optimizing some code

src/clib/pio_darray_int.c

@@ -2153,3 +2153,51 @@ int pio_sorted_copy(const void *array, void *sortedarray, io_desc_t *iodesc, int
     }
     return PIO_NOERR;
 }
+
+/**
+ * Compute the maximum aggregate number of bytes. This is called by
+ * subset_rearrange_create() and box_rearrange_create().
+ *
+ * @param ios pointer to the IO system structure.
+ * @param iodesc a pointer to decomposition description.
+ * @returns 0 for success, error code otherwise.
+ * @author Jim Edwards
+ */
+int compute_maxaggregate_bytes(iosystem_desc_t *ios, io_desc_t *iodesc)
+{
+    int maxbytesoniotask = INT_MAX;
+    int maxbytesoncomputetask = INT_MAX;
+    int maxbytes;
+    int mpierr;  /* Return code from MPI functions. */
+
+    /* Check inputs. */
+    pioassert(iodesc, "invalid input", __FILE__, __LINE__);
+
+    LOG((2, "compute_maxaggregate_bytes iodesc->maxiobuflen = %d iodesc->ndof = %d",
+         iodesc->maxiobuflen, iodesc->ndof));
+
+    /* Determine the max bytes that can be held on IO task. */
+    if (ios->ioproc && iodesc->maxiobuflen > 0)
+        maxbytesoniotask = pio_buffer_size_limit / iodesc->maxiobuflen;
+
+    /* Determine the max bytes that can be held on computation task. */
+    if (ios->comp_rank >= 0 && iodesc->ndof > 0)
+        maxbytesoncomputetask = pio_cnbuffer_limit / iodesc->ndof;
+
+    /* Take the min of the max IO and max comp bytes. */
+    maxbytes = min(maxbytesoniotask, maxbytesoncomputetask);
+    LOG((2, "compute_maxaggregate_bytes maxbytesoniotask = %d maxbytesoncomputetask = %d",
+         maxbytesoniotask, maxbytesoncomputetask));
+
+    /* Get the min value of this on all tasks. */
+    LOG((3, "before allreaduce maxbytes = %d", maxbytes));
+    if ((mpierr = MPI_Allreduce(MPI_IN_PLACE, &maxbytes, 1, MPI_INT, MPI_MIN,
+                                ios->union_comm)))
+        return check_mpi(NULL, mpierr, __FILE__, __LINE__);
+    LOG((3, "after allreaduce maxbytes = %d", maxbytes));
+
+    /* Remember the result. */
+    iodesc->maxbytes = maxbytes;
+
+    return PIO_NOERR;
+}

src/clib/pio_internal.h

@@ -249,6 +249,8 @@ extern "C" {
     /* Flush contents of multi-buffer to disk. */
     int flush_output_buffer(file_desc_t *file, bool force, PIO_Offset addsize);
 
+    int compute_maxaggregate_bytes(iosystem_desc_t *ios, io_desc_t *iodesc);
+
     /* Compute the size that the IO tasks will need to hold the data. */
     int compute_maxIObuffersize(MPI_Comm io_comm, io_desc_t *iodesc);