Wei-keng, I've already let this slip longer than I intended. I've opened a ticket [1], which I intend to close pretty quickly http://trac.mpich.org/projects/mpich/ticket/2073 ==rob On 04/09/2014 02:52 PM, Wei-keng Liao wrote:

(This bug is probably caused by my patch long ago.) Attached is a program extracted from an application that can reproduce the problem observed from a large run. The problem is when defining a filetype using MPI_Type_indexed and the first few elements of argument blocklens[] are zeros, a collective write will miss writing some data.

The test program first fills a file with 9 integers with values all -999. It then defines a filetype and writes to the file in parallel with user buffers with value all 1s. Lastly, the file is read back and checked for contents.

Command used to compile and run the test program: mpicc -g -o bug_indexed_io bug_indexed_io.c mpiexec -n 2 bug_indexed_io

Stdout: 0: Error: unexpected varlue at buf[7] == -999

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

Index: adio/common/ad_read_coll.c @@ -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; + offset = fd->fp_ind - disp; - n_filetypes = (offset - flat_file->indices[0]) / filetype_extent; + n_filetypes = (offset - flat_file->indices[i]) / filetype_extent; 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