[mpich-discuss] MPI-IO bug

[Rob Latham]

On 05/01/2014 10:53 AM, Rob Latham wrote:
>
>
> 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

incorrect.  this change is to ADIOI_Calc_my_offset_len, common to both 
read and write paths.

I'm still concerned about tiling and proper recording of UB and LB, 
though... still digging.

==rob

> ?
>> @@ -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