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Fun with overflow!

Posted By: Timothy Chow
Date: Monday, 7 January 2019, at 4:38 p.m.

In Response To: rules for this tourney? (Stick)

The following observations were made on my laptop; it's possible that other architectures may yield different results (e.g., 32-bit versus 64-bit).

Thanks to Stick's tip, I learned that it's the number after the first colon in the XGID that indicates the current cube value (as opposed to the "maximum" cube value). Evidently, even though the drop-down menu limits the maximum cube value to 1024, the current cube value can go higher than that. I copied the XGID to a text file and manually edited the current cube value to various values. Note: the XGID uses a logarithmic scale, so that for example a "10" really means 210 = 1024.

First I tried the following experiment: (1) manually edit the cube value in the XGID to something large; (2) copy and paste the XGID into an XG window; (3) copy the XG position as Text and paste it back into my text editor (Notepad, for example). Doing this, I found that I could get the cube up as high as 260 (or maybe it was 262; I don't quite remember). If I tried higher numbers, then in step (3) I would just get the XGID back again, without the diagram of the board.

The second experiment I tried went as follows. Steps (1) and (2) were the same as above. Then I tried to "Play from position" and then resign a single game, to see how many points I would lose. In this experiment, I found that if the cube were 232 or higher, resignation would cost me 0 points. If the cube were 230 or lower, resignation would cost me the expected number of points. The most amusing case was 231. Resigning would then cost me a large negative number of points!

It's not clear to me how these astronomical cube values interact with the "maximum cube value" feature of XG. It could be that the maximum cube value prevents XG from getting past 210 in actual play, even though you can manufacture higher cube values when editing.

By the way, if the cube goes past 64, XG introduces a second cube next to the first cube. Exercise for the reader: Find a way to get this "second cube" to be a green check mark or a red cross.

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