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lab4 [2017/01/27 19:48] – francklab4 [2018/11/06 15:55] (current) – franck
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 +~~NOTOC~~
 +
 +====== LAB 3 ======
 +
 +====== Listeners ======
 +
 +
 Choose one of the following listeners (please don't all choose the first one).  Write one or more sample programs to illustrate the use of the listener.  Some listeners have associated properties.  Illustrate their use as well.  Describe the listener and its properties.  The source code of the listeners can be found in jpf-core/src/main/gov/nasa/jpf/listener/ Choose one of the following listeners (please don't all choose the first one).  Write one or more sample programs to illustrate the use of the listener.  Some listeners have associated properties.  Illustrate their use as well.  Describe the listener and its properties.  The source code of the listeners can be found in jpf-core/src/main/gov/nasa/jpf/listener/
  
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       * vt.max_vars       * vt.max_vars
       * vt.methods       * vt.methods
 +
 +To receive feedback, submit your work as a text file using the submit command before Tuesday January 29:\\
 +submit 4315 lab3 <name of the listener> 
 +
 +====== Sample ======
 +
 +The listener BudgetChecker, which is part of the package gov.nasa.jpf.listener, allows us to
 +set constraints for JPF.  For example, one can set the maximum number of milliseconds used
 +by JPF.  If JPF takes more time than this maximum when using this listener, JPF will 
 +terminate and will report that it took more than the set maximum.  Apart from the amount time used, we
 +can also constrain the amount of heap space used, the number of instructions executed,
 +the depth of the search, the number of new states, and the number of non-replayed new states.
 +To specify these constraints, the listener has several properties that can be set in the 
 +application properties file, as we will show below.
 +
 +To illustrate the BudgetChecker listener, we consider the following app.
 +
 +<code java>
 +import java.util.ArrayList;
 +import java.util.List;
 +import java.util.Random;
 +
 +public class Constraints {
 +    public static void main(String[] args) {
 +        Random random = new Random();
 +        List<Integer> list = new ArrayList<Integer>();
 +        for (int i = 0; random.nextBoolean(); i++) {
 +            list.add(new Integer(i));
 +        }
 +    }
 +}
 +</code>
 +
 +We can run the listener BudgetChecker without setting any of its properties
 +and, hence, not setting any constraints, as shown in the application properties file below.
 +
 +<code>
 +target=Constraints 
 +classpath=.
 +cg.enumerate_random=true
 +listener=gov.nasa.jpf.listener.BudgetChecker
 +</code>
 +
 +In this case, no constraints are set.  As a result, JPF will run out of memory producing
 +the following output
 +
 +<code>
 +JavaPathfinder core system v8.0 (rev 29) - (C) 2005-2014 United States Government. All rights reserved.
 +
 +
 +====================================================== system under test
 +Constraints.main()
 +
 +====================================================== search started: 1/27/17 1:01 PM
 +[SEVERE] JPF out of memory
 +...
 +</code>
 +
 +We can constrain the maximum amount time used by JPF to 1000 milliseconds as follows.
 +We can assign any long value to the property budget.max_time.
 +
 +<code>
 +target=Constraints
 +classpath=.
 +cg.enumerate_random=true
 +listener=gov.nasa.jpf.listener.BudgetChecker
 +budget.max_time=1000
 +</code>
 +
 +Since JPF cannot complete within one second, it stops after one second and produces the following output. 
 +
 +<code>
 +JavaPathfinder core system v8.0 (rev 29) - (C) 2005-2014 United States Government. All rights reserved.
 +
 +
 +====================================================== system under test
 +Constraint.main()
 +
 +====================================================== search started: 1/27/17 1:22 PM
 +
 +====================================================== search constraint
 +max time exceeded: 00:00:01 >= 00:00:01
 +...
 +</code>
 +
 +The amount heap space used by JPF can be constrained to a maximum number of bits as follows.
 +We can assign any long value to the property budget.max_heap.
 +
 +<code>
 +target=Constraints
 +classpath=.
 +cg.enumerate_random=true
 +listener=gov.nasa.jpf.listener.BudgetChecker
 +budget.max_heap=10000000
 +</code>
 +
 +Note that 10000000 bits = 10000000 / (1024 * 1024) megabytes = 9.5 megabytes.  Since
 +JPF needs more heap space, it stops and produces the following output.
 +
 +<code>
 +JavaPathfinder core system v8.0 (rev 29) - (C) 2005-2014 United States Government. All rights reserved.
 +
 +
 +====================================================== system under test
 +Constraints.main()
 +
 +====================================================== search started: 1/27/17 1:36 PM
 +
 +====================================================== search constraint
 +max heap exceeded: 10MB >= 9MB
 +...
 +</code>
 +
 +One can constrain JPF from checking more than 100 bytecode instructions as follows.
 +We can assign any long value to the property budget.max_insn.
 +
 +<code>
 +target=Constraints
 +classpath=.
 +cg.enumerate_random=true
 +listener=gov.nasa.jpf.listener.BudgetChecker
 +budget.max_insn=100
 +</code>
 +
 +Since this constraint is violated, JPF produces the following output.
 +
 +<code>
 +JavaPathfinder core system v8.0 (rev 29) - (C) 2005-2014 United States Government. All rights reserved.
 +
 +
 +====================================================== system under test
 +Constraints.main()
 +
 +====================================================== search started: 1/27/17 1:47 PM
 +
 +====================================================== search constraint
 +max instruction count exceeded: 100
 +...
 +</code>
 +
 +We can also limit the number of states that JPF explores by setting the property budget.max_state.  We can assign any int value to this property. 
 +
 +<code>
 +target=Constraints
 +classpath=.
 +cg.enumerate_random=true
 +listener=gov.nasa.jpf.listener.BudgetChecker
 +budget.max_state=100
 +</code>
 +
 +Since the statespace of this app consists of more than 100 states, JPF stops and produces the following output.
 +
 +<code>
 +JavaPathfinder core system v8.0 (rev 29) - (C) 2005-2014 United States Government. All rights reserved.
 +
 +
 +====================================================== system under test
 +Constraints.main()
 +
 +====================================================== search started: 1/27/17 1:48 PM
 +
 +====================================================== search constraint
 +max states exceeded: 100
 +...
 +</code>
 +
 +We can also constrain the depth of the search.  The corresponding property, budget.max_depth, can take any int value.
 +
 +<code>
 +target=Constraints
 +classpath=.
 +cg.enumerate_random=true
 +listener=gov.nasa.jpf.listener.BudgetChecker
 +budget.max_depth=100
 +</code>
 +
 +Since the depth of the search is greater than 100 for this app, JPF stops and produces the following output.
 +
 +<code>
 +JavaPathfinder core system v8.0 (rev 29) - (C) 2005-2014 United States Government. All rights reserved.
 +
 +
 +====================================================== system under test
 +Constraints.main()
 +
 +====================================================== search started: 1/27/17 1:53 PM
 +
 +====================================================== search constraint
 +max search depth exceeded: 100
 +...
 +</code>
 +
  
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