This is normal. Since v9 there's a second kernel run for the private use of the front end.

Hello I've been able to duplicate this.

(M10, Macbook 10.9.4, 16GB. M10 is using the the higher performance of the two graphics cards NVIDIA GeForce GT 750M 2048 MB).

The kernel is quiting and leaving no messages as to why, and did not write anything to the system log. The kernel crashes upon evaluation (not during writing the .stl), but did so only after several evaluations. From a fresh kernel and after evaluating your code:

Do[Print[i]; Print[Timing[tmp = CurveA[i];]], {i, 1, 50}]

The kernel died at the 12th iteration, and then again at the 3rd iteration. So, it appears to be random.

This code is not using very much memory.

tmp = CurveA[18]
N@ByteCount@tmp

indicates that the result is only about 6MB (I am not seeing much of a spike in memory during the computation). The resulting .stl is also only about 6MB.

You can reduce memory usage during a Mathematica session by setting

$HistoryLength = 0 (*or some small positive integer*)

However, I don't think it will help in this particular case.

I'm guessing that this behavior indicates a bug.

Thank you both, that sounds right. Is it safe to say that v10 uses more memory than v9 in some situations? Is there anything I should disable to make it use less memory?

Hi Bryan,

I'm afraid I can't reproduce your problem, both Export statements evaluate just fine for me (Mathematica 10 on a Windows 7 machine). However, if I were to guess, I'd say that what you're seeing is not a mysterious clearing of variables, but a quitting and restarting of the Kernel. That can happen e.g. when a computation exhausts resources (like memory), so maybe your problem is hiding somewhere in that general direction... But since I don't even see the error, that's obviously just a blind guess.