[mpich-discuss] Displaying source after attaching to an MPI job

[Rob Latham]

On 09/22/2015 03:38 PM, Peter Thompson wrote:
> This question came to me in my support role for TotalVIew.   When you
> are debugging an MPI job, and attach after the job goes parallel, why
> don't you see the source for the main program? Instead you are usually
> located in the assembler code someplace, in some library above
> MPI_Init,  and you have to go down the stack frame to see the source for
> your program.

We're trying our hardest to get a release out the door, so since this 
doesn't quite rise to the level of freeze-breaking worthy, I've stashed 
this in a ticket to help us not forget about it:

http://trac.mpich.org/projects/mpich/ticket/2305

==rob

>
> There is a solution though.   Way back when, when the MPIR_proctable
> interface was designed to help the debugger acquire processes
> automatically, there was a global variable defined MPIR_force_to_main.
> If this is defined in debugger.c as a global variable, then indeed, when
> you start up TotalView.   Here's a diff of the change:
>
> *** debugger.c~ 2015-07-22 17:59:51.000000000 -0400
> --- debugger.c  2015-09-22 16:18:21.000000000 -0400
> ***************
> *** 11,17 ****
>    int MPIR_proctable_size = 0;
>    int MPIR_i_am_starter = 0;
>    int MPIR_partial_attach_ok = 0;
> !
>    volatile int MPIR_debug_state = 0;
>    char *MPIR_debug_abort_string = 0;
>
> --- 11,17 ----
>    int MPIR_proctable_size = 0;
>    int MPIR_i_am_starter = 0;
>    int MPIR_partial_attach_ok = 0;
> ! int MPIR_force_to_main = 0;
>    volatile int MPIR_debug_state = 0;
>    char *MPIR_debug_abort_string = 0;
>
>
> The MPI being discussed was Intel MPI, but I've always understood that
> to be based on MPICH, and I thought this would be a good place to
> start.   I had the same discussion in the Open MPI group a few years
> ago, and they had dropped the variable at one point since it did not
> appear to be used in any way.   The code certainly doesn't make use of
> it, but when the debugger starts looking for it, that's when the magic
> happens.  ;-)  I tried just defining the variable in debugger.h, but I
> think it got optimized away since I just set up
>
> extern int MPIR_force_to_main;
>
> and didn't assign a value at that point.
>
> Cheers,
> PeterT
>

-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA
_______________________________________________
discuss mailing list     discuss at mpich.org
To manage subscription options or unsubscribe:
https://lists.mpich.org/mailman/listinfo/discuss