rohanpadhye/JQF

ZestGuidance.displayStats throws Divide by zero error

claudeyj opened this issue · 2 comments

claudeyj commented

Hi, thank you for maintaining the powerful Zest tool. I found a minor issue when running zest with the generator written by myself. Maybe it's because I currently don't have a test evaluator that can run for long enough, sometimes it's reporting java.lang.ArithmeticException: / by zero error. The stack trace is as follows:

java.lang.ArithmeticException: / by zero
	at edu.berkeley.cs.jqf.fuzz.ei.ZestGuidance.displayStats(ZestGuidance.java:476)
	at edu.berkeley.cs.jqf.fuzz.ei.ZestGuidance.hasInput(ZestGuidance.java:723)
	at edu.berkeley.cs.jqf.fuzz.junit.quickcheck.FuzzStatement.evaluate(FuzzStatement.java:108)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at edu.berkeley.cs.jqf.fuzz.junit.GuidedFuzzing.run(GuidedFuzzing.java:213)
	at edu.berkeley.cs.jqf.fuzz.junit.GuidedFuzzing.run(GuidedFuzzing.java:159)
	at edu.berkeley.cs.jqf.plugin.FuzzGoal.execute(FuzzGoal.java:381)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:137)
	at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2(MojoExecutor.java:370)
	at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute(MojoExecutor.java:351)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:215)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:171)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:163)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:117)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:81)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:56)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:294)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:192)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:105)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:960)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:293)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:196)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:282)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:225)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:406)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:347)

ZestGuidance.java:476 is inside the displayStats method and I assume there should be some guarantee that interlvalTrials should be non-zero. Otherwise when the iterval is too short it will be zero and lead to the unchecked exception. Should that be fixed?

rohanpadhye commented

Very interesting, thanks for reporting. I will look into it and push a fix, most likely a zero-check to line 472:

JQF/fuzz/src/main/java/edu/berkeley/cs/jqf/fuzz/ei/ZestGuidance.java

Line 472 in 146ae4d

if (intervalMilliseconds < STATS_REFRESH_TIME_PERIOD && !force) {
. Feel free to open a PR if you have already fixed this locally.

claudeyj commented

Thanks for taking a look! I've created a PR and hope it can fix this issue!

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