StackOverflowError for recursion of type a <- b, b <- a #8
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Hi Thomas,
I think that the problem here is that the program is not a valid Datalog
program for Bigdatalog because there is no base relation.
…On Sat, Oct 14, 2017, 2:42 PM Thomas Rebele ***@***.***> wrote:
Hello,
I tried to minimize #7 <#7>
further. I arrived at
a(X,Y) <- b(X,Y).
b(X,Y) <- a(X,Y).
which leads to a StackOverflowError:
Exception in thread "main" java.lang.StackOverflowError
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateRecursiveOperator(ProgramGenerator.java:1439)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateOperator(ProgramGenerator.java:186)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateOperators(ProgramGenerator.java:249)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateCliqueOperator(ProgramGenerator.java:1616)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateRecursiveOperator(ProgramGenerator.java:1472)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateOperator(ProgramGenerator.java:186)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateOperators(ProgramGenerator.java:249)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateCliqueOperator(ProgramGenerator.java:1616)
...
and then the stack trace repeats again and again
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Hi, with query I still get an StackOverflowError, but with a different stack trace: |
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Still the same problem, a is an intensional relation. To make it work you
have to add another (extensional) relation c and populate a from c:
a(X,Y) <- c(X,Y).
a(X,Y) <- b(X,Y).
b(X,Y) <- a(X,Y).
database({ c(X:string, Y:string) }).
…On Sun, Oct 15, 2017 at 3:44 AM, Thomas Rebele ***@***.***> wrote:
Hi,
thanks for the idea. I tried it with an input relation:
a(X,Y) <- b(X,Y).
b(X,Y) <- a(X,Y).
database({ a(X:string, Y:string) }).
with query b(A,B).
I still get an StackOverflowError, but with a different stack trace:
Exception in thread "main" java.lang.StackOverflowError
at java.lang.StringBuilder.append(StringBuilder.java:136)
at edu.ucla.cs.wis.bigdatalog.compiler.predicate.DerivedPredicate.toString(DerivedPredicate.java:43)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.BasicClique.toString(BasicClique.java:49)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.isXYClique(XYCliqueAnalyzer.java:338)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.isXYClique(XYCliqueAnalyzer.java:329)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.findXYLiteralType(XYCliqueAnalyzer.java:574)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.findXYRuleType(XYCliqueAnalyzer.java:439)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.isXYClique2(XYCliqueAnalyzer.java:292)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.isXYClique(XYCliqueAnalyzer.java:273)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.isXYClique(XYCliqueAnalyzer.java:347)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.isXYClique(XYCliqueAnalyzer.java:329)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.findXYLiteralType(XYCliqueAnalyzer.java:574)
at edu.ucla.cs.wis.bigdatalog.compiler.analysis.XYCliqueAnalyzer.findXYRuleType(XYCliqueAnalyzer.java:439)
...
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That gives me still another StackOverflowError: |
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Ok then it is a bug :)
…On Sun, Oct 15, 2017 at 12:30 PM, Thomas Rebele ***@***.***> wrote:
That gives me still another StackOverflowError:
Exception in thread "main" java.lang.StackOverflowError
at java.util.ArrayList.iterator(ArrayList.java:834)
at edu.ucla.cs.wis.bigdatalog.compiler.predicate.graph.PCGAndNode.isNonLinearRecursive(PCGAndNode.java:80)
at edu.ucla.cs.wis.bigdatalog.compiler.recursion.Clique.determineRecursiveType(Clique.java:110)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateCliqueOperator(ProgramGenerator.java:1558)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateRecursiveOperator(ProgramGenerator.java:1472)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateOperator(ProgramGenerator.java:186)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateOperators(ProgramGenerator.java:249)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateCliqueOperator(ProgramGenerator.java:1616)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateRecursiveOperator(ProgramGenerator.java:1472)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateOperator(ProgramGenerator.java:186)
at edu.ucla.cs.wis.bigdatalog.interpreter.relational.ProgramGenerator.generateOperators(ProgramGenerator.java:249)
...
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I can reproduce the bug. It is surprise that the relation is that simple. |
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Hello,
I tried to minimize #7 further. I arrived at
which leads to a StackOverflowError:
and then the stack trace repeats again and again
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