From 949a2da38cbfebe358a25dc59b47abb67beb4126 Mon Sep 17 00:00:00 2001
From: RJ Ryan <rjryan@google.com>
Date: Fri, 14 Apr 2017 13:23:35 -0700
Subject: Use scalar_sum_op and scalar_quotient_op instead of operator+ and
 operator/ in MeanReducer.

Improves support for std::complex types when compiling for CUDA.

Expands on e2e9cdd16970914cf0a892fea5e7c4402b3ede41
 and 2bda1b0d93fb627d0c500ec48b20302d44c32cb7
.
---
 .../Eigen/CXX11/src/Tensor/TensorFunctors.h        |  8 +++--
 unsupported/test/cxx11_tensor_complex_cuda.cu      | 36 ++++++++++++++++++++++
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorFunctors.h b/unsupported/Eigen/CXX11/src/Tensor/TensorFunctors.h
index 3b4f8eda1..5dcc3794c 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorFunctors.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorFunctors.h
@@ -166,7 +166,8 @@ template <typename T> struct MeanReducer
     return pset1<Packet>(initialize());
   }
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalize(const T accum) const {
-    return accum / scalarCount_;
+    internal::scalar_quotient_op<T> quotient_op;
+    return quotient_op(accum, T(scalarCount_));
   }
   template <typename Packet>
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet finalizePacket(const Packet& vaccum) const {
@@ -175,7 +176,10 @@ template <typename T> struct MeanReducer
   template <typename Packet>
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalizeBoth(const T saccum, const Packet& vaccum) const {
     internal::scalar_sum_op<T> sum_op;
-    return sum_op(saccum, predux(vaccum)) / (scalarCount_ + packetCount_ * unpacket_traits<Packet>::size);
+    internal::scalar_quotient_op<T> quotient_op;
+    return quotient_op(
+        sum_op(saccum, predux(vaccum)),
+        T(scalarCount_ + packetCount_ * unpacket_traits<Packet>::size));
   }
 
   protected:
diff --git a/unsupported/test/cxx11_tensor_complex_cuda.cu b/unsupported/test/cxx11_tensor_complex_cuda.cu
index d4e111f5d..87cf28920 100644
--- a/unsupported/test/cxx11_tensor_complex_cuda.cu
+++ b/unsupported/test/cxx11_tensor_complex_cuda.cu
@@ -107,6 +107,41 @@ static void test_cuda_sum_reductions() {
   gpu_device.deallocate(gpu_out_ptr);
 }
 
+static void test_cuda_mean_reductions() {
+
+  Eigen::CudaStreamDevice stream;
+  Eigen::GpuDevice gpu_device(&stream);
+
+  const int num_rows = internal::random<int>(1024, 5*1024);
+  const int num_cols = internal::random<int>(1024, 5*1024);
+
+  Tensor<std::complex<float>, 2> in(num_rows, num_cols);
+  in.setRandom();
+
+  Tensor<std::complex<float>, 0> full_redux;
+  full_redux = in.mean();
+
+  std::size_t in_bytes = in.size() * sizeof(std::complex<float>);
+  std::size_t out_bytes = full_redux.size() * sizeof(std::complex<float>);
+  std::complex<float>* gpu_in_ptr = static_cast<std::complex<float>*>(gpu_device.allocate(in_bytes));
+  std::complex<float>* gpu_out_ptr = static_cast<std::complex<float>*>(gpu_device.allocate(out_bytes));
+  gpu_device.memcpyHostToDevice(gpu_in_ptr, in.data(), in_bytes);
+
+  TensorMap<Tensor<std::complex<float>, 2> > in_gpu(gpu_in_ptr, num_rows, num_cols);
+  TensorMap<Tensor<std::complex<float>, 0> > out_gpu(gpu_out_ptr);
+
+  out_gpu.device(gpu_device) = in_gpu.mean();
+
+  Tensor<std::complex<float>, 0> full_redux_gpu;
+  gpu_device.memcpyDeviceToHost(full_redux_gpu.data(), gpu_out_ptr, out_bytes);
+  gpu_device.synchronize();
+
+  // Check that the CPU and GPU reductions return the same result.
+  VERIFY_IS_APPROX(full_redux(), full_redux_gpu());
+
+  gpu_device.deallocate(gpu_in_ptr);
+  gpu_device.deallocate(gpu_out_ptr);
+}
 
 static void test_cuda_product_reductions() {
 
@@ -149,5 +184,6 @@ void test_cxx11_tensor_complex()
 {
   CALL_SUBTEST(test_cuda_nullary());
   CALL_SUBTEST(test_cuda_sum_reductions());
+  CALL_SUBTEST(test_cuda_mean_reductions());
   CALL_SUBTEST(test_cuda_product_reductions());
 }
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