[petsc-users] Bus Error

[Jed Brown]

I'm thinking of something such as writing floating point data into the return address, which would be unaligned/garbage.

Reproducing under Valgrind would help a lot.  Perhaps it's possible to checkpoint such that the breakage can be reproduced more quickly?

Barry Smith <bsmith at petsc.dev> writes:

> https://en.wikipedia.org/wiki/Bus_error <https://en.wikipedia.org/wiki/Bus_error>
>
> But perhaps not true for Intel? 
>
>
>
>> On Aug 24, 2020, at 1:06 PM, Matthew Knepley <knepley at gmail.com> wrote:
>> 
>> On Mon, Aug 24, 2020 at 1:46 PM Barry Smith <bsmith at petsc.dev <mailto:bsmith at petsc.dev>> wrote:
>> 
>> 
>> > On Aug 24, 2020, at 12:39 PM, Jed Brown <jed at jedbrown.org <mailto:jed at jedbrown.org>> wrote:
>> > 
>> > Barry Smith <bsmith at petsc.dev <mailto:bsmith at petsc.dev>> writes:
>> > 
>> >>> On Aug 24, 2020, at 12:31 PM, Jed Brown <jed at jedbrown.org <mailto:jed at jedbrown.org>> wrote:
>> >>> 
>> >>> Barry Smith <bsmith at petsc.dev <mailto:bsmith at petsc.dev>> writes:
>> >>> 
>> >>>> So if a BLAS errors with SIGBUS then it is always an input error of just not proper double/complex alignment? Or some other very strange thing?
>> >>> 
>> >>> I would suspect memory corruption.
>> >> 
>> >> 
>> >>  Corruption meaning what specifically?
>> >> 
>> >>  The routines crashing are dgemv which only take double precision arrays, regardless of what garbage is in those arrays i don't think there can be BUS errors resulting. They don't take integer arrays whose corruption could result in bad indexing and then BUS errors. 
>> >> 
>> >>  So then it can only be corruption of the pointers passed in, correct?
>> > 
>> > Such as those pointers pointing into data on the stack with incorrect sizes.
>> 
>> But won't incorrect sizes "usually" lead to SEGV not SEGBUS?
>> 
>> My understanding was that roughly memory errors in the heap are SEGV and memory errors on the stack are SIGBUS. Is that not true?
>> 
>>    Matt
>> 
>> -- 
>> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
>> -- Norbert Wiener
>> 
>> https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>