Mathematica running out of memory

Question

I\'m trying to run the following program, which calculates roots of polynomials of degree up to d with coefficients only +1 or -1, and then store it into files.

Answer 1

Ouch, this is a nasty one.

What's going on is that N will do caching of results in order to speed up future calculations if you need them again. Sometimes this is absolutely what you want, but sometimes it just breaks the world. Fortunately, you do have some options. One is to use the ClearSystemCache command, which does just what it said on the tin. After I ran your un-parallelized loop for a little while (before getting bored and aborting the calculation), MemoryInUse reported ~160 MiB in use. Using ClearSystemCache got that down to about 14 MiB.

One thing you should look at doing, instead of calling ClearSystemCache programmatically, is to use SetSystemOptions to change the caching behavior. You should take a look at SystemOptions["CacheOptions"] to see what the possibilities are.

EDIT: It's not terribly surprising that the caching causes a bigger problem for more complex expressions. It's got to be stashing copies of those expressions somewhere, and more complex expressions require more memory.