Add transform_output_iterator and transform_input_output_iterator default constructors

testing/CMakeLists.txt

@@ -41,6 +41,10 @@ thrust_declare_test_restrictions(future            CPP.CUDA OMP.CUDA TBB.CUDA)
 # for CUDA.
 thrust_declare_test_restrictions(unittest_static_assert CPP.CPP CPP.CUDA)
 
+# In the TBB backend, reduce_by_key does not currently work with transform_output_iterator
+# https://github.com/NVIDIA/thrust/issues/1811
+thrust_declare_test_restrictions(transform_output_iterator_reduce_by_key CPP.CPP CPP.OMP CPP.CUDA)
+
 ## thrust_add_test
 #
 # Add a test executable and register it with ctest.

testing/transform_output_iterator.cu

@@ -1,11 +1,13 @@
 #include <unittest/unittest.h>
-#include <thrust/iterator/transform_output_iterator.h>
 
 #include <thrust/copy.h>
-#include <thrust/reduce.h>
+#include <thrust/device_vector.h>
 #include <thrust/functional.h>
-#include <thrust/sequence.h>
+#include <thrust/host_vector.h>
 #include <thrust/iterator/counting_iterator.h>
+#include <thrust/iterator/transform_output_iterator.h>
+#include <thrust/reduce.h>
+#include <thrust/sequence.h>
 
 template <class Vector>
 void TestTransformOutputIterator(void)

testing/transform_output_iterator_reduce_by_key.cu

@@ -0,0 +1,51 @@
+#include <unittest/unittest.h>
+
+#include <thrust/copy.h>
+#include <thrust/device_vector.h>
+#include <thrust/functional.h>
+#include <thrust/host_vector.h>
+#include <thrust/iterator/counting_iterator.h>
+#include <thrust/iterator/discard_iterator.h>
+#include <thrust/iterator/transform_output_iterator.h>
+#include <thrust/reduce.h>
+#include <thrust/sequence.h>
+#include <thrust/sort.h>
+
+
+template <typename T>
+struct TestTransformOutputIteratorReduceByKey
+{
+  void operator()(const size_t n)
+  {
+    thrust::host_vector<T> h_keys = unittest::random_samples<T>(n);
+    thrust::sort(h_keys.begin(), h_keys.end());
+    thrust::device_vector<T> d_keys = h_keys;
+
+    thrust::host_vector<T> h_values   = unittest::random_samples<T>(n);
+    thrust::device_vector<T> d_values = h_values;
+
+    thrust::host_vector<T> h_result(n);
+    thrust::device_vector<T> d_result(n);
+
+    // run on host
+    thrust::reduce_by_key(thrust::host,
+                          h_keys.begin(),
+                          h_keys.end(),
+                          thrust::make_transform_iterator(h_values.begin(), thrust::negate<T>()),
+                          thrust::discard_iterator<T>{},
+                          h_result.begin());
+    // run on device
+    thrust::reduce_by_key(thrust::device,
+                          d_keys.begin(),
+                          d_keys.end(),
+                          d_values.begin(),
+                          thrust::discard_iterator<T>{},
+                          thrust::make_transform_output_iterator(d_result.begin(),
+                                                                 thrust::negate<T>()));
+
+    ASSERT_EQUAL(h_result, d_result);
+  }
+};
+VariableUnitTest<TestTransformOutputIteratorReduceByKey, SignedIntegralTypes>
+  TestTransformOutputIteratorReduceByKeyInstance;
+

thrust/iterator/transform_input_output_iterator.h

@@ -102,6 +102,8 @@ template <typename InputFunction, typename OutputFunction, typename Iterator>
   /*! \endcond
    */
 
+  transform_input_output_iterator() = default;
+
   /*! This constructor takes as argument a \c Iterator an \c InputFunction and an
    * \c OutputFunction and copies them to a new \p transform_input_output_iterator
    *

thrust/iterator/transform_output_iterator.h

@@ -104,6 +104,8 @@ template <typename UnaryFunction, typename OutputIterator>
   /*! \endcond
    */
 
+  transform_output_iterator() = default;
+
   /*! This constructor takes as argument an \c OutputIterator and an \c
    * UnaryFunction and copies them to a new \p transform_output_iterator
    *