[mpich-discuss] Dataloop error message

[Palmer, Bruce J]

For this test, I believe the underlying put/get/accumulate are using simple contiguous data types. Puts and gets use MPI_CHAR, the accumulates use a data type that is dependent on what type of data is being accumulated. In this case it should be MPI_DOUBLE.

-----Original Message-----
From: Latham, Robert J. [mailto:robl at mcs.anl.gov] 
Sent: Thursday, March 09, 2017 9:23 AM
To: discuss at mpich.org
Subject: Re: [mpich-discuss] Dataloop error message

On Wed, 2017-03-08 at 23:41 +0000, Palmer, Bruce J wrote:
> Rob,
> 
> Attached are the valgrind logs for a failed run. I've checked out the 
> code on our side and I don't see anything obviously bogus (not that 
> that means much). Do these suggest anything to you? I'm still trying 
> to create a short reproducer, but as you can imagine, all my efforts 
> so far work just fine.

Yeah, these valgrind logs look ok.  The warnings about uninitialized bytes are common especially when MPICH not configured with extra debugging to explicitly zero out all those buffers.

The dataloop code is getting some kind of garbage datatype.  What types are you trying to use?  Simple contiguous types?  A deeply nested complex user-defined type?

==rob

> 
> Bruce
> 
> -----Original Message-----
> From: Latham, Robert J. [mailto:robl at mcs.anl.gov]
> Sent: Wednesday, March 08, 2017 7:26 AM
> To: discuss at mpich.org
> Subject: Re: [mpich-discuss] Dataloop error message
> 
> On Tue, 2017-03-07 at 19:31 +0000, Palmer, Bruce J wrote:
> > Hi,
> >  
> > I’m trying to track down a possible race condition in a test program 
> > that is using MPI RMA from MPICH 3.2. The program repeats a series 
> > of put/get/accumulate operations to different processors. When I’m 
> > running on 1 node 4 processors everything is fine but when I move to
> > 2  nodes 4 processors I start getting failures. The error messages 
> > I’m seeing are
> >  
> > Assertion failed in file
> > src/mpid/common/datatype/dataloop/dataloop.c
> > at line 265: 0
> 
> that's a strange one!  that came from the "Dataloop_update" routine. 
> It updates pointers after a copy operation.  That particular assertion 
> came from the "handle different types" switch
> 
>     switch(dataloop->kind & DLOOP_KIND_MASK)
> 
> which  means somehow this code got a datatype that was not one of 
> CONTIG, VECTOR, BLOCKINDEXED, INDEXED, or STRUCT  (in dataloop terms.
> MPI type "HINDEXED" for example maps to INDEXED directly, so not all 
> MPI types are explicitly handled).
> 
>  
> > Assertion failed in file
> > src/mpid/common/datatype/dataloop/dataloop.c
> > at line 157: dataloop->loop_params.cm_t.dataloop
> 
> Also inside "Dataloop_update".  This assertion
> 
>     DLOOP_Assert(dataloop->loop_params.cm_t.dataloop)
> 
> basically suggests garbage was passed to the Dataloop_update routine.
>  
> > Does anyone have a handle on what these routines do and what kind of 
> > behavior is generating these errors? The test program is allocating 
> > memory and using it to create a window, followed immediately by a 
> > call to MPI_Win_lock_all to create a passive synchronization epoch.
> > I’ve been using request based RMA calls (Rput, Rget, Raccumulate) 
> > followed by an immediate call to MPI_Wait  for the individual RMA 
> > operations. Any suggestions about what these errors are telling me?
> > If I start putting in print statements to narrow down the location 
> > of the error, the code runs to completion.
> 
> The two assertions plus your observation that "printf debugging makes 
> it go away" sure sounds a lot like some kind of memory corruption.  
> Any chance you can collect some valgrind logs?
> 
> ==rob
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