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Programming

Escaping Infinite Loops 204

Posted by Unknown Lamer
from the pc-losering dept.
twocentplain writes in with an MIT news release about Jolt, a research project designed to unfreeze software stuck in an infinite loop (for a subset of infinite loops). It uses a combination of static instrumentation (using LLVM) and a run time watchdog that checks the program state during loop iteration; when a duplicate state is detected it permits the user to take one a few actions to escape the loop. The authors claim it works well enough that the program can often continue operating properly. The original paper contains detailed case studies.
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Escaping Infinite Loops

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  • yipes (Score:2, Insightful)

    by Anonymous Coward on Tuesday August 02, 2011 @05:09PM (#36964978)

    bad programmers can now sink to new lows...

  • Loop invariants (Score:4, Insightful)

    by Anonymous Coward on Tuesday August 02, 2011 @05:09PM (#36964980)
    So you just jump to an address outside of the loop and hope that your loop invariant hasn't been violated?
  • by kwiqsilver (585008) on Tuesday August 02, 2011 @06:16PM (#36965758)
    So...if the computer eventually gives in to entropy, it's not an infinite loop?
  • Re:Halting Problem (Score:4, Insightful)

    by dido (9125) <dido@@@imperium...ph> on Tuesday August 02, 2011 @09:51PM (#36967588)

    True, as Marvin Minsky had once said: "...any finite-state machine, if left completely to itself, will fall eventually into a perfectly periodic repetitive pattern. The duration of this repeating pattern cannot exceed the number of internal states of the machine..." Emphasis in original. BUT, don't let that statement deceive you, as the number of states available to even a computer with very modest memory is so large that even the word 'astronomical' doesn't do it justice. For instance, my first real computer, a humble Commodore 64, with only 64K of memory, can have a total of 2^524288 (65536 * 8) states, something of the order of 1e157826 (yes, 157,826 zeroes after your one!) states. To give some idea of just how big that number of states is, were you to try to cycle through all such states at the astounding rate of 1e17 states per second (a theoretical 100 petahertz machine capable of cracking 56-bit DES keys in less than one second), it would still take 1e157801 years to go through them all. The heat death of the universe will have taken place after less than a thousandth part of that time has elapsed. As such Minsky goes on to say: "...the magnitudes involved should lead one to suspect that theorems and arguments based chiefly on the mere finiteness [of] the state diagram may not carry a great deal of significance." (Marvin Minsky quotes come from Computation, Finite and Infinite Machines, 1967).

You can do this in a number of ways. IBM chose to do all of them. Why do you find that funny? -- D. Taylor, Computer Science 350

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