#2201: added enums to specify transfer strategy

src/vt/vrt/collection/balance/temperedlb/tempered_enums.h

@@ -165,6 +165,36 @@ enum struct KnowledgeEnum : uint8_t {
   Log         = 2
 };
 
+/// Enum for the strategy to be used in transfer stage
+enum struct TransferStrategyEnum : uint8_t {
+  /**
+   * \brief Original strategy
+   *
+   * Transfer one object per transfer as in original Grapevine approach.
+   */
+  Original   = 0,
+  /**
+   * \brief Original strategy improved by recursion
+   *
+   * When single object transfer is rejected, attempt to recurse in order to
+   * pull more objects into the transfer and hereby minimize work added by
+   * said transfer.
+   * This is especially useful when communication is taken into account, as
+   * object transfers typically disrupt local vs. global communication edges.
+   */
+  Recursive  = 1,
+  /**
+   * \brief Form object clusters and attempt to perform swaps.
+   *
+   * Object can be clustered according to arbitrary definition, and swaps
+   * of entire clusters, according the nullset, between ranks are attempted.
+   * This is especially useful when shared memory constraints are present,
+   * as breaking shared memory clusters results in higher overall memory
+   * footprint, in constrast with whole cluster swaps.
+   */
+  ClusterSwap = 2,
+};
+
 }}}} /* end namespace vt::vrt::collection::lb */
 
 #endif /*INCLUDED_VT_VRT_COLLECTION_BALANCE_TEMPEREDLB_TEMPERED_ENUMS_H*/