From 609b3337a701e322d0e33089b826d1ac7c2a11fe Mon Sep 17 00:00:00 2001
From: Benoit Steiner <benoit.steiner.goog@gmail.com>
Date: Sat, 27 Feb 2016 20:42:57 +0000
Subject: [PATCH] Print some information to stderr when a CUDA kernel fails

---
 unsupported/Eigen/CXX11/src/Tensor/TensorDeviceCuda.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorDeviceCuda.h b/unsupported/Eigen/CXX11/src/Tensor/TensorDeviceCuda.h
index c01704e56..821835cf3 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorDeviceCuda.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorDeviceCuda.h
@@ -211,8 +211,12 @@ struct GpuDevice {
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void synchronize() const {
 #if defined(__CUDACC__) && !defined(__CUDA_ARCH__)
     cudaError_t err = cudaStreamSynchronize(stream_->stream());
-    EIGEN_UNUSED_VARIABLE(err)
-    assert(err == cudaSuccess);
+    if (err != cudaSuccess) {
+      std::cerr << "Error detected in CUDA stream: "
+                << cudaGetErrorString(err)
+                << std::endl;
+      assert(err == cudaSuccess);
+    }
 #else
     assert(false && "The default device should be used instead to generate kernel code");
 #endif