Re: [OMPI devel] bug in opal_generic_simple_pack_function()

Mon, 25 Nov 2013 08:12:38 -0500 (EST) 

George,

Thx for the detailed answer!
I did my tests on a v1.6.2 (changeset: 141b22222759).
After you told me it worked for you with earlier releases, I looked at the changesets applied since that time. I guess 28fd94d282a3is the one that fixes my issue? 

Regards,
Nadia

On 25/11/2013 13:36, George Bosilca wrote:

Nadia,


Which version of Open MPI are you using? I tried with the nightly 
r29751, the current 1.6 and the current 1.7 and I __always__ got the 
expected output.



There is a simple way to show what the datatype engine is doing. You 
can set the MCA parameters
mpi_ddt_unpack_debug and mpi_ddt_pack_debug to get more info. If you 
only want to see how the datatype looks after the MPI_Commit step you 
can call directly ompi_datatype_dump(ddt). This will show the 
internals of the datatype, converted in predefined types.



As an example I took the application you provided and build the 
following picture of what is send and what is received (original 
buffer, send datatype, packed buffer, recv datatype, resulting buffer).




Now using the ompi_datatype_dump, I see the recv and the send 
datatypes as:



-cC---P-DB-[---][---]     OPAL_UINT1 count 8 disp 0x0 (0) extent 1 
(size 8)
-cC---P-DB-[---][---]     OPAL_UINT1 count 8 disp 0x10 (16) extent 1 
(size 8)
-cC---P-DB-[---][---]           OPAL_INT4 count 4 disp 0x30 (48) 
extent 4 (size 16)
----------------------G---[---][---]          OPAL_END_LOOP pref 3 
elements first elem displacement 0 size of data 32



-cC---P-DB-[---][---]     OPAL_UINT1 count 24 disp 0x10 (16) extent 1 
(size 24)
-cC---P-DB-[---][---]     OPAL_UINT1 count 8 disp 0x30 (48) extent 1 
(size 8)
---------G---[---][---]         OPAL_END_LOOP prev 2 elements first 
elem displacement 16 size of data 32


This match perfectly to the datatype drawn by hand.

  George.




On Nov 25, 2013, at 11:40 , Nadia Derbey <nadia.der...@bull.net 
<mailto:nadia.der...@bull.net>> wrote:



Hi,


I'm currently working on a bug occuring at the client site with 
openmpi when calling MPI_Sendreceive() on datatypes built by the 
application.
I think I've found where the bug comes from (it is located in 
opal_generic_simple_pack_function() - file 
opal/datatype/opal_datatype_pack.c). But this code is so complicated 
that I'm more than unsure of my fix. What I can say is that it fixes 
things for me, but I need some advices from the datatypes specialists.


---------------


You will find in attachment the reproducer provided by the client, as 
well as the resulting output.

datatypes.c : reproducer

to run the binary: salloc --exclusive -p B510 -N 1 -n 1 mpirun 
./datatypes

trc_ko: traces got without the patch applied
trc_ok: traces got with the patch applied.

---------------


The proposed patch is the following: (Note that the very first change 
in this patch was enough in my case, but I thought all the 
"source_base" settings should follow this model.)


-------------------------

opal_generic_simple_pack_function: add the datatype lb when 
progressing in the input buffer


diff -r cb23c2f07e1f opal/datatype/opal_datatype_pack.c

--- a/opal/datatype/opal_datatype_pack.c        Sun Nov 24 17:06:51 
2013 +0000
+++ b/opal/datatype/opal_datatype_pack.c        Mon Nov 25 10:48:00 
2013 +0100

@@ -301,7 +301,7 @@ opal_generic_simple_pack_function( opal_
                 PACK_PREDEFINED_DATATYPE( pConvertor, pElem, count_desc,

                                           source_base, destination, 
iov_len_local );

                 if( 0 == count_desc ) {  /* completed */
-                    source_base = pConvertor->pBaseBuf + pStack->disp;

+                    source_base = pConvertor->pBaseBuf + 
pStack->disp + pData->lb;

                     pos_desc++;  /* advance to the next data */

                     UPDATE_INTERNAL_COUNTERS( description, pos_desc, 
pElem, count_desc );

                     continue;
@@ -333,7 +333,7 @@ opal_generic_simple_pack_function( opal_

                         pStack->disp += 
description[pStack->index].loop.extent;

                     }
                 }
-                source_base = pConvertor->pBaseBuf + pStack->disp;

+                source_base = pConvertor->pBaseBuf + pStack->disp + 
pData->lb;
                 UPDATE_INTERNAL_COUNTERS( description, pos_desc, 
pElem, count_desc );
                 DO_DEBUG( opal_output( 0, "pack new_loop count %d 
stack_pos %d pos_desc %d disp %ld space %lu\n",
(int)pStack->count, pConvertor->stack_pos, pos_desc, 
(long)pStack->disp, (unsigned long)iov_len_local ); );

@@ -354,7 +354,7 @@ opal_generic_simple_pack_function( opal_
                             pStack->disp + local_disp);
                 pos_desc++;
             update_loop_description:  /* update the current state */
-                source_base = pConvertor->pBaseBuf + pStack->disp;

+                source_base = pConvertor->pBaseBuf + pStack->disp + 
pData->lb;
                 UPDATE_INTERNAL_COUNTERS( description, pos_desc, 
pElem, count_desc );
                 DDT_DUMP_STACK( pConvertor->pStack, 
pConvertor->stack_pos, pElem, "advance loop" );

                 continue;
@@ -374,7 +374,7 @@ opal_generic_simple_pack_function( opal_
     }
     /* I complete an element, next step I should go to the next one */

     PUSH_STACK( pStack, pConvertor->stack_pos, pos_desc, 
OPAL_DATATYPE_INT8, count_desc,

-                source_base - pStack->disp - pConvertor->pBaseBuf );

+                source_base - pStack->disp - pConvertor->pBaseBuf - 
pData->lb );
     DO_DEBUG( opal_output( 0, "pack save stack stack_pos %d pos_desc 
%d count_desc %d disp %ld\n",
                            pConvertor->stack_pos, pStack->index, 
(int)pStack->count, (long)pStack->disp ); );

     return 0;

-------------------------------

Regards,
Nadia
--
Nadia Derbey
Bull, Architect of an Open World
http://www.bull.com
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--
Nadia Derbey
Bull, Architect of an Open World
http://www.bull.com























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