API: document that distances may only group if latencies

Signed-off-by: Brice Goglin <[email protected]>

Author: bgoglin

include/hwloc/distances.h

@@ -404,7 +404,8 @@ HWLOC_DECLSPEC int hwloc_distances_add_values(hwloc_topology_t topology,
 /** \brief Flags for adding a new distances to a topology. */
 enum hwloc_distances_add_flag_e {
   /** \brief Try to group objects based on the newly provided distance information.
-   * This is ignored for distances between objects of different types.
+   * Grouping is only performed when the distances structure contains latencies,
+   * and when all objects are of the same type.
    * \hideinitializer
    */
   HWLOC_DISTANCES_ADD_FLAG_GROUP = (1UL<<0),