Integrated RCCL with MSCCL++ for small message sizes (#1231)

src/include/comm.h

@@ -393,6 +393,13 @@ struct ncclComm {
   // shared structures for finalization
   int finalizeRankCnt;
 
+#if defined(ENABLE_MSCCLPP)
+  // Whether this comm is compatible with MSCCLPP
+  bool mscclppCompatible;
+  struct mscclpp_ncclComm* mscclpp_comm;
+  size_t mscclpp_threshold;
+#endif
+
   // Whether this comm is compatible with MSCCL
   bool mscclCompatible;
   // group job to support multi-thread FT

src/include/mscclpp/mscclpp_nccl.h

@@ -0,0 +1,48 @@
+/*************************************************************************
+ * Copyright (c) 2024 Advanced Micro Devices, Inc. All rights reserved.
+ *
+ * See LICENSE.txt and NOTICES.txt for license information
+ ************************************************************************/
+
+#ifndef MSCCLPP_NCCL_H_
+#define MSCCLPP_NCCL_H_
+
+#include "nccl.h"
+#include <unordered_map>
+
+typedef struct mscclpp_ncclComm* mscclpp_ncclComm_t;
+
+typedef struct { char internal[NCCL_UNIQUE_ID_BYTES]; } mscclpp_ncclUniqueId;
+
+bool mscclpp_init();
+
+/* A ncclUniqueId and a mscclpp_ncclUniqueId will always be created together and used alternatively. This maps between them. */
+extern std::unordered_map<ncclUniqueId, mscclpp_ncclUniqueId> mscclpp_uniqueIdMap;
+
+/* See ncclGetUniqueId. */
+extern ncclResult_t  (*mscclpp_ncclGetUniqueId)(mscclpp_ncclUniqueId* uniqueId);
+
+/* See ncclCommInitRank. */
+extern ncclResult_t  (*mscclpp_ncclCommInitRank)(mscclpp_ncclComm_t* comm, int nranks, mscclpp_ncclUniqueId commId, int rank);
+
+/* See ncclCommDestroy. */
+extern ncclResult_t  (*mscclpp_ncclCommDestroy)(mscclpp_ncclComm_t comm);
+
+/* See ncclAllReduce. */
+extern ncclResult_t  (*mscclpp_ncclAllReduce)(const void* sendbuff, void* recvbuff, size_t count,
+    ncclDataType_t datatype, ncclRedOp_t op, mscclpp_ncclComm_t comm, hipStream_t stream);
+
+/* See ncclAllGather. */
+extern ncclResult_t  (*mscclpp_ncclAllGather)(const void* sendbuff, void* recvbuff, size_t sendcount,
+    ncclDataType_t datatype, mscclpp_ncclComm_t comm, hipStream_t stream);
+
+namespace std {
+  template <>
+  struct hash<ncclUniqueId> {
+    size_t operator ()(const ncclUniqueId& uniqueId) const noexcept;
+  };
+}
+
+bool operator ==(const ncclUniqueId& a, const ncclUniqueId& b);
+
+#endif