[Llvm-bgq-discuss] Details behind MPI wrapper for bgclang++

[Jeff Hammond]

Should be deterministic. I've tested that before (a year ago maybe)
because of symmetric heap implementations. However, that's with static
linkage.

Sent from my iPhone

On Mar 1, 2013, at 4:47 PM, Hal Finkel <hfinkel at anl.gov> wrote:

> ----- Original Message -----
>> From: "Jeff Hammond" <jeff.science at gmail.com>
>> To: "Hal Finkel" <hfinkel at anl.gov>
>> Cc: "Jack Poulson" <jack.poulson at gmail.com>, "Jeff Hammond" <jhammond at alcf.anl.gov>,
>> llvm-bgq-discuss at lists.alcf.anl.gov
>> Sent: Friday, March 1, 2013 3:43:04 PM
>> Subject: Re: [Llvm-bgq-discuss] Details behind MPI wrapper for bgclang++
>>
>> I can't think of a PAMI issue here but I have no experience with
>> dynamic linking on BGQ.
>
> I was just wondering how reproducible addresses returned from malloc() are when running the same problem.
>
> -Hal
>
>>
>> Sent from my iPhone
>>
>> On Mar 1, 2013, at 4:39 PM, Hal Finkel <hfinkel at anl.gov> wrote:
>>
>>> ----- Original Message -----
>>>> From: "Jack Poulson" <jack.poulson at gmail.com>
>>>> To: "Hal Finkel" <hfinkel at anl.gov>
>>>> Cc: "Jeff Hammond" <jhammond at alcf.anl.gov>,
>>>> llvm-bgq-discuss at lists.alcf.anl.gov
>>>> Sent: Friday, March 1, 2013 3:07:17 PM
>>>> Subject: Re: [Llvm-bgq-discuss] Details behind MPI wrapper for
>>>> bgclang++
>>>>
>>>> On Fri, Mar 1, 2013 at 1:03 PM, Jack Poulson <
>>>> jack.poulson at gmail.com
>>>>> wrote:
>>>>
>>>>
>>>>
>>>>
>>>> On Fri, Mar 1, 2013 at 12:43 PM, Hal Finkel < hfinkel at anl.gov >
>>>> wrote:
>>>>
>>>>
>>>>
>>>>
>>>> The lightweight core files are really text files, I looked at the
>>>> line:
>>>> While executing instruction at..........0x000000000100c7c4
>>>>
>>>> Then I ran powerpc64-bgq-linux-objdump -C -d Backproj-2d and
>>>> looked
>>>> at the assembly around address 100c7c4 (if you search for it in
>>>> the
>>>> file, note that objdump may omit the leading 0s in the address).
>>>>
>>>>
>>>>
>>>>
>>>> Thanks!
>>>>
>>>>
>>>>
>>>>
>>>> Can you try compiling/linking with
>>>> /home/projects/llvm/r175919-20130222/bin/bgclang++ instead of the
>>>> default one; this is a newer build and I'd like to see if it still
>>>> has whatever bug is yielding this miscompile.
>>>>
>>>>
>>>> Strangely enough, my executable ran correctly with the new version
>>>> of
>>>> LLVM (and passed my accuracy tests). I'm rerunning it again right
>>>> now to help rule out whether or not that was a fluke.
>>>>
>>>> Any ideas as to what might have been the major change in the new
>>>> release?
>>>>
>>>>
>>>>
>>>> Sigh. It was a fluke.
>>>
>>> Hrmm... this being something that sometimes works is interesting.
>>> Are there any sources of non-determinism here? [I suppose that
>>> running on different partitions could cause PAMI to malloc memory
>>> differently; Jeff?]
>>>
>>>>
>>>> Perhaps we should take this offline to avoid spamming everyone
>>>> else
>>>> on the list? I will try linking statically next.
>>>
>>> Let's see if static linking "fixes" it; the list would certainly
>>> like to know that ;)
>>>
>>> -Hal
>>>
>>>>
>>>> Jack
>>>>
>>>>
>>