change the tag to be a positive value. handle 0-byte situations correctly.

ompi/mca/fcoll/dynamic_gen2/fcoll_dynamic_gen2_file_write_all.c

@@ -33,7 +33,7 @@
 
 
 #define DEBUG_ON 0
-#define FCOLL_DYNAMIC_GEN2_SHUFFLE_TAG   -123
+#define FCOLL_DYNAMIC_GEN2_SHUFFLE_TAG   123
 
 /*Used for loading file-offsets per aggregator*/
 typedef struct mca_io_ompio_local_io_array{
@@ -502,6 +502,7 @@ int mca_fcoll_dynamic_gen2_file_write_all (mca_io_ompio_file_t *fh,
     prev_reqs = reqs2;
     
     /* Initialize communication for iteration 0 */
+    if ( cycles > 0 ) {
         for ( i=0; i<dynamic_gen2_num_io_procs; i++ ) {
             ret = shuffle_init ( 0, cycles, aggregators[i], fh->f_rank, aggr_data[i], 
                                  &curr_reqs[i*(fh->f_procs_per_group + 1)] );
@@ -509,6 +510,7 @@ int mca_fcoll_dynamic_gen2_file_write_all (mca_io_ompio_file_t *fh,
                 goto exit;
             }
         }
+    }
 
 
     for (index = 1; index < cycles; index++) {
@@ -548,6 +550,7 @@ int mca_fcoll_dynamic_gen2_file_write_all (mca_io_ompio_file_t *fh,
 
 
     /* Finish communication for iteration i = cycles-1 */
+    if ( cycles > 0 ) {
         SWAP_REQUESTS(curr_reqs,prev_reqs);
         SWAP_AGGR_POINTERS(aggr_data,dynamic_gen2_num_io_procs); 
         
@@ -568,6 +571,7 @@ int mca_fcoll_dynamic_gen2_file_write_all (mca_io_ompio_file_t *fh,
                 free (aggr_data[i]->prev_send_buf);
             }
         }
+    }
 
         
 #if OMPIO_FCOLL_WANT_TIME_BREAKDOWN
@@ -706,6 +710,7 @@ static int shuffle_init ( int index, int cycles, int aggregator, int rank, mca_i
     MPI_Aint global_count = 0;
 
     data->num_io_entries = 0;
+    data->bytes_sent = 0;
     data->io_array=NULL;
     data->send_buf=NULL;
     /**********************************************************************