Fix share memory collision in multi-communicator case.

Current SHM object name would only use pidHash and ranks as
identification, which would collide each other when program runs with
multiple communicators. Here we added commId info into pidHash, it makes
'pidHash'es of different communicators keeping in same process will be
distincted with each other.

src/include/utils.h

@@ -11,6 +11,7 @@
 #include <stdint.h>
 
 ncclResult_t getHostName(char* hostname, int maxlen);
+uint64_t getnHash(const char* string, int n);
 uint64_t getHostHash();
 uint64_t getPidHash();
 

src/init.cu

@@ -302,12 +302,12 @@ static void showVersion() {
   }
 }
 
-static ncclResult_t fillInfo(struct ncclPeerInfo* info, int rank) {
+static ncclResult_t fillInfo(struct ncclPeerInfo* info, int rank, uint64_t commHash) {
   info->rank = rank;
   CUDACHECK(cudaGetDevice(&info->cudaDev));
   NCCLCHECK(getNvmlDevice(info->cudaDev, &info->nvmlDev))
-  info->hostHash=getHostHash();
-  info->pidHash=getPidHash();
+  info->hostHash=getHostHash()+commHash;
+  info->pidHash=getPidHash()+commHash;
 
   // Get PCI Bus Id. We need to get the bus ID through CUDA first, since the
   // cudaDev is a CUDA runtime dev number which could be different from the
@@ -679,7 +679,8 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
 
   int rank = comm->rank;
   int nranks = comm->nRanks;
-  TRACE(NCCL_INIT, "rank %d nranks %d - BEGIN", rank, nranks);
+  uint64_t commHash = getnHash(commId->internal, NCCL_UNIQUE_ID_BYTES);
+  TRACE(NCCL_INIT, "comm %p, commHash %lu, rank %d nranks %d - BEGIN", comm, commHash, rank, nranks);
   NCCLCHECK(bootstrapInit(commId, rank, nranks, &comm->bootstrap));
 
   // AllGather1 - begin
@@ -690,7 +691,7 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
 
   NCCLCHECK(ncclCalloc(&allGather1Data, nranks));
   allGather1Data[rank].comm = comm;
-  NCCLCHECK(fillInfo(&allGather1Data[rank].peerInfo, rank));
+  NCCLCHECK(fillInfo(&allGather1Data[rank].peerInfo, rank, commHash));
   NCCLCHECK(bootstrapAllGather(comm->bootstrap, allGather1Data, sizeof(*allGather1Data)));
 
   NCCLCHECK(ncclCalloc(&comm->peerInfo, nranks));
@@ -960,7 +961,7 @@ static ncclResult_t initTransportsAll(struct ncclComm** comms, const int* devs,
   NCCLCHECK(ncclCalloc(&allInfo, nranks));
   for (int rank=0; rank<nranks; rank++) {
     CUDACHECK(cudaSetDevice(devs[rank]));
-    NCCLCHECK(fillInfo(allInfo+rank, rank));
+    NCCLCHECK(fillInfo(allInfo+rank, rank, 0));
   }
 
   int* connectTransport;

src/misc/utils.cu

@@ -96,6 +96,15 @@ uint64_t getHash(const char* string) {
   return result;
 }
 
+uint64_t getnHash(const char* string, int n) {
+  // Based on DJB2, result = result * 33 + char
+  uint64_t result = 9527;
+  for (int c = 0; c < n; c++) {
+    result = ((result << 5) + result) + string[c];
+  }
+  return result;
+}
+
 /* Generate a hash of the unique identifying string for this host
  * that will be unique for both bare-metal and container instances
  * Equivalent of a hash of;