f size <i>num_export</i> listing the processor IDs to which
exported objects should be assigned (i.e., the destination processors).
<br>All processors may pass <i>export_procs</i>=NULL if 
import lists are provided and 
<i>export_procs</i> is not
needed by callback functions
<a href="ug_query_mig.html#ZOLTAN_PRE_MIGRATE_PP_FN"><b>ZOLTAN_PRE_MIGRATE_PP_FN</b></
a>,
<a href="ug_query_mig.html#ZOLTAN_MID_MIGRATE_PP_FN"><b>ZOLTAN_MID_MIGRATE_PP_FN</b></
a>, and 
<a href="ug_query_mig.html#ZOLTAN_POST_MIGRATE_PP