[mpich-discuss] Problem with ADIOI_Info_get (MPI_Info_get) from the ADIO layer

[Matthieu Dorier]

Hi, 

I found the solution by investigating the code so I'll post it here in case it can be useful to someone else: 

When opening a file, ADIOI_xxx_SetInfo is called to copy the info structure. Unless overwritten by the ADIO backend, it's ADIO_GEN_SetInfo (in src/mpi/romio/adio/common/ad_hints.c) that ends up being called and this function only copies the hints that it knows (e.g. cb_buffer_size). So the solution consists in changing ADIO_GEN_SetInfo or (more appropriately) provide an implementation of ADIOI_xxx_SetInfo that copies custom parameters and the called ADIO_GEN_SetInfo. 

Matthieu 

----- Mail original -----

> De: "Matthieu Dorier" <matthieu.dorier at irisa.fr>
> À: discuss at mpich.org
> Envoyé: Lundi 24 Juin 2013 15:46:21
> Objet: [mpich-discuss] Problem with ADIOI_Info_get (MPI_Info_get)
> from the ADIO layer

> Hi,

> I'm implementing an ADIO backend and I'm having problems retrieving
> values from the MPI_Info attached to the file.
> On the application side, I have something like this:

> MPI_Info_create(&info);
> MPI_Info_set(info,"cb_buffer_size","64");
> MPI_Info_set(info,"xyz","3");
> MPI_File_open(comm, "file",
> MPI_MODE_WRONLY | MPI_MODE_CREATE, info, &fh);

> then a call to a MPI_File_write, which ends up calling my
> implementation of ADIOI_xxx_WriteContig. In this function, I try to
> read back these info:

> int info_flag;
> char* value = (char *)
> ADIOI_Malloc((MPI_MAX_INFO_VAL+1)*sizeof(char));
> ADIOI_Info_get(fd->info, "xyz", MPI_MAX_INFO_VAL, value,&info_flag);
> if(info_flag) fprintf(stderr,"xyz = %d\n",atoi(value));
> ADIOI_Info_get(fd->info, "cb_buffer_size", MPI_MAX_INFO_VAL,
> value,&info_flag);
> if(info_flag) fprintf(stderr,"cb_buffer_size = %d\n",atoi(value));

> I can get the 64 associated to the cb_buffer_size key (which is a
> reserved hint), but I don't get the second value.
> Where does the problem come from?
> I tried everything: re-ordering the calls, changing the name of the
> key, calling MPI_Info_get in the application to check that the
> values are properly set (they are)...

> Thanks

> Matthieu Dorier
> PhD student at ENS Cachan Brittany and IRISA
> http://people.irisa.fr/Matthieu.Dorier

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