[Beowulf] mpich program segfaults

Glen Kaukola glen at mail.cert.ucr.edu
Wed Mar 3 15:46:36 EST 2004

Suvendra Nath Dutta wrote:

> Glen,
>     Does your program seg fault when compiled with debugging off or on?

Either way.

> Sometimes compilers will initialize arrays when compiling for 
> debugging, but not waste time doing that when compiled without debugging.

The arguments being passed to the subroutine are two arrays of real 
numbers and a few integers.  Nothing being passed to the subroutine has 
been dynamically allocated.  The compiler, IBM's XLF compiler, 
initializes the array to 0.  At least I'm pretty sure it does, since I 
can print things before the subroutine call.

> Also if you compile with optimization which line follows which one 
> isn't always clear.

I don't have any optimizations turned on.

> You want to make sure you aren't over-running memory.

The machine has 2 gigs of memory, which should be plenty.  The same 
program runs on an x86 machine with 1 gig of memory just fine (I'm 
trying to get the program working on an Apple G5 by the way).

> Also you want to be sure its nothing to do with MPICH. Try calling the 
> subroutine from a serial program if possible.

I've tried telling mpirun to only use one cpu and I get the same 
results.  I've also tried running the program all by itself and it still 
crashes.  Like I said though, it runs just fine under the a debugger.

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