------------------------------------------- This is Ultimate 0.2.5-dev-b75d321-m [2024-11-03 00:46:05,309 INFO L188 SettingsManager]: Resetting all preferences to default values... [2024-11-03 00:46:05,357 INFO L114 SettingsManager]: Loading settings from /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/../../../trunk/examples/settings/default/automizer/svcomp-Reach-32bit-Automizer_Bitvector.epf [2024-11-03 00:46:05,364 WARN L101 SettingsManager]: Preference file contains the following unknown settings: [2024-11-03 00:46:05,364 WARN L103 SettingsManager]: * de.uni_freiburg.informatik.ultimate.core.Log level for class [2024-11-03 00:46:05,387 INFO L130 SettingsManager]: Preferences different from defaults after loading the file: [2024-11-03 00:46:05,389 INFO L151 SettingsManager]: Preferences of UltimateCore differ from their defaults: [2024-11-03 00:46:05,389 INFO L153 SettingsManager]: * Log level for class=de.uni_freiburg.informatik.ultimate.lib.smtlibutils.quantifier.QuantifierPusher=ERROR; [2024-11-03 00:46:05,390 INFO L151 SettingsManager]: Preferences of Boogie Preprocessor differ from their defaults: [2024-11-03 00:46:05,393 INFO L153 SettingsManager]: * Use memory slicer=true [2024-11-03 00:46:05,393 INFO L151 SettingsManager]: Preferences of Boogie Procedure Inliner differ from their defaults: [2024-11-03 00:46:05,393 INFO L153 SettingsManager]: * Ignore calls to procedures called more than once=ONLY_FOR_SEQUENTIAL_PROGRAMS [2024-11-03 00:46:05,393 INFO L151 SettingsManager]: Preferences of BlockEncodingV2 differ from their defaults: [2024-11-03 00:46:05,394 INFO L153 SettingsManager]: * Create parallel compositions if possible=false [2024-11-03 00:46:05,394 INFO L153 SettingsManager]: * Use SBE=true [2024-11-03 00:46:05,394 INFO L151 SettingsManager]: Preferences of CACSL2BoogieTranslator differ from their defaults: [2024-11-03 00:46:05,394 INFO L153 SettingsManager]: * Pointer base address is valid at dereference=IGNORE [2024-11-03 00:46:05,394 INFO L153 SettingsManager]: * sizeof long=4 [2024-11-03 00:46:05,395 INFO L153 SettingsManager]: * sizeof POINTER=4 [2024-11-03 00:46:05,395 INFO L153 SettingsManager]: * Check division by zero=IGNORE [2024-11-03 00:46:05,396 INFO L153 SettingsManager]: * Pointer to allocated memory at dereference=IGNORE [2024-11-03 00:46:05,397 INFO L153 SettingsManager]: * If two pointers are subtracted or compared they have the same base address=IGNORE [2024-11-03 00:46:05,397 INFO L153 SettingsManager]: * Check array bounds for arrays that are off heap=IGNORE [2024-11-03 00:46:05,398 INFO L153 SettingsManager]: * Adapt memory model on pointer casts if necessary=true [2024-11-03 00:46:05,398 INFO L153 SettingsManager]: * Use bitvectors instead of ints=true [2024-11-03 00:46:05,398 INFO L153 SettingsManager]: * Allow undefined functions=false [2024-11-03 00:46:05,398 INFO L153 SettingsManager]: * Memory model=HoenickeLindenmann_4ByteResolution [2024-11-03 00:46:05,398 INFO L153 SettingsManager]: * sizeof long double=12 [2024-11-03 00:46:05,398 INFO L153 SettingsManager]: * Check if freed pointer was valid=false [2024-11-03 00:46:05,399 INFO L153 SettingsManager]: * Use constant arrays=true [2024-11-03 00:46:05,399 INFO L151 SettingsManager]: Preferences of RCFGBuilder differ from their defaults: [2024-11-03 00:46:05,399 INFO L153 SettingsManager]: * Size of a code block=SequenceOfStatements [2024-11-03 00:46:05,399 INFO L153 SettingsManager]: * Only consider context switches at boundaries of atomic blocks=true [2024-11-03 00:46:05,399 INFO L153 SettingsManager]: * SMT solver=External_DefaultMode [2024-11-03 00:46:05,400 INFO L153 SettingsManager]: * Command for external solver=z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in -t:4000 [2024-11-03 00:46:05,400 INFO L151 SettingsManager]: Preferences of TraceAbstraction differ from their defaults: [2024-11-03 00:46:05,400 INFO L153 SettingsManager]: * Compute Interpolants along a Counterexample=FPandBP [2024-11-03 00:46:05,400 INFO L153 SettingsManager]: * Positions where we compute the Hoare Annotation=LoopHeads [2024-11-03 00:46:05,400 INFO L153 SettingsManager]: * Trace refinement strategy=WOLF [2024-11-03 00:46:05,401 INFO L153 SettingsManager]: * Command for external solver=cvc4 --incremental --print-success --lang smt [2024-11-03 00:46:05,401 INFO L153 SettingsManager]: * Apply one-shot large block encoding in concurrent analysis=false [2024-11-03 00:46:05,401 INFO L153 SettingsManager]: * Automaton type used in concurrency analysis=PETRI_NET [2024-11-03 00:46:05,401 INFO L153 SettingsManager]: * Order on configurations for Petri net unfoldings=DBO [2024-11-03 00:46:05,402 INFO L153 SettingsManager]: * SMT solver=External_ModelsAndUnsatCoreMode [2024-11-03 00:46:05,402 INFO L153 SettingsManager]: * Looper check in Petri net analysis=SEMANTIC WARNING: An illegal reflective access operation has occurred WARNING: Illegal reflective access by com.sun.xml.bind.v2.runtime.reflect.opt.Injector$1 (file:/storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/plugins/com.sun.xml.bind_2.2.0.v201505121915.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int) WARNING: Please consider reporting this to the maintainers of com.sun.xml.bind.v2.runtime.reflect.opt.Injector$1 WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations WARNING: All illegal access operations will be denied in a future release Applying setting for plugin de.uni_freiburg.informatik.ultimate.plugins.generator.traceabstraction: Trace refinement strategy -> FIXED_PREFERENCES Applying setting for plugin de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator: Allow undefined functions -> true Applying setting for plugin de.uni_freiburg.informatik.ultimate.plugins.generator.traceabstraction: SMT solver -> External_ModelsAndUnsatCoreMode Applying setting for plugin de.uni_freiburg.informatik.ultimate.plugins.generator.traceabstraction: Command for external solver -> cvc4 --incremental --print-success --lang smt [2024-11-03 00:46:05,580 INFO L75 nceAwareModelManager]: Repository-Root is: /tmp [2024-11-03 00:46:05,603 INFO L261 ainManager$Toolchain]: [Toolchain 1]: Applicable parser(s) successfully (re)initialized [2024-11-03 00:46:05,607 INFO L217 ainManager$Toolchain]: [Toolchain 1]: Toolchain selected. [2024-11-03 00:46:05,608 INFO L270 PluginConnector]: Initializing CDTParser... [2024-11-03 00:46:05,608 INFO L274 PluginConnector]: CDTParser initialized [2024-11-03 00:46:05,609 INFO L431 ainManager$Toolchain]: [Toolchain 1]: Parsing single file: /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/../../../trunk/examples/svcomp/hardness-nfm22/hardness_floatingpointinfluence_no-floats_file-43.i [2024-11-03 00:46:06,992 INFO L533 CDTParser]: Created temporary CDT project at NULL [2024-11-03 00:46:07,180 INFO L384 CDTParser]: Found 1 translation units. [2024-11-03 00:46:07,180 INFO L180 CDTParser]: Scanning /storage/repos/ultimate/trunk/examples/svcomp/hardness-nfm22/hardness_floatingpointinfluence_no-floats_file-43.i [2024-11-03 00:46:07,186 INFO L427 CDTParser]: About to delete temporary CDT project at /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/0de559040/87b8a6f38f2d40629f3e4f596fc5a6c9/FLAGc74925d62 [2024-11-03 00:46:07,201 INFO L435 CDTParser]: Successfully deleted /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/0de559040/87b8a6f38f2d40629f3e4f596fc5a6c9 [2024-11-03 00:46:07,203 INFO L299 ainManager$Toolchain]: ####################### [Toolchain 1] ####################### [2024-11-03 00:46:07,204 INFO L133 ToolchainWalker]: Walking toolchain with 5 elements. [2024-11-03 00:46:07,205 INFO L112 PluginConnector]: ------------------------CACSL2BoogieTranslator---------------------------- [2024-11-03 00:46:07,205 INFO L270 PluginConnector]: Initializing CACSL2BoogieTranslator... [2024-11-03 00:46:07,210 INFO L274 PluginConnector]: CACSL2BoogieTranslator initialized [2024-11-03 00:46:07,210 INFO L184 PluginConnector]: Executing the observer ACSLObjectContainerObserver from plugin CACSL2BoogieTranslator for "CDTParser AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,211 INFO L204 PluginConnector]: Invalid model from CACSL2BoogieTranslator for observer de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator.ACSLObjectContainerObserver@7315209e and model type de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07, skipping insertion in model container [2024-11-03 00:46:07,211 INFO L184 PluginConnector]: Executing the observer CACSL2BoogieTranslatorObserver from plugin CACSL2BoogieTranslator for "CDTParser AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,233 INFO L175 MainTranslator]: Built tables and reachable declarations [2024-11-03 00:46:07,367 WARN L250 ndardFunctionHandler]: Function reach_error is already implemented but we override the implementation for the call at /storage/repos/ultimate/trunk/examples/svcomp/hardness-nfm22/hardness_floatingpointinfluence_no-floats_file-43.i[916,929] [2024-11-03 00:46:07,409 INFO L210 PostProcessor]: Analyzing one entry point: main [2024-11-03 00:46:07,419 INFO L200 MainTranslator]: Completed pre-run [2024-11-03 00:46:07,428 WARN L250 ndardFunctionHandler]: Function reach_error is already implemented but we override the implementation for the call at /storage/repos/ultimate/trunk/examples/svcomp/hardness-nfm22/hardness_floatingpointinfluence_no-floats_file-43.i[916,929] [2024-11-03 00:46:07,450 INFO L210 PostProcessor]: Analyzing one entry point: main [2024-11-03 00:46:07,471 INFO L204 MainTranslator]: Completed translation [2024-11-03 00:46:07,471 INFO L201 PluginConnector]: Adding new model de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07 WrapperNode [2024-11-03 00:46:07,472 INFO L131 PluginConnector]: ------------------------ END CACSL2BoogieTranslator---------------------------- [2024-11-03 00:46:07,472 INFO L112 PluginConnector]: ------------------------Boogie Procedure Inliner---------------------------- [2024-11-03 00:46:07,473 INFO L270 PluginConnector]: Initializing Boogie Procedure Inliner... [2024-11-03 00:46:07,473 INFO L274 PluginConnector]: Boogie Procedure Inliner initialized [2024-11-03 00:46:07,479 INFO L184 PluginConnector]: Executing the observer TypeChecker from plugin Boogie Procedure Inliner for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,486 INFO L184 PluginConnector]: Executing the observer Inliner from plugin Boogie Procedure Inliner for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,507 INFO L138 Inliner]: procedures = 27, calls = 37, calls flagged for inlining = 8, calls inlined = 8, statements flattened = 130 [2024-11-03 00:46:07,507 INFO L131 PluginConnector]: ------------------------ END Boogie Procedure Inliner---------------------------- [2024-11-03 00:46:07,508 INFO L112 PluginConnector]: ------------------------Boogie Preprocessor---------------------------- [2024-11-03 00:46:07,509 INFO L270 PluginConnector]: Initializing Boogie Preprocessor... [2024-11-03 00:46:07,509 INFO L274 PluginConnector]: Boogie Preprocessor initialized [2024-11-03 00:46:07,518 INFO L184 PluginConnector]: Executing the observer EnsureBoogieModelObserver from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,518 INFO L184 PluginConnector]: Executing the observer TypeChecker from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,521 INFO L184 PluginConnector]: Executing the observer MemorySlicer from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,529 INFO L175 MemorySlicer]: Split 2 memory accesses to 1 slices as follows [2]. 100 percent of accesses are in the largest equivalence class. The 2 initializations are split as follows [2]. The 0 writes are split as follows [0]. [2024-11-03 00:46:07,529 INFO L184 PluginConnector]: Executing the observer ConstExpander from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,529 INFO L184 PluginConnector]: Executing the observer StructExpander from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,535 INFO L184 PluginConnector]: Executing the observer UnstructureCode from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,537 INFO L184 PluginConnector]: Executing the observer FunctionInliner from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,538 INFO L184 PluginConnector]: Executing the observer LTLStepAnnotator from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,539 INFO L184 PluginConnector]: Executing the observer BoogieSymbolTableConstructor from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,541 INFO L131 PluginConnector]: ------------------------ END Boogie Preprocessor---------------------------- [2024-11-03 00:46:07,542 INFO L112 PluginConnector]: ------------------------RCFGBuilder---------------------------- [2024-11-03 00:46:07,542 INFO L270 PluginConnector]: Initializing RCFGBuilder... [2024-11-03 00:46:07,542 INFO L274 PluginConnector]: RCFGBuilder initialized [2024-11-03 00:46:07,543 INFO L184 PluginConnector]: Executing the observer RCFGBuilderObserver from plugin RCFGBuilder for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (1/1) ... [2024-11-03 00:46:07,547 INFO L173 SolverBuilder]: Constructing external solver with command: z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in -t:4000 [2024-11-03 00:46:07,555 INFO L189 MonitoredProcess]: No working directory specified, using /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/z3 [2024-11-03 00:46:07,565 INFO L229 MonitoredProcess]: Starting monitored process 1 with /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in -t:4000 (exit command is (exit), workingDir is null) [2024-11-03 00:46:07,567 INFO L327 MonitoredProcess]: [MP /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/z3 SMTLIB2_COMPLIANT=true -memory:2024 -smt2 -in -t:4000 (1)] Waiting until timeout for monitored process [2024-11-03 00:46:07,586 INFO L130 BoogieDeclarations]: Found specification of procedure #Ultimate.allocInit [2024-11-03 00:46:07,586 INFO L130 BoogieDeclarations]: Found specification of procedure write~init~intINTTYPE1#0 [2024-11-03 00:46:07,587 INFO L130 BoogieDeclarations]: Found specification of procedure assume_abort_if_not [2024-11-03 00:46:07,587 INFO L138 BoogieDeclarations]: Found implementation of procedure assume_abort_if_not [2024-11-03 00:46:07,587 INFO L130 BoogieDeclarations]: Found specification of procedure ULTIMATE.start [2024-11-03 00:46:07,587 INFO L138 BoogieDeclarations]: Found implementation of procedure ULTIMATE.start [2024-11-03 00:46:07,649 INFO L238 CfgBuilder]: Building ICFG [2024-11-03 00:46:07,650 INFO L264 CfgBuilder]: Building CFG for each procedure with an implementation [2024-11-03 00:46:07,883 INFO L? ?]: Removed 14 outVars from TransFormulas that were not future-live. [2024-11-03 00:46:07,883 INFO L287 CfgBuilder]: Performing block encoding [2024-11-03 00:46:07,896 INFO L311 CfgBuilder]: Using the 1 location(s) as analysis (start of procedure ULTIMATE.start) [2024-11-03 00:46:07,896 INFO L316 CfgBuilder]: Removed 1 assume(true) statements. [2024-11-03 00:46:07,897 INFO L201 PluginConnector]: Adding new model de.uni_freiburg.informatik.ultimate.plugins.generator.rcfgbuilder CFG 03.11 12:46:07 BoogieIcfgContainer [2024-11-03 00:46:07,897 INFO L131 PluginConnector]: ------------------------ END RCFGBuilder---------------------------- [2024-11-03 00:46:07,899 INFO L112 PluginConnector]: ------------------------TraceAbstraction---------------------------- [2024-11-03 00:46:07,899 INFO L270 PluginConnector]: Initializing TraceAbstraction... [2024-11-03 00:46:07,901 INFO L274 PluginConnector]: TraceAbstraction initialized [2024-11-03 00:46:07,902 INFO L184 PluginConnector]: Executing the observer TraceAbstractionObserver from plugin TraceAbstraction for "CDTParser AST 03.11 12:46:07" (1/3) ... [2024-11-03 00:46:07,902 INFO L204 PluginConnector]: Invalid model from TraceAbstraction for observer de.uni_freiburg.informatik.ultimate.plugins.generator.traceabstraction.TraceAbstractionObserver@5060f8f6 and model type de.uni_freiburg.informatik.ultimate.plugins.generator.traceabstraction AST 03.11 12:46:07, skipping insertion in model container [2024-11-03 00:46:07,902 INFO L184 PluginConnector]: Executing the observer TraceAbstractionObserver from plugin TraceAbstraction for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 03.11 12:46:07" (2/3) ... [2024-11-03 00:46:07,902 INFO L204 PluginConnector]: Invalid model from TraceAbstraction for observer de.uni_freiburg.informatik.ultimate.plugins.generator.traceabstraction.TraceAbstractionObserver@5060f8f6 and model type de.uni_freiburg.informatik.ultimate.plugins.generator.traceabstraction AST 03.11 12:46:07, skipping insertion in model container [2024-11-03 00:46:07,903 INFO L184 PluginConnector]: Executing the observer TraceAbstractionObserver from plugin TraceAbstraction for "de.uni_freiburg.informatik.ultimate.plugins.generator.rcfgbuilder CFG 03.11 12:46:07" (3/3) ... [2024-11-03 00:46:07,904 INFO L112 eAbstractionObserver]: Analyzing ICFG hardness_floatingpointinfluence_no-floats_file-43.i [2024-11-03 00:46:07,923 INFO L214 ceAbstractionStarter]: Automizer settings: Hoare:LoopHeads NWA Interpolation:FPandBP Determinization: PREDICATE_ABSTRACTION [2024-11-03 00:46:07,923 INFO L154 ceAbstractionStarter]: Applying trace abstraction to program that has 1 error locations. [2024-11-03 00:46:08,012 INFO L332 AbstractCegarLoop]: ======== Iteration 0 == of CEGAR loop == AllErrorsAtOnce ======== [2024-11-03 00:46:08,018 INFO L333 AbstractCegarLoop]: Settings: SEPARATE_VIOLATION_CHECK=true, mInterprocedural=true, mMaxIterations=1000000, mWatchIteration=1000000, mArtifact=RCFG, mInterpolation=FPandBP, mInterpolantAutomaton=STRAIGHT_LINE, mDumpAutomata=false, mAutomataFormat=ATS_NUMERATE, mDumpPath=., mDeterminiation=PREDICATE_ABSTRACTION, mMinimize=MINIMIZE_SEVPA, mAutomataTypeConcurrency=PETRI_NET, mHoareTripleChecks=INCREMENTAL, mHoareAnnotationPositions=LoopHeads, mDumpOnlyReuseAutomata=false, mLimitTraceHistogram=0, mErrorLocTimeLimit=0, mLimitPathProgramCount=0, mCollectInterpolantStatistics=true, mHeuristicEmptinessCheck=false, mHeuristicEmptinessCheckAStarHeuristic=ZERO, mHeuristicEmptinessCheckAStarHeuristicRandomSeed=1337, mHeuristicEmptinessCheckSmtFeatureScoringMethod=DAGSIZE, mSMTFeatureExtraction=false, mSMTFeatureExtractionDumpPath=., mOverrideInterpolantAutomaton=false, mMcrInterpolantMethod=WP, mPorIndependenceSettings=[Lde.uni_freiburg.informatik.ultimate.lib.tracecheckerutils.partialorder.independence.IndependenceSettings;@108e0629, mLbeIndependenceSettings=[IndependenceType=SEMANTIC, AbstractionType=NONE, UseConditional=false, UseSemiCommutativity=true, Solver=Z3, SolverTimeout=1000ms] [2024-11-03 00:46:08,018 INFO L334 AbstractCegarLoop]: Starting to check reachability of 1 error locations. [2024-11-03 00:46:08,022 INFO L276 IsEmpty]: Start isEmpty. Operand has 63 states, 36 states have (on average 1.3055555555555556) internal successors, (47), 37 states have internal predecessors, (47), 24 states have call successors, (24), 1 states have call predecessors, (24), 1 states have return successors, (24), 24 states have call predecessors, (24), 24 states have call successors, (24) [2024-11-03 00:46:08,032 INFO L282 IsEmpty]: Finished isEmpty. Found accepting run of length 148 [2024-11-03 00:46:08,032 INFO L207 NwaCegarLoop]: Found error trace [2024-11-03 00:46:08,033 INFO L215 NwaCegarLoop]: trace histogram [24, 24, 24, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1] [2024-11-03 00:46:08,034 INFO L396 AbstractCegarLoop]: === Iteration 1 === Targeting ULTIMATE.startErr0ASSERT_VIOLATIONERROR_FUNCTION === [ULTIMATE.startErr0ASSERT_VIOLATIONERROR_FUNCTION] === [2024-11-03 00:46:08,037 INFO L157 PredicateUnifier]: Initialized classic predicate unifier [2024-11-03 00:46:08,038 INFO L85 PathProgramCache]: Analyzing trace with hash -791064050, now seen corresponding path program 1 times [2024-11-03 00:46:08,044 INFO L118 FreeRefinementEngine]: Executing refinement strategy FIXED_PREFERENCES [2024-11-03 00:46:08,044 INFO L334 FreeRefinementEngine]: Using trace check IpTcStrategyModulePreferences [1035682151] [2024-11-03 00:46:08,044 INFO L95 rtionOrderModulation]: Keeping assertion order NOT_INCREMENTALLY [2024-11-03 00:46:08,046 INFO L173 SolverBuilder]: Constructing external solver with command: cvc4 --incremental --print-success --lang smt [2024-11-03 00:46:08,046 INFO L189 MonitoredProcess]: No working directory specified, using /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 [2024-11-03 00:46:08,048 INFO L229 MonitoredProcess]: Starting monitored process 2 with /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt (exit command is (exit), workingDir is null) [2024-11-03 00:46:08,049 INFO L327 MonitoredProcess]: [MP /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt (2)] Waiting until timeout for monitored process [2024-11-03 00:46:08,188 INFO L136 AnnotateAndAsserter]: Conjunction of SSA is unsat [2024-11-03 00:46:08,191 INFO L255 TraceCheckSpWp]: Trace formula consists of 233 conjuncts, 1 conjuncts are in the unsatisfiable core [2024-11-03 00:46:08,203 INFO L278 TraceCheckSpWp]: Computing forward predicates... [2024-11-03 00:46:08,262 INFO L134 CoverageAnalysis]: Checked inductivity of 1104 backedges. 46 proven. 0 refuted. 0 times theorem prover too weak. 1058 trivial. 0 not checked. [2024-11-03 00:46:08,263 INFO L311 TraceCheckSpWp]: Computing backward predicates... [2024-11-03 00:46:08,420 INFO L134 CoverageAnalysis]: Checked inductivity of 1104 backedges. 46 proven. 0 refuted. 0 times theorem prover too weak. 1058 trivial. 0 not checked. [2024-11-03 00:46:08,421 INFO L136 FreeRefinementEngine]: Strategy FIXED_PREFERENCES found an infeasible trace [2024-11-03 00:46:08,421 INFO L334 FreeRefinementEngine]: Using interpolant generator IpTcStrategyModulePreferences [1035682151] [2024-11-03 00:46:08,422 INFO L158 FreeRefinementEngine]: IpTcStrategyModulePreferences [1035682151] provided 2 perfect and 0 imperfect interpolant sequences [2024-11-03 00:46:08,422 INFO L185 FreeRefinementEngine]: Found 2 perfect and 0 imperfect interpolant sequences. [2024-11-03 00:46:08,424 INFO L198 FreeRefinementEngine]: Number of different interpolants: perfect sequences [2, 2] imperfect sequences [] total 2 [2024-11-03 00:46:08,425 INFO L121 tionRefinementEngine]: Using interpolant automaton builder IpAbStrategyModuleStraightlineAll [771862879] [2024-11-03 00:46:08,426 INFO L85 oduleStraightlineAll]: Using 2 perfect interpolants to construct interpolant automaton [2024-11-03 00:46:08,431 INFO L548 AbstractCegarLoop]: INTERPOLANT automaton has 2 states [2024-11-03 00:46:08,431 INFO L100 FreeRefinementEngine]: Using predicate unifier PredicateUnifier provided by strategy FIXED_PREFERENCES [2024-11-03 00:46:08,456 INFO L143 InterpolantAutomaton]: Constructing interpolant automaton starting with 2 interpolants. [2024-11-03 00:46:08,456 INFO L145 InterpolantAutomaton]: CoverageRelationStatistics Valid=1, Invalid=1, Unknown=0, NotChecked=0, Total=2 [2024-11-03 00:46:08,458 INFO L87 Difference]: Start difference. First operand has 63 states, 36 states have (on average 1.3055555555555556) internal successors, (47), 37 states have internal predecessors, (47), 24 states have call successors, (24), 1 states have call predecessors, (24), 1 states have return successors, (24), 24 states have call predecessors, (24), 24 states have call successors, (24) Second operand has 2 states, 2 states have (on average 16.0) internal successors, (32), 2 states have internal predecessors, (32), 1 states have call successors, (24), 1 states have call predecessors, (24), 2 states have return successors, (24), 2 states have call predecessors, (24), 1 states have call successors, (24) [2024-11-03 00:46:08,480 INFO L144 Difference]: Subtrahend was deterministic. Have not used determinization. [2024-11-03 00:46:08,481 INFO L93 Difference]: Finished difference Result 119 states and 208 transitions. [2024-11-03 00:46:08,481 INFO L141 InterpolantAutomaton]: Switched to read-only mode: deterministic interpolant automaton has 2 states. [2024-11-03 00:46:08,483 INFO L78 Accepts]: Start accepts. Automaton has has 2 states, 2 states have (on average 16.0) internal successors, (32), 2 states have internal predecessors, (32), 1 states have call successors, (24), 1 states have call predecessors, (24), 2 states have return successors, (24), 2 states have call predecessors, (24), 1 states have call successors, (24) Word has length 147 [2024-11-03 00:46:08,483 INFO L84 Accepts]: Finished accepts. some prefix is accepted. [2024-11-03 00:46:08,489 INFO L225 Difference]: With dead ends: 119 [2024-11-03 00:46:08,489 INFO L226 Difference]: Without dead ends: 59 [2024-11-03 00:46:08,493 INFO L431 NwaCegarLoop]: 0 DeclaredPredicates, 292 GetRequests, 292 SyntacticMatches, 0 SemanticMatches, 0 ConstructedPredicates, 0 IntricatePredicates, 0 DeprecatedPredicates, 0 ImplicationChecksByTransitivity, 0.0s TimeCoverageRelationStatistics Valid=1, Invalid=1, Unknown=0, NotChecked=0, Total=2 [2024-11-03 00:46:08,495 INFO L432 NwaCegarLoop]: 88 mSDtfsCounter, 0 mSDsluCounter, 0 mSDsCounter, 0 mSdLazyCounter, 0 mSolverCounterSat, 0 mSolverCounterUnsat, 0 mSolverCounterUnknown, 0 mSolverCounterNotChecked, 0.0s Time, 0 mProtectedPredicate, 0 mProtectedAction, 0 SdHoareTripleChecker+Valid, 88 SdHoareTripleChecker+Invalid, 0 SdHoareTripleChecker+Unknown, 0 SdHoareTripleChecker+Unchecked, 0.0s SdHoareTripleChecker+Time, 0 IncrementalHoareTripleChecker+Valid, 0 IncrementalHoareTripleChecker+Invalid, 0 IncrementalHoareTripleChecker+Unknown, 0 IncrementalHoareTripleChecker+Unchecked, 0.0s IncrementalHoareTripleChecker+Time [2024-11-03 00:46:08,496 INFO L433 NwaCegarLoop]: SdHoareTripleChecker [0 Valid, 88 Invalid, 0 Unknown, 0 Unchecked, 0.0s Time], IncrementalHoareTripleChecker [0 Valid, 0 Invalid, 0 Unknown, 0 Unchecked, 0.0s Time] [2024-11-03 00:46:08,512 INFO L82 GeneralOperation]: Start minimizeSevpa. Operand 59 states. [2024-11-03 00:46:08,528 INFO L88 GeneralOperation]: Finished minimizeSevpa. Reduced states from 59 to 59. [2024-11-03 00:46:08,530 INFO L82 GeneralOperation]: Start removeUnreachable. Operand has 59 states, 33 states have (on average 1.2121212121212122) internal successors, (40), 33 states have internal predecessors, (40), 24 states have call successors, (24), 1 states have call predecessors, (24), 1 states have return successors, (24), 24 states have call predecessors, (24), 24 states have call successors, (24) [2024-11-03 00:46:08,531 INFO L88 GeneralOperation]: Finished removeUnreachable. Reduced from 59 states to 59 states and 88 transitions. [2024-11-03 00:46:08,532 INFO L78 Accepts]: Start accepts. Automaton has 59 states and 88 transitions. Word has length 147 [2024-11-03 00:46:08,533 INFO L84 Accepts]: Finished accepts. word is rejected. [2024-11-03 00:46:08,533 INFO L471 AbstractCegarLoop]: Abstraction has 59 states and 88 transitions. [2024-11-03 00:46:08,533 INFO L472 AbstractCegarLoop]: INTERPOLANT automaton has has 2 states, 2 states have (on average 16.0) internal successors, (32), 2 states have internal predecessors, (32), 1 states have call successors, (24), 1 states have call predecessors, (24), 2 states have return successors, (24), 2 states have call predecessors, (24), 1 states have call successors, (24) [2024-11-03 00:46:08,533 INFO L276 IsEmpty]: Start isEmpty. Operand 59 states and 88 transitions. [2024-11-03 00:46:08,536 INFO L282 IsEmpty]: Finished isEmpty. Found accepting run of length 148 [2024-11-03 00:46:08,536 INFO L207 NwaCegarLoop]: Found error trace [2024-11-03 00:46:08,536 INFO L215 NwaCegarLoop]: trace histogram [24, 24, 24, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1] [2024-11-03 00:46:08,539 INFO L552 MonitoredProcess]: [MP /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt (2)] Ended with exit code 0 [2024-11-03 00:46:08,737 WARN L453 AbstractCegarLoop]: Destroyed unattended storables created during the last iteration: 2 /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt [2024-11-03 00:46:08,738 INFO L396 AbstractCegarLoop]: === Iteration 2 === Targeting ULTIMATE.startErr0ASSERT_VIOLATIONERROR_FUNCTION === [ULTIMATE.startErr0ASSERT_VIOLATIONERROR_FUNCTION] === [2024-11-03 00:46:08,738 INFO L157 PredicateUnifier]: Initialized classic predicate unifier [2024-11-03 00:46:08,739 INFO L85 PathProgramCache]: Analyzing trace with hash -1986199026, now seen corresponding path program 1 times [2024-11-03 00:46:08,746 INFO L118 FreeRefinementEngine]: Executing refinement strategy FIXED_PREFERENCES [2024-11-03 00:46:08,747 INFO L334 FreeRefinementEngine]: Using trace check IpTcStrategyModulePreferences [439316038] [2024-11-03 00:46:08,747 INFO L95 rtionOrderModulation]: Keeping assertion order NOT_INCREMENTALLY [2024-11-03 00:46:08,747 INFO L173 SolverBuilder]: Constructing external solver with command: cvc4 --incremental --print-success --lang smt [2024-11-03 00:46:08,747 INFO L189 MonitoredProcess]: No working directory specified, using /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 [2024-11-03 00:46:08,748 INFO L229 MonitoredProcess]: Starting monitored process 3 with /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt (exit command is (exit), workingDir is null) [2024-11-03 00:46:08,750 INFO L327 MonitoredProcess]: [MP /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt (3)] Waiting until timeout for monitored process [2024-11-03 00:46:08,982 INFO L136 AnnotateAndAsserter]: Conjunction of SSA is unsat [2024-11-03 00:46:08,985 INFO L255 TraceCheckSpWp]: Trace formula consists of 233 conjuncts, 6 conjuncts are in the unsatisfiable core [2024-11-03 00:46:08,990 INFO L278 TraceCheckSpWp]: Computing forward predicates... [2024-11-03 00:46:09,104 INFO L134 CoverageAnalysis]: Checked inductivity of 1104 backedges. 69 proven. 0 refuted. 0 times theorem prover too weak. 1035 trivial. 0 not checked. [2024-11-03 00:46:09,104 INFO L311 TraceCheckSpWp]: Computing backward predicates... [2024-11-03 00:46:09,278 INFO L134 CoverageAnalysis]: Checked inductivity of 1104 backedges. 69 proven. 0 refuted. 0 times theorem prover too weak. 1035 trivial. 0 not checked. [2024-11-03 00:46:09,279 INFO L136 FreeRefinementEngine]: Strategy FIXED_PREFERENCES found an infeasible trace [2024-11-03 00:46:09,280 INFO L334 FreeRefinementEngine]: Using interpolant generator IpTcStrategyModulePreferences [439316038] [2024-11-03 00:46:09,282 INFO L158 FreeRefinementEngine]: IpTcStrategyModulePreferences [439316038] provided 2 perfect and 0 imperfect interpolant sequences [2024-11-03 00:46:09,282 INFO L185 FreeRefinementEngine]: Found 2 perfect and 0 imperfect interpolant sequences. [2024-11-03 00:46:09,282 INFO L198 FreeRefinementEngine]: Number of different interpolants: perfect sequences [6, 6] imperfect sequences [] total 8 [2024-11-03 00:46:09,283 INFO L121 tionRefinementEngine]: Using interpolant automaton builder IpAbStrategyModuleStraightlineAll [486190164] [2024-11-03 00:46:09,283 INFO L85 oduleStraightlineAll]: Using 2 perfect interpolants to construct interpolant automaton [2024-11-03 00:46:09,284 INFO L548 AbstractCegarLoop]: INTERPOLANT automaton has 8 states [2024-11-03 00:46:09,284 INFO L100 FreeRefinementEngine]: Using predicate unifier PredicateUnifier provided by strategy FIXED_PREFERENCES [2024-11-03 00:46:09,285 INFO L143 InterpolantAutomaton]: Constructing interpolant automaton starting with 8 interpolants. [2024-11-03 00:46:09,285 INFO L145 InterpolantAutomaton]: CoverageRelationStatistics Valid=19, Invalid=37, Unknown=0, NotChecked=0, Total=56 [2024-11-03 00:46:09,286 INFO L87 Difference]: Start difference. First operand 59 states and 88 transitions. Second operand has 8 states, 8 states have (on average 4.5) internal successors, (36), 7 states have internal predecessors, (36), 1 states have call successors, (24), 1 states have call predecessors, (24), 3 states have return successors, (25), 2 states have call predecessors, (25), 1 states have call successors, (25) [2024-11-03 00:46:09,593 INFO L144 Difference]: Subtrahend was deterministic. Have not used determinization. [2024-11-03 00:46:09,593 INFO L93 Difference]: Finished difference Result 123 states and 180 transitions. [2024-11-03 00:46:09,594 INFO L141 InterpolantAutomaton]: Switched to read-only mode: deterministic interpolant automaton has 10 states. [2024-11-03 00:46:09,595 INFO L78 Accepts]: Start accepts. Automaton has has 8 states, 8 states have (on average 4.5) internal successors, (36), 7 states have internal predecessors, (36), 1 states have call successors, (24), 1 states have call predecessors, (24), 3 states have return successors, (25), 2 states have call predecessors, (25), 1 states have call successors, (25) Word has length 147 [2024-11-03 00:46:09,595 INFO L84 Accepts]: Finished accepts. some prefix is accepted. [2024-11-03 00:46:09,596 INFO L225 Difference]: With dead ends: 123 [2024-11-03 00:46:09,596 INFO L226 Difference]: Without dead ends: 67 [2024-11-03 00:46:09,597 INFO L431 NwaCegarLoop]: 0 DeclaredPredicates, 300 GetRequests, 286 SyntacticMatches, 1 SemanticMatches, 13 ConstructedPredicates, 0 IntricatePredicates, 0 DeprecatedPredicates, 17 ImplicationChecksByTransitivity, 0.1s TimeCoverageRelationStatistics Valid=77, Invalid=133, Unknown=0, NotChecked=0, Total=210 [2024-11-03 00:46:09,598 INFO L432 NwaCegarLoop]: 56 mSDtfsCounter, 115 mSDsluCounter, 64 mSDsCounter, 0 mSdLazyCounter, 138 mSolverCounterSat, 137 mSolverCounterUnsat, 0 mSolverCounterUnknown, 0 mSolverCounterNotChecked, 0.2s Time, 0 mProtectedPredicate, 0 mProtectedAction, 117 SdHoareTripleChecker+Valid, 120 SdHoareTripleChecker+Invalid, 275 SdHoareTripleChecker+Unknown, 0 SdHoareTripleChecker+Unchecked, 0.0s SdHoareTripleChecker+Time, 137 IncrementalHoareTripleChecker+Valid, 138 IncrementalHoareTripleChecker+Invalid, 0 IncrementalHoareTripleChecker+Unknown, 0 IncrementalHoareTripleChecker+Unchecked, 0.2s IncrementalHoareTripleChecker+Time [2024-11-03 00:46:09,598 INFO L433 NwaCegarLoop]: SdHoareTripleChecker [117 Valid, 120 Invalid, 275 Unknown, 0 Unchecked, 0.0s Time], IncrementalHoareTripleChecker [137 Valid, 138 Invalid, 0 Unknown, 0 Unchecked, 0.2s Time] [2024-11-03 00:46:09,599 INFO L82 GeneralOperation]: Start minimizeSevpa. Operand 67 states. [2024-11-03 00:46:09,607 INFO L88 GeneralOperation]: Finished minimizeSevpa. Reduced states from 67 to 63. [2024-11-03 00:46:09,607 INFO L82 GeneralOperation]: Start removeUnreachable. Operand has 63 states, 36 states have (on average 1.1388888888888888) internal successors, (41), 36 states have internal predecessors, (41), 24 states have call successors, (24), 2 states have call predecessors, (24), 2 states have return successors, (24), 24 states have call predecessors, (24), 24 states have call successors, (24) [2024-11-03 00:46:09,608 INFO L88 GeneralOperation]: Finished removeUnreachable. Reduced from 63 states to 63 states and 89 transitions. [2024-11-03 00:46:09,609 INFO L78 Accepts]: Start accepts. Automaton has 63 states and 89 transitions. Word has length 147 [2024-11-03 00:46:09,609 INFO L84 Accepts]: Finished accepts. word is rejected. [2024-11-03 00:46:09,609 INFO L471 AbstractCegarLoop]: Abstraction has 63 states and 89 transitions. [2024-11-03 00:46:09,610 INFO L472 AbstractCegarLoop]: INTERPOLANT automaton has has 8 states, 8 states have (on average 4.5) internal successors, (36), 7 states have internal predecessors, (36), 1 states have call successors, (24), 1 states have call predecessors, (24), 3 states have return successors, (25), 2 states have call predecessors, (25), 1 states have call successors, (25) [2024-11-03 00:46:09,610 INFO L276 IsEmpty]: Start isEmpty. Operand 63 states and 89 transitions. [2024-11-03 00:46:09,611 INFO L282 IsEmpty]: Finished isEmpty. Found accepting run of length 148 [2024-11-03 00:46:09,611 INFO L207 NwaCegarLoop]: Found error trace [2024-11-03 00:46:09,611 INFO L215 NwaCegarLoop]: trace histogram [24, 24, 24, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1] [2024-11-03 00:46:09,617 INFO L552 MonitoredProcess]: [MP /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt (3)] Ended with exit code 0 [2024-11-03 00:46:09,812 WARN L453 AbstractCegarLoop]: Destroyed unattended storables created during the last iteration: 3 /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt [2024-11-03 00:46:09,812 INFO L396 AbstractCegarLoop]: === Iteration 3 === Targeting ULTIMATE.startErr0ASSERT_VIOLATIONERROR_FUNCTION === [ULTIMATE.startErr0ASSERT_VIOLATIONERROR_FUNCTION] === [2024-11-03 00:46:09,813 INFO L157 PredicateUnifier]: Initialized classic predicate unifier [2024-11-03 00:46:09,813 INFO L85 PathProgramCache]: Analyzing trace with hash -1928940724, now seen corresponding path program 1 times [2024-11-03 00:46:09,813 INFO L118 FreeRefinementEngine]: Executing refinement strategy FIXED_PREFERENCES [2024-11-03 00:46:09,813 INFO L334 FreeRefinementEngine]: Using trace check IpTcStrategyModulePreferences [1024232421] [2024-11-03 00:46:09,813 INFO L95 rtionOrderModulation]: Keeping assertion order NOT_INCREMENTALLY [2024-11-03 00:46:09,814 INFO L173 SolverBuilder]: Constructing external solver with command: cvc4 --incremental --print-success --lang smt [2024-11-03 00:46:09,814 INFO L189 MonitoredProcess]: No working directory specified, using /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 [2024-11-03 00:46:09,818 INFO L229 MonitoredProcess]: Starting monitored process 4 with /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt (exit command is (exit), workingDir is null) [2024-11-03 00:46:09,822 INFO L327 MonitoredProcess]: [MP /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/cvc4 --incremental --print-success --lang smt (4)] Waiting until timeout for monitored process [2024-11-03 00:46:10,041 INFO L136 AnnotateAndAsserter]: Conjunction of SSA is unsat [2024-11-03 00:46:10,045 INFO L255 TraceCheckSpWp]: Trace formula consists of 233 conjuncts, 23 conjuncts are in the unsatisfiable core [2024-11-03 00:46:10,051 INFO L278 TraceCheckSpWp]: Computing forward predicates... [2024-11-03 00:47:01,781 INFO L134 CoverageAnalysis]: Checked inductivity of 1104 backedges. 536 proven. 84 refuted. 0 times theorem prover too weak. 484 trivial. 0 not checked. [2024-11-03 00:47:01,781 INFO L311 TraceCheckSpWp]: Computing backward predicates...