fix gloo allreduce_bcube issue for platform010 switch

Summary: fixed a unit test failure in D37416148 after switch gloo to platform010.

Reviewed By: meyering

Differential Revision: D37423180

fbshipit-source-id: 1314386206483287a5e54933c96e786d051dc339

Author: mingzhe09088

gloo/allreduce_bcube.h

@@ -68,8 +68,8 @@ class Node {
     for (int i = 0; i < steps; ++i) {
       peersPerStep_.emplace_back();
     }
-    numElemsPerStep_.reserve(steps);
-    ptrOffsetPerStep_.reserve(steps);
+    numElemsPerStep_.resize(steps);
+    ptrOffsetPerStep_.resize(steps);
   }
   /**
    * Get the rank of this node
@@ -295,7 +295,7 @@ class AllreduceBcube : public Algorithm {
                  std::max(myRank_, destRank));
         sendDataBufs_[destRank] =
             pair->createSendBuffer(slot, ptrs_[0], bytes_);
-        recvBufs_[bufIdx].reserve(recvSize);
+        recvBufs_[bufIdx].resize(recvSize);
         recvDataBufs_[destRank] = pair->createRecvBuffer(
             slot, &recvBufs_[bufIdx][0], recvSize * sizeof(T));
         recvBufIdx_[destRank] = bufIdx;