[mpich-discuss] MPI_File_set_view Error: ADIOI_Count_contiguous_blocks

[Rob Ross]

Hi Ingo,

You've hit a problem in the combination of ROMIO and MPI  
implementation. Can you tell us what MPI version you are using?

In the mean time you may want to instead use a struct with an MPI_LB/ 
MPI_UB pair to extend your type, rather than using resize.

Otherwise I think that you're on the right track.

Rob

On May 29, 2008, at 8:59 AM, Ingo Bojak wrote:

> I've been having trouble setting a file view which has blocks of  
> different lengths of doubles, with gaps in between, and potentially  
> gaps in the beginning and end. Since this is the first time using  
> MPI*2*-IO, I thought the errors were from mistakes in resizing to  
> get holes at the beginning/end. But it seems that the resizing per  
> se is the problem. Somewhat edited code snippet follows:
>
> ---
> // lb: lower bound, ext: extend
> MPI_Aint lb,ext;
>
> // noblo: number of blocks, disp: list of displacements, blen: list  
> of block lengths
> int noblo,*disp,*blen;
>
> // sdump: file handle, stat: file status
> MPI_File sdump;
> MPI_Status stat;
>
> // datatype used for filetype
> MPI_Datatype loc_double;
>
> if (MPI_Type_indexed(noblo,blen,disp,MPI_DOUBLE,&loc_double)! 
> =MPI_SUCCESS)
> sstop("setview: typing loc_double",ERR60);
>
> if (MPI_Type_get_extent(loc_double,&lb,&ext)!=MPI_SUCCESS)
>  sstop("setview: get extent double",ERR61);
>
> // *** the following lines to be commented out ***
>
> if (MPI_Type_create_resized(loc_double,lb,ext,&loc_double)! 
> =MPI_SUCCESS)
>  sstop("setview: resize loc_double",ERR62);
>
> // *** the previous lines to be commented out ***
>
> if (MPI_Type_commit(&loc_double)!=MPI_SUCCESS)
>  sstop("setview: commit loc_double",ERR63);
>
> if (MPI_File_open(MPI_COMM_WORLD,sdname,MPI_MODE_CREATE |  
> MPI_MODE_WRONLY, MPI_INFO_NULL,&sdump)!=MPI_SUCCESS)
>  sstop("stdump: can't open file",ERR56);
>
> // error occurs in the line below, *if* lines above are *not*  
> commented out
> if (MPI_File_set_view(sdump, 
> 0,MPI_DOUBLE,loc_double,"native",MPI_INFO_NULL)!=MPI_SUCCESS)
>  sstop("stdump: can't set view",ERR57);
> ---
>
> "sstop" is just my wrapper for MPI_Abort with some error output. If  
> the indicated lines are commented out, the program runs fine  
> (although the output is wrong). If the indicated lines are in, I get  
> the following error:
>
> Error: Unsupported datatype passed to ADIOI_Count_contiguous_blocks,  
> combiner = 18
>
> The program is the aborted since I trigger on lack of MPI_SUCCESS.  
> Note that the resize leaves everything as it was before in the above  
> (not so in the original code, of course - but I was getting the same  
> error when I was actually resizing with intent). A simplified, but  
> otherwise typical, version of what may be found in noblo, blen, and  
> disp:
>
> Intended writing pattern for ranks 0,1,2:
> 0011010022122202
>
> rank 0
> ------
> noblo=4;
> disp[4]={0, 4, 6,14};
> blen[4]={2,1,2,1};
>
> rank 1
> ------
> noblo=3;
> dis[3]={2,5,10};
> blen[3]={2,1,1};
>
> rank 2
> ------
> noblo=2;
> dis[2]={8,11};
> blen[3]={2,3};
>
> I would have then tried to resize the index-datatype to  
> lb=0,ext=16*8 or perhaps lb=current_lb,ext=16*8-current_lb. I'm not  
> sure which one of the two is correct so that multiple writes advance  
> all ranks such that they alway write in the same intended block  
> pattern. But anyhow, I couldn't make progress on that because of the  
> above error which seems to be independent of the actual resize made.
>
> The whole thing runs usually currently under Cygwin on a WinXP box:
> mpicc -Wall prog.c
> mpiexec -n 16  ./a.exe
> I use the single machine for rapid debugging. But I have also  
> started this on one of the target clusters (Linux, gcc) and I get  
> exactly  the same problem!
>
> Am I being stupid (likely...) or is there some problem with the MPI  
> library function? Any ideas?
>
> Thanks,
> Ingo
>