Fixed several compilation warnings

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorExecutor.h b/unsupported/Eigen/CXX11/src/Tensor/TensorExecutor.h
index c3edae4..5c3d4d6 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorExecutor.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorExecutor.h

@@ -135,7 +135,7 @@
     {
       const Index PacketSize = Vectorizable ? unpacket_traits<typename Evaluator::PacketReturnType>::size : 1;
       const Index size = array_prod(evaluator.dimensions());
-      int num_threads = device.numThreads();
+      size_t num_threads = device.numThreads();
 #ifdef EIGEN_USE_COST_MODEL
       if (num_threads > 1) {
         num_threads = TensorCostModel<ThreadPoolDevice>::numThreads(

diff --git a/unsupported/Eigen/CXX11/src/ThreadPool/RunQueue.h b/unsupported/Eigen/CXX11/src/ThreadPool/RunQueue.h
index aaa1d92..0544a6e 100644
--- a/unsupported/Eigen/CXX11/src/ThreadPool/RunQueue.h
+++ b/unsupported/Eigen/CXX11/src/ThreadPool/RunQueue.h

@@ -168,7 +168,7 @@
       // larger than it is during concurrent modifications. E.g. pop can
       // decrement size before the corresponding push has incremented it.
       // So the computed size can be up to kSize + 1, fix it.
-      if (size > kSize) size = kSize;
+      if (size > static_cast<int>(kSize)) size = kSize;
       return size;
     }
   }

diff --git a/unsupported/test/cxx11_runqueue.cpp b/unsupported/test/cxx11_runqueue.cpp
index 6c99eb9..d1770ee 100644
--- a/unsupported/test/cxx11_runqueue.cpp
+++ b/unsupported/test/cxx11_runqueue.cpp

@@ -30,11 +30,11 @@
   RunQueue<int, 4> q;
   // Check empty state.
   VERIFY(q.Empty());
-  VERIFY_IS_EQUAL(0, q.Size());
+  VERIFY_IS_EQUAL(0u, q.Size());
   VERIFY_IS_EQUAL(0, q.PopFront());
   std::vector<int> stolen;
   VERIFY_IS_EQUAL(0, q.PopBackHalf(&stolen));
-  VERIFY_IS_EQUAL(0, stolen.size());
+  VERIFY_IS_EQUAL(0u, stolen.size());
   // Push one front, pop one front.
   VERIFY_IS_EQUAL(0, q.PushFront(1));
   VERIFY_IS_EQUAL(1, q.Size());