Segmentation fault? about libcspm

[PhilArmstrong]

Looks like calculating Set({1..N}) could be a bit stricter, but even so the powerset of a 25 element set will have 2²⁵ subsets. I doubt this will fit in the memory of your machine.

[PhilArmstrong]

(A quick back of the envelope calculation suggests that you might fit the resultant set in 3Gb or so of memory, given the likely Haskell representation. I could be out by a factor of two or more quite easily though.)

[tomgr]

@annonymouse how exactly were you using it when it produced the error? For example, were you using Set in a datatype/channel declaration etc?

As Phil says, a set of size 2^25 is going to use a lot of memory so it's probably inadvisable to do that.

Thanks for letting us know though - we can certainly try and improve the situation.

[annonymouse]

@PhilArmstrong cheers for the sanity :) I can only blame the time of the night. In some sense it's better that it failed early or I would have been scratching my head a bit as to why things were taking so long. My approach here was bit flawed but I've changed it slightly anyway.

@tomgr For that error specifically I was using it in the interpreter, github slightly borked my copy/paste job there. I managed to reduce it to a Set({1..19}).

Welcome to FDR 3.0.0 (521b22cd118f0a02ade8a95ac96b294148a7c122)
Type :help for help
>  Set({1..19})
panic: the program has detected an inconsistent internal state.
This means that there is a bug in libcspm, not a bug in your input script.
Please report this bug using the contact link at https://www.cs.ox.ac.uk/projects/fdr/.
In particular, please include the input script that caused this error and a brief
description of how to reproduce the problem. Please also include the following message:
    stack overflow

Given the error tells me to report the bug, I felt guilty not doing so :) This is on a 4 core i7 with 16GB of memory - although I suspect the segmentation fault won't depend on that as it occurs very quickly and the FDR process doesn't seem to be consuming many resources when it does this (although I haven't actually traced it to confirm). As you say, this is a strange thing to be doing so I wouldn't worry too much.

Specifically I was using it in a comprehension to generate sets of events up front rather than generating them on the fly - which may have been flawed given that the size of the problem increases a lot very quickly 😄

I'm happy to close this issue - but let me know if you wanted to know any more.

[tomgr]

Ahh ok thanks. Certainly trying to print that set might cause problems (I think there are a few space leaks in the pretty printer), but you should be able to use the set in iterations such as { x | x <- Set({...}) } etc. You will need an unfortunate quantity of RAM mind you!

Thanks for letting us know anyhow.