diff --git a/src/Makefile b/src/Makefile
index 2814646..7c0d1f8 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -49,8 +49,8 @@ ifeq ($(MPI), 1)
 HIPCUFLAGS += -DMPI_SUPPORT -I${MPI_HOME}/include -I${MPI_HOME}/include/mpi
 HIPLDFLAGS += -L${MPI_HOME}/lib -lmpi
 else ifeq ($(MPICH), 1)
-HIPCUFLAGS += -DMPI_SUPPORT -I/usr/include/mpich -I/usr/include/x86_64-linux-gnu/mpich
-HIPLDFLAGS += -L/usr/lib -lmpich
+HIPCUFLAGS += -DMPI_SUPPORT -I/usr/include/mpich -I/usr/include/x86_64-linux-gnu/mpich -I/usr/include/mpich-x86_64/
+HIPLDFLAGS += -L/usr/lib -L/usr/lib64/mpich/lib/ -lmpich
 endif
 
 LIBRARIES += rccl
diff --git a/src/alltoallv.cu b/src/alltoallv.cu
index 5bab307..b9f4d32 100644
--- a/src/alltoallv.cu
+++ b/src/alltoallv.cu
@@ -8,7 +8,7 @@
 #include "cuda_runtime.h"
 #include "common.h"
 
-#define USE_RCCL_GATHER_SCATTER
+//#define USE_RCCL_GATHER_SCATTER
 
 void AlltoAllvGetCollByteCount(size_t *sendcount, size_t *recvcount, size_t *paramcount, size_t *sendInplaceOffset, size_t *recvInplaceOffset, size_t count, int nranks) {
   if (count < nranks*nranks/2) {
@@ -54,12 +54,12 @@ testResult_t AlltoAllvInitData(struct threadArgs* args, ncclDataType_t type, ncc
     size_t chunksize = data_count/nranks;
     for (int j=0; j<nranks; j++) {
       size_t scount = 0, rcount = ((j+rank)%nranks)*chunksize;
-      if ((j+rank)%nranks == 0)
+      if (j+rank == nranks-1)
         rcount += (sendcount-chunksize*(nranks-1)*nranks/2);
       size_t sdisp = 0;
       for (int k=0; k<nranks; k++) {
         scount = ((k+j)%nranks)*chunksize;
-        if ((k+j)%nranks == 0)
+        if (k+j == nranks-1)
           scount += (sendcount-chunksize*(nranks-1)*nranks/2);
         if (k == rank)
           break;
@@ -105,7 +105,7 @@ testResult_t AlltoAllvRunColl(void* sendbuff, void* recvbuff, size_t count, nccl
   size_t chunksize = count*2/nranks;
   for (int i = 0; i < nranks; i++) {
       size_t scount = ((i+rank)%nranks)*chunksize;
-      if ((i+rank)%nranks == 0)
+      if (i+rank == nranks-1)
           scount += (count*nranks-chunksize*(nranks-1)*nranks/2);
       sendcounts[i+rank*nranks] = recvcounts[i+rank*nranks] = scount;
       sdispls[i+rank*nranks] = rdispls[i+rank*nranks] = disp;
@@ -122,7 +122,6 @@ testResult_t AlltoAllvRunColl(void* sendbuff, void* recvbuff, size_t count, nccl
 #else
   NCCLCHECK(ncclGroupStart());
   for (int r=0; r<nranks; r++) {
-    if (sendcounts[r+rank*nranks] != 0) {
       NCCLCHECK(ncclSend(
           ((char*)sendbuff) + sdispls[r+rank*nranks] * wordSize(type),
           sendcounts[r+rank*nranks],
@@ -130,8 +129,6 @@ testResult_t AlltoAllvRunColl(void* sendbuff, void* recvbuff, size_t count, nccl
           r,
           comm,
           stream));
-    }
-    if (recvcounts[r+rank*nranks] != 0) {
       NCCLCHECK(ncclRecv(
           ((char*)recvbuff) + rdispls[r+rank*nranks] * wordSize(type),
           recvcounts[r+rank*nranks],
@@ -139,7 +136,6 @@ testResult_t AlltoAllvRunColl(void* sendbuff, void* recvbuff, size_t count, nccl
           r,
           comm,
           stream));
-    }
   }
   NCCLCHECK(ncclGroupEnd());
 #endif