[mpich-discuss] MPI-IO bug

[Rob Latham]

On 04/09/2014 02:52 PM, Wei-keng Liao wrote:

>
> The patch below can fix this problem. Hope it does not break other tests.

I'm uncertain about this patch...

> Index: adio/common/ad_read_coll.c

it should have been in the write path, correct
?
> @@ -368,13 +368,16 @@
>   #endif
>           if (file_ptr_type == ADIO_INDIVIDUAL) {
>              /* Wei-keng reworked type processing to be a bit more
> efficient */
> +            for (i=0; i<flat_file->count; i++) /* skip blocklens[] == 0 */
> +                if (flat_file->blocklens[i] > 0) break;
> +

the flat_file->blocklens[] array might contain a UB and LB marker.  The 
marker will be stored in the flattened representation with a zero-length 
element at a particular offset.  So if you resize a type, your flattened 
representation would be like this:
(offset: 50, length: 0),
(offset: 100, length: 1024),
(offset: 200, length: 0)

furthermore, ADIOI_Optimize_flatten will coalesce multiple zero-length 
elements into one, but will leave the first and last elements alone.

>               offset       = fd->fp_ind - disp;
> -            n_filetypes  = (offset - flat_file->indices[0]) /
> filetype_extent;
> +            n_filetypes  = (offset - flat_file->indices[i]) /
> filetype_extent;

doesn't this mess up tiling of the file view?

==rob

>               offset      -= (ADIO_Offset)n_filetypes * filetype_extent;
>               /* now offset is local to this extent */
>
>               /* find the block where offset is located, skip
> blocklens[i]==0 */
> -            for (i=0; i<flat_file->count; i++) {
> +            for (; i<flat_file->count; i++) {
>                   ADIO_Offset dist;
>                   if (flat_file->blocklens[i] == 0) continue;
>                   dist = flat_file->indices[i] + flat_file->blocklens[i]
> - offset;
>
> Wei-keng
>
>
>
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-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA