Pieces of String

Just how long is a piece of string?

a) Twice as long as a piece of string half its length?
b) Just long enough to join its ends?
c) 10e-35 metres
d) As long as my current Mathematica calculation?
e) Shorter than when you last measured it

In the case of d), this calculation has now been running for 17h15m (that's 62,100 seconds), consuming on average about 50% of the power of my Core Duo T7200 processor (and only 400MB of memory), which clocks up about 11 billion instructions per second.

So... thus far the laptop has executed about 310 trillion (that's 310,000,000,000,000) instructions.

Now, for idle comparison - assume the engine of your car runs on average at say, 2,500 RPM while doing 70mph and that it lasts say 200,000 miles

By the time the engine wears out in 2857 driving hours it will have done 428 million revs. If the CPU lasted 428 million cycles it would have worn out in only 42 milliseconds, I would be getting through CPU's at the rate of about 24 per second and would already have got through 1.5 million of them.

Or, looking at it the other way, if your car was only as reliable as the CPU has been for the past 17h15m it would go about ten trillion miles, which is about half way to Alpha Centauri (though at 70mph it would take you about 39 million years)

That's LONG string.

BTW - all the above calculations are highly dubious: I've corrected them twice already. Can't rhyme, can't add. What to do?