Escaping Infinite Loops

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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Illiac had infinite loop detection

[uigrad_2000]

Here at the U of I, we built the 4th computer ever made: the Illiac

24 hours a day, an operator would sit at the computer to operate it. "Software" or jobs would be submitted by faculty. When one finished, the operator would load the next one.

Since only one job could be running at a time, it was quite important to detect infinite loops. The last bit of the ALU was connected to a speaker, and would produce sound similar to static when the computer was running correctly. If an infinite loop was encountered, then the static would suddenly hum a pitch, and the operator would kick out the job, and move to the next.

As the story goes, the very first machine music was written by a math professor, and submitted as an Illiac job, as a prank on the operator. Sometime around 3am, the operator picked up the next job and fed it to the machine. Immediately, the Illiac began playing "Hail to the Orange"!