Renaming /doc to /docs for use with GitHub Pages

[jpf-core.git] / doc / jpf-core / IdleFilter.md

diff --git a/doc/jpf-core/IdleFilter.md b/doc/jpf-core/IdleFilter.md
deleted file mode 100644 (file)
index 03c6e98..0000000
--- a/doc/jpf-core/IdleFilter.md
+++ /dev/null
@@ -1,99 +0,0 @@
-# IdleFilter #
-
-The `gov.nasa.jpf.listener.IdleFilter` is a listener that can be used to close state spaces with loops. Consider a simple "busy waiting" loop
-
-~~~~~~~~ {.java}
-for (long l=0; l<10000000; l++);
-~~~~~~~~
-
-While not a good thing to do in general, it is benign if executed in a normal VM. For JPF, it causes trouble because it adds a lot of useless steps to the stored path, and slows down execution considerably.
-
-In addition, people who expect JPF to match states can get surprised by programs like
-
-~~~~~~~~ {.java}
-while (true){
-  // no transition break in here
-}
-~~~~~~~~
-not being state matched, and hence not terminating (it wouldn't terminate in a normal VM either). 
-
-`IdleFilter` is a little tool to deal with such (bad) loops. It counts the number of back-jumps it encounters within the same thread and stackframe, and if this number exceeds a configured threshold it takes one of the following actions:
-
- * warn - just prints out a warning that we have a suspicious loop
- * break - breaks the transition at the back-jump `goto` instruction, to allow state matching
- * prune - sets the transition ignored, i.e. prunes the search tree
- * jump - skips the back-jump. This is the most dangerous action since you better make sure the loop does not contain side-effects your program depends on.
-
-
-### Properties ###
-Consequently, there are two options:
-
- * `idle.max_backjumps = \<number\>` : max number of back-jumps that triggers the configured action (default 500)
- * `idle.action = warn|break|prune|jump` : action to take when number of back-jumps exceeds threshold
-
-### Examples ###
-
-**(1)** The test program
-
-~~~~~~~~ {.java}
-...
-public void testBreak () {
-  int y = 4;
-  int x = 0;
-
-  while (x != y) { // JPF should state match on the backjump
-    x = x + 1;
-    if (x > 3) {
-      x = 0;
-    }
-  }
-}
-~~~~~~~~
-
-would never terminate under JPF or a host VM. Running it with
-
-~~~~~~~~ {.bash}
-> bin/jpf +listener=.listener.IdleFilter +idle.action=break ...
-~~~~~~~~
-
-does terminate due to state matching and produces the following report
-
-~~~~~~~~ {.bash}
-...
-====================================================== search started: 4/8/10 4:14 PM
-[WARNING] IdleFilter breaks transition on suspicious loop in thread: main
-        at gov.nasa.jpf.test.mc.basic.IdleLoopTest.testBreak(gov/nasa/jpf/test/mc/basic/IdleLoopTest.java:42)
-...
-====================================================== results
-no errors detected
-~~~~~~~~
-
------
-**(2)** The following program would execute a long time under JPF
-
-~~~~~~~~ {.java}
-...
-public void testJump () {
-  for (int i=0; i<1000000; i++){
-    //...
-  }
-
-  System.out.println("Ok, jumped past loop");
-}
-~~~~~~~~
-
-If we run it with
-
-~~~~~~~~ {.bash}
-> bin/jpf +listener=.listener.IdleFilter +idle.action=jump ...
-~~~~~~~~
-
-JPF comes back quickly with the result
-
-~~~~~~~~ {.bash}
-====================================================== search started: 4/8/10 4:20 PM
-[WARNING] IdleFilter jumped past loop in: main
-        at gov.nasa.jpf.test.mc.basic.IdleLoopTest.testJump(gov/nasa/jpf/test/mc/basic/IdleLoopTest.java:74)
-Ok, jumped past loop
-...
-~~~~~~~~