/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/BuchiAutomizerCInline.xml -s ../../../trunk/examples/settings/default/automizer/svcomp-Termination-32bit-Automizer_Default.epf --buchiautomizer.fairness.type.for.concurrent.programs FAIRNESS_INTERSECTION -i ../../../trunk/examples/svcomp/weaver/parallel-parallel-sum-2.wvr.c -------------------------------------------------------------------------------- This is Ultimate 0.2.3-wip.me.fairness-42053ae-m [2023-09-08 14:43:25,013 INFO L172 SettingsManager]: Resetting all preferences to default values... [2023-09-08 14:43:25,081 INFO L100 SettingsManager]: Loading settings from /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/../../../trunk/examples/settings/default/automizer/svcomp-Termination-32bit-Automizer_Default.epf [2023-09-08 14:43:25,118 INFO L114 SettingsManager]: Preferences different from defaults after loading the file: [2023-09-08 14:43:25,119 INFO L135 SettingsManager]: Preferences of UltimateCore differ from their defaults: [2023-09-08 14:43:25,119 INFO L137 SettingsManager]: * Log level for class=de.uni_freiburg.informatik.ultimate.lib.smtlibutils.quantifier.QuantifierPusher=ERROR; [2023-09-08 14:43:25,121 INFO L135 SettingsManager]: Preferences of BlockEncodingV2 differ from their defaults: [2023-09-08 14:43:25,121 INFO L137 SettingsManager]: * Create parallel compositions if possible=false [2023-09-08 14:43:25,122 INFO L137 SettingsManager]: * Use SBE=true [2023-09-08 14:43:25,126 INFO L135 SettingsManager]: Preferences of BuchiAutomizer differ from their defaults: [2023-09-08 14:43:25,126 INFO L137 SettingsManager]: * NCSB implementation=INTSET_LAZY3 [2023-09-08 14:43:25,126 INFO L137 SettingsManager]: * Use old map elimination=false [2023-09-08 14:43:25,127 INFO L137 SettingsManager]: * Use external solver (rank synthesis)=false [2023-09-08 14:43:25,128 INFO L137 SettingsManager]: * Use only trivial implications for array writes=true [2023-09-08 14:43:25,128 INFO L137 SettingsManager]: * Rank analysis=LINEAR_WITH_GUESSES [2023-09-08 14:43:25,128 INFO L135 SettingsManager]: Preferences of CACSL2BoogieTranslator differ from their defaults: [2023-09-08 14:43:25,128 INFO L137 SettingsManager]: * sizeof long=4 [2023-09-08 14:43:25,128 INFO L137 SettingsManager]: * Check unreachability of error function in SV-COMP mode=false [2023-09-08 14:43:25,129 INFO L137 SettingsManager]: * Overapproximate operations on floating types=true [2023-09-08 14:43:25,129 INFO L137 SettingsManager]: * sizeof POINTER=4 [2023-09-08 14:43:25,129 INFO L137 SettingsManager]: * Check division by zero=IGNORE [2023-09-08 14:43:25,129 INFO L137 SettingsManager]: * Pointer to allocated memory at dereference=ASSUME [2023-09-08 14:43:25,130 INFO L137 SettingsManager]: * If two pointers are subtracted or compared they have the same base address=ASSUME [2023-09-08 14:43:25,130 INFO L137 SettingsManager]: * Check array bounds for arrays that are off heap=ASSUME [2023-09-08 14:43:25,130 INFO L137 SettingsManager]: * sizeof long double=12 [2023-09-08 14:43:25,130 INFO L137 SettingsManager]: * Check if freed pointer was valid=false [2023-09-08 14:43:25,130 INFO L137 SettingsManager]: * Assume nondeterminstic values are in range=false [2023-09-08 14:43:25,131 INFO L137 SettingsManager]: * Use constant arrays=true [2023-09-08 14:43:25,131 INFO L137 SettingsManager]: * Pointer base address is valid at dereference=ASSUME [2023-09-08 14:43:25,131 INFO L135 SettingsManager]: Preferences of RCFGBuilder differ from their defaults: [2023-09-08 14:43:25,132 INFO L137 SettingsManager]: * Size of a code block=SequenceOfStatements [2023-09-08 14:43:25,132 INFO L135 SettingsManager]: Preferences of TraceAbstraction differ from their defaults: [2023-09-08 14:43:25,132 INFO L137 SettingsManager]: * Trace refinement strategy=CAMEL [2023-09-08 14:43:25,133 INFO L137 SettingsManager]: * Apply one-shot large block encoding in concurrent analysis=false [2023-09-08 14:43:25,134 INFO L135 SettingsManager]: Preferences of IcfgTransformer differ from their defaults: [2023-09-08 14:43:25,134 INFO L137 SettingsManager]: * TransformationType=MODULO_NEIGHBOR 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$1 WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations WARNING: All illegal access operations will be denied in a future release Applying setting for plugin de.uni_freiburg.informatik.ultimate.plugins.generator.buchiautomizer: Fairness type for concurrent programs -> FAIRNESS_INTERSECTION [2023-09-08 14:43:25,370 INFO L75 nceAwareModelManager]: Repository-Root is: /tmp [2023-09-08 14:43:25,396 INFO L261 ainManager$Toolchain]: [Toolchain 1]: Applicable parser(s) successfully (re)initialized [2023-09-08 14:43:25,399 INFO L217 ainManager$Toolchain]: [Toolchain 1]: Toolchain selected. [2023-09-08 14:43:25,400 INFO L270 PluginConnector]: Initializing CDTParser... [2023-09-08 14:43:25,400 INFO L274 PluginConnector]: CDTParser initialized [2023-09-08 14:43:25,401 INFO L431 ainManager$Toolchain]: [Toolchain 1]: Parsing single file: /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/../../../trunk/examples/svcomp/weaver/parallel-parallel-sum-2.wvr.c [2023-09-08 14:43:26,581 INFO L533 CDTParser]: Created temporary CDT project at NULL [2023-09-08 14:43:26,781 INFO L384 CDTParser]: Found 1 translation units. [2023-09-08 14:43:26,782 INFO L180 CDTParser]: Scanning /storage/repos/ultimate/trunk/examples/svcomp/weaver/parallel-parallel-sum-2.wvr.c [2023-09-08 14:43:26,791 INFO L427 CDTParser]: About to delete temporary CDT project at /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/20ac34e18/d0f5c40e256c40608e707d7c6db709f3/FLAG07f57a064 [2023-09-08 14:43:26,805 INFO L435 CDTParser]: Successfully deleted /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/data/20ac34e18/d0f5c40e256c40608e707d7c6db709f3 [2023-09-08 14:43:26,808 INFO L299 ainManager$Toolchain]: ####################### [Toolchain 1] ####################### [2023-09-08 14:43:26,809 INFO L133 ToolchainWalker]: Walking toolchain with 5 elements. [2023-09-08 14:43:26,810 INFO L112 PluginConnector]: ------------------------CACSL2BoogieTranslator---------------------------- [2023-09-08 14:43:26,811 INFO L270 PluginConnector]: Initializing CACSL2BoogieTranslator... [2023-09-08 14:43:26,814 INFO L274 PluginConnector]: CACSL2BoogieTranslator initialized [2023-09-08 14:43:26,814 INFO L184 PluginConnector]: Executing the observer ACSLObjectContainerObserver from plugin CACSL2BoogieTranslator for "CDTParser AST 08.09 02:43:26" (1/1) ... [2023-09-08 14:43:26,815 INFO L204 PluginConnector]: Invalid model from CACSL2BoogieTranslator for observer de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator.ACSLObjectContainerObserver@55ab7b1 and model type de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:26, skipping insertion in model container [2023-09-08 14:43:26,816 INFO L184 PluginConnector]: Executing the observer CACSL2BoogieTranslatorObserver from plugin CACSL2BoogieTranslator for "CDTParser AST 08.09 02:43:26" (1/1) ... [2023-09-08 14:43:26,822 INFO L145 MainTranslator]: Starting translation in SV-COMP mode [2023-09-08 14:43:26,844 INFO L178 MainTranslator]: Built tables and reachable declarations [2023-09-08 14:43:26,983 WARN L247 ndardFunctionHandler]: Function reach_error is already implemented but we override the implementation for the call at /storage/repos/ultimate/trunk/examples/svcomp/weaver/parallel-parallel-sum-2.wvr.c[4225,4238] [2023-09-08 14:43:26,989 INFO L209 PostProcessor]: Analyzing one entry point: main [2023-09-08 14:43:27,000 INFO L203 MainTranslator]: Completed pre-run [2023-09-08 14:43:27,026 WARN L247 ndardFunctionHandler]: Function reach_error is already implemented but we override the implementation for the call at /storage/repos/ultimate/trunk/examples/svcomp/weaver/parallel-parallel-sum-2.wvr.c[4225,4238] [2023-09-08 14:43:27,030 INFO L209 PostProcessor]: Analyzing one entry point: main [2023-09-08 14:43:27,038 WARN L667 CHandler]: The function __VERIFIER_atomic_begin is called, but not defined or handled by StandardFunctionHandler. [2023-09-08 14:43:27,039 WARN L667 CHandler]: The function __VERIFIER_atomic_end is called, but not defined or handled by StandardFunctionHandler. [2023-09-08 14:43:27,045 INFO L208 MainTranslator]: Completed translation [2023-09-08 14:43:27,046 INFO L201 PluginConnector]: Adding new model de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27 WrapperNode [2023-09-08 14:43:27,046 INFO L131 PluginConnector]: ------------------------ END CACSL2BoogieTranslator---------------------------- [2023-09-08 14:43:27,047 INFO L112 PluginConnector]: ------------------------Boogie Procedure Inliner---------------------------- [2023-09-08 14:43:27,047 INFO L270 PluginConnector]: Initializing Boogie Procedure Inliner... [2023-09-08 14:43:27,048 INFO L274 PluginConnector]: Boogie Procedure Inliner initialized [2023-09-08 14:43:27,058 INFO L184 PluginConnector]: Executing the observer TypeChecker from plugin Boogie Procedure Inliner for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,085 INFO L184 PluginConnector]: Executing the observer Inliner from plugin Boogie Procedure Inliner for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,116 INFO L138 Inliner]: procedures = 29, calls = 88, calls flagged for inlining = 22, calls inlined = 32, statements flattened = 384 [2023-09-08 14:43:27,117 INFO L131 PluginConnector]: ------------------------ END Boogie Procedure Inliner---------------------------- [2023-09-08 14:43:27,118 INFO L112 PluginConnector]: ------------------------Boogie Preprocessor---------------------------- [2023-09-08 14:43:27,118 INFO L270 PluginConnector]: Initializing Boogie Preprocessor... [2023-09-08 14:43:27,118 INFO L274 PluginConnector]: Boogie Preprocessor initialized [2023-09-08 14:43:27,135 INFO L184 PluginConnector]: Executing the observer EnsureBoogieModelObserver from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,136 INFO L184 PluginConnector]: Executing the observer TypeChecker from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,151 INFO L184 PluginConnector]: Executing the observer ConstExpander from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,152 INFO L184 PluginConnector]: Executing the observer StructExpander from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,161 INFO L184 PluginConnector]: Executing the observer UnstructureCode from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,167 INFO L184 PluginConnector]: Executing the observer FunctionInliner from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,170 INFO L184 PluginConnector]: Executing the observer LTLStepAnnotator from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,172 INFO L184 PluginConnector]: Executing the observer BoogieSymbolTableConstructor from plugin Boogie Preprocessor for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,176 INFO L131 PluginConnector]: ------------------------ END Boogie Preprocessor---------------------------- [2023-09-08 14:43:27,177 INFO L112 PluginConnector]: ------------------------RCFGBuilder---------------------------- [2023-09-08 14:43:27,177 INFO L270 PluginConnector]: Initializing RCFGBuilder... [2023-09-08 14:43:27,177 INFO L274 PluginConnector]: RCFGBuilder initialized [2023-09-08 14:43:27,178 INFO L184 PluginConnector]: Executing the observer RCFGBuilderObserver from plugin RCFGBuilder for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (1/1) ... [2023-09-08 14:43:27,183 INFO L173 SolverBuilder]: Constructing external solver with command: z3 SMTLIB2_COMPLIANT=true -memory:1024 -smt2 -in -t:12000 [2023-09-08 14:43:27,194 INFO L189 MonitoredProcess]: No working directory specified, using /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/z3 [2023-09-08 14:43:27,222 INFO L229 MonitoredProcess]: Starting monitored process 1 with /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/z3 SMTLIB2_COMPLIANT=true -memory:1024 -smt2 -in -t:12000 (exit command is (exit), workingDir is null) [2023-09-08 14:43:27,235 INFO L327 MonitoredProcess]: [MP /storage/repos/ultimate/releaseScripts/default/UAutomizer-linux/z3 SMTLIB2_COMPLIANT=true -memory:1024 -smt2 -in -t:12000 (1)] Waiting until timeout for monitored process [2023-09-08 14:43:27,260 INFO L130 BoogieDeclarations]: Found specification of procedure #Ultimate.allocInit [2023-09-08 14:43:27,260 INFO L130 BoogieDeclarations]: Found specification of procedure #Ultimate.allocOnStack [2023-09-08 14:43:27,261 INFO L130 BoogieDeclarations]: Found specification of procedure write~int [2023-09-08 14:43:27,261 INFO L130 BoogieDeclarations]: Found specification of procedure read~int [2023-09-08 14:43:27,261 INFO L130 BoogieDeclarations]: Found specification of procedure thread1 [2023-09-08 14:43:27,261 INFO L138 BoogieDeclarations]: Found implementation of procedure thread1 [2023-09-08 14:43:27,261 INFO L130 BoogieDeclarations]: Found specification of procedure thread2 [2023-09-08 14:43:27,262 INFO L138 BoogieDeclarations]: Found implementation of procedure thread2 [2023-09-08 14:43:27,262 INFO L130 BoogieDeclarations]: Found specification of procedure thread3 [2023-09-08 14:43:27,262 INFO L138 BoogieDeclarations]: Found implementation of procedure thread3 [2023-09-08 14:43:27,262 INFO L130 BoogieDeclarations]: Found specification of procedure thread4 [2023-09-08 14:43:27,262 INFO L138 BoogieDeclarations]: Found implementation of procedure thread4 [2023-09-08 14:43:27,262 INFO L130 BoogieDeclarations]: Found specification of procedure write~init~int [2023-09-08 14:43:27,262 INFO L130 BoogieDeclarations]: Found specification of procedure thread5 [2023-09-08 14:43:27,264 INFO L138 BoogieDeclarations]: Found implementation of procedure thread5 [2023-09-08 14:43:27,264 INFO L130 BoogieDeclarations]: Found specification of procedure thread6 [2023-09-08 14:43:27,265 INFO L138 BoogieDeclarations]: Found implementation of procedure thread6 [2023-09-08 14:43:27,265 INFO L130 BoogieDeclarations]: Found specification of procedure __VERIFIER_atomic_end [2023-09-08 14:43:27,265 INFO L130 BoogieDeclarations]: Found specification of procedure __VERIFIER_atomic_begin [2023-09-08 14:43:27,265 INFO L130 BoogieDeclarations]: Found specification of procedure #Ultimate.allocOnHeap [2023-09-08 14:43:27,265 INFO L130 BoogieDeclarations]: Found specification of procedure ULTIMATE.start [2023-09-08 14:43:27,265 INFO L138 BoogieDeclarations]: Found implementation of procedure ULTIMATE.start [2023-09-08 14:43:27,265 INFO L130 BoogieDeclarations]: Found specification of procedure ULTIMATE.dealloc [2023-09-08 14:43:27,267 WARN L210 CfgBuilder]: User set CodeBlockSize to SequenceOfStatements but program contains fork statements. Overwriting the user preferences and setting CodeBlockSize to OneNontrivialStatement [2023-09-08 14:43:27,374 INFO L236 CfgBuilder]: Building ICFG [2023-09-08 14:43:27,376 INFO L262 CfgBuilder]: Building CFG for each procedure with an implementation [2023-09-08 14:43:27,889 INFO L277 CfgBuilder]: Performing block encoding [2023-09-08 14:43:28,084 INFO L297 CfgBuilder]: Using the 1 location(s) as analysis (start of procedure ULTIMATE.start) [2023-09-08 14:43:28,084 INFO L302 CfgBuilder]: Removed 5 assume(true) statements. [2023-09-08 14:43:28,087 INFO L201 PluginConnector]: Adding new model de.uni_freiburg.informatik.ultimate.plugins.generator.rcfgbuilder CFG 08.09 02:43:28 BoogieIcfgContainer [2023-09-08 14:43:28,087 INFO L131 PluginConnector]: ------------------------ END RCFGBuilder---------------------------- [2023-09-08 14:43:28,088 INFO L112 PluginConnector]: ------------------------BuchiAutomizer---------------------------- [2023-09-08 14:43:28,088 INFO L270 PluginConnector]: Initializing BuchiAutomizer... [2023-09-08 14:43:28,091 INFO L274 PluginConnector]: BuchiAutomizer initialized [2023-09-08 14:43:28,092 INFO L99 BuchiAutomizer]: Safety of program was proven or not checked, starting termination analysis [2023-09-08 14:43:28,092 INFO L184 PluginConnector]: Executing the observer BuchiAutomizerObserver from plugin BuchiAutomizer for "CDTParser AST 08.09 02:43:26" (1/3) ... [2023-09-08 14:43:28,093 INFO L204 PluginConnector]: Invalid model from BuchiAutomizer for observer de.uni_freiburg.informatik.ultimate.plugins.generator.buchiautomizer.BuchiAutomizerObserver@4c503e03 and model type de.uni_freiburg.informatik.ultimate.plugins.generator.buchiautomizer AST 08.09 02:43:28, skipping insertion in model container [2023-09-08 14:43:28,093 INFO L99 BuchiAutomizer]: Safety of program was proven or not checked, starting termination analysis [2023-09-08 14:43:28,093 INFO L184 PluginConnector]: Executing the observer BuchiAutomizerObserver from plugin BuchiAutomizer for "de.uni_freiburg.informatik.ultimate.plugins.generator.cacsl2boogietranslator AST 08.09 02:43:27" (2/3) ... [2023-09-08 14:43:28,093 INFO L204 PluginConnector]: Invalid model from BuchiAutomizer for observer de.uni_freiburg.informatik.ultimate.plugins.generator.buchiautomizer.BuchiAutomizerObserver@4c503e03 and model type de.uni_freiburg.informatik.ultimate.plugins.generator.buchiautomizer AST 08.09 02:43:28, skipping insertion in model container [2023-09-08 14:43:28,093 INFO L99 BuchiAutomizer]: Safety of program was proven or not checked, starting termination analysis [2023-09-08 14:43:28,093 INFO L184 PluginConnector]: Executing the observer BuchiAutomizerObserver from plugin BuchiAutomizer for "de.uni_freiburg.informatik.ultimate.plugins.generator.rcfgbuilder CFG 08.09 02:43:28" (3/3) ... [2023-09-08 14:43:28,094 INFO L332 chiAutomizerObserver]: Analyzing ICFG parallel-parallel-sum-2.wvr.c [2023-09-08 14:43:28,217 INFO L144 ThreadInstanceAdder]: Constructed 18 joinOtherThreadTransitions. [2023-09-08 14:43:28,245 INFO L73 FinitePrefix]: Start finitePrefix. Operand has 291 places, 301 transitions, 674 flow [2023-09-08 14:43:28,316 INFO L124 PetriNetUnfolderBase]: 21/251 cut-off events. [2023-09-08 14:43:28,316 INFO L125 PetriNetUnfolderBase]: For 6/6 co-relation queries the response was YES. [2023-09-08 14:43:28,331 INFO L83 FinitePrefix]: Finished finitePrefix Result has 280 conditions, 251 events. 21/251 cut-off events. For 6/6 co-relation queries the response was YES. Maximal size of possible extension queue 8. Compared 301 event pairs, 0 based on Foata normal form. 0/230 useless extension candidates. Maximal degree in co-relation 215. Up to 3 conditions per place. [2023-09-08 14:43:28,331 INFO L82 GeneralOperation]: Start removeDead. Operand has 291 places, 301 transitions, 674 flow [2023-09-08 14:43:28,340 INFO L88 GeneralOperation]: Finished RemoveDead, result has has 249 places, 251 transitions, 550 flow [2023-09-08 14:43:28,357 INFO L303 stractBuchiCegarLoop]: Interprodecural is true [2023-09-08 14:43:28,357 INFO L304 stractBuchiCegarLoop]: Hoare is false [2023-09-08 14:43:28,357 INFO L305 stractBuchiCegarLoop]: Compute interpolants for ForwardPredicates [2023-09-08 14:43:28,357 INFO L306 stractBuchiCegarLoop]: Backedges is STRAIGHT_LINE [2023-09-08 14:43:28,357 INFO L307 stractBuchiCegarLoop]: Determinization is PREDICATE_ABSTRACTION [2023-09-08 14:43:28,358 INFO L308 stractBuchiCegarLoop]: Difference is false [2023-09-08 14:43:28,358 INFO L309 stractBuchiCegarLoop]: Minimize is MINIMIZE_SEVPA [2023-09-08 14:43:28,358 INFO L313 stractBuchiCegarLoop]: ======== Iteration 0 == of CEGAR loop == BuchiAutomatonCegarLoop ======== [2023-09-08 14:43:28,359 INFO L72 BuchiIsEmpty]: Start buchiIsEmpty. Operand null