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Ben Hekster's avatar

Another interpretation of the “infinity times infinitesimal error” statement is just to realize that the staircase only _appears_ to converge to the diagonal; if you zoom in closely enough you see that the staircase never in fact actually converges. So there is no real mystery; it’s just a matter of scale

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skybrian's avatar

To calculate the path error, we need to already know the correct answer. This seems a bit unsatisfying.

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lcamtuf's avatar

What do you mean? I don't think you need any prior assumptions, other than the definition of the construction method (which is spelled out in the "proof").

I did spoil the conclusion by giving the answer before we calculate it, but that's because I didn't want to make it too long-winded. The point is that you need to precisely define what you're modeling and not assume that the two effects are the same.

Edit: rephrased the text a bit to move one half of the conclusion down the line.

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skybrian's avatar

Uh, actually I'm wrong, the only assumption needed is that n != 2. Since ePath is 2 - n, if n were 2 then the error would always be zero. Since it's not 2 then we can show it doesn't converge.

Assuming n < 2 is pretty reasonable - we are saying that a stair-step is an approximation.

Edit: then again, it would be rather strange to not to allow ourselves to use the Pythagorean theorem. Perhaps all we need to say is that when we replace a right triangle with smaller right triangles, c doesn't converge on a + b, and that's all there is to it. To converge, the angle between a and b would need to increase from 90 towards 180 degrees as we shrink them.

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Iustin Pop's avatar

For some reason, to me, this makes sense intuitively, while on your previous article I mentioned that 0.(9) still bothers me somehow.

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