Bug #1651
SEGV subsets ??
Description
This was a surprise:
/**/ L := 1..5000; /**/ S := subsets(L,2); Process cocoa5 segmentation fault (core dumped)
The crash came relatively quickly (30s, maybe)
Stack overflow? top did not report excessive memory usage (about 1Gbyte)
History
#1
Updated by John Abbott over 2 years ago
Updated by On Julian's computer (Linux, CoCoA-5.3.3b), it gave a controlled CoCoA-5 error: "too many recursive calls" (or similar).
Why did mine SEGV?
#2
Updated by John Abbott over 2 years ago
- Status changed from New to In Progress
- % Done changed from 0 to 10
I have just used ulimit to increase my stacksize limit, and now I get "too many recursions":
--> ERROR: Too many nested scopes --> WHERE: at line 46 (column 24) of combinatoria.cpkg5 --> If N = 1 Then Return [[X] | X In S]; EndIf; --> ^^^^^^^^^^^^^^
I suppose we should re-write subsets so that it does not recurse too deeply.
#3
Updated by Anna Maria Bigatti over 2 years ago
Updated by On my Mac I get
--> ERROR: Too many nested scopes
#4
Updated by John Abbott about 2 years ago
- Status changed from In Progress to Resolved
- Assignee set to John Abbott
- % Done changed from 10 to 70
I have modified the impl of SubsetsN in combinatoria.cpkg5 so that it handles 2-subsets specially (avoiding recursion).
My computer SEGV'd because of stack overflow. Not sure why. Julian's Linux box had the same stack limit but didn't overflow.
Anyway, the non-recursive impl should now avoid that problem completely.
Marked as resolved.
#5
Updated by John Abbott about 2 years ago
- Status changed from Resolved to Closed
- % Done changed from 70 to 100
- Estimated time set to 0.99 h
Too much stress to keep this open any longer. I'm pretty sure it is fixed now (and faster too).
Let the users do the testing -- that's what everyone else seems to do!