Fix scan by key docs for in-place execution

Author: gevtushenko

Diff for: testing/cuda/scan_by_key.cu

@@ -78,7 +78,7 @@ void TestScanByKeyDevice(ExecutionPolicy exec)
   }
   ASSERT_EQUAL(d_output, h_output);
 
-  // in-place scans
+  // in-place scans: in/out values aliasing
   h_output = h_vals;
   d_output = d_vals;
   thrust::inclusive_scan_by_key(h_keys.begin(), h_keys.end(), h_output.begin(), h_output.begin());
@@ -98,6 +98,24 @@ void TestScanByKeyDevice(ExecutionPolicy exec)
     ASSERT_EQUAL(cudaSuccess, err);
   }
   ASSERT_EQUAL(d_output, h_output);
+
+  // in-place scans: keys/values aliasing
+  thrust::inclusive_scan_by_key(h_keys.begin(), h_keys.end(), h_vals.begin(), h_output.begin());
+  inclusive_scan_by_key_kernel<<<1,1>>>(exec, d_keys.begin(), d_keys.end(), d_vals.begin(), d_keys.begin());
+  {
+    cudaError_t const err = cudaDeviceSynchronize();
+    ASSERT_EQUAL(cudaSuccess, err);
+  }
+  ASSERT_EQUAL(d_keys, h_output);
+
+  d_keys = h_keys;
+  thrust::exclusive_scan_by_key(h_keys.begin(), h_keys.end(), h_vals.begin(), h_output.begin(), 11);
+  exclusive_scan_by_key_kernel<<<1,1>>>(exec, d_keys.begin(), d_keys.end(), d_vals.begin(), d_keys.begin(), 11);
+  {
+    cudaError_t const err = cudaDeviceSynchronize();
+    ASSERT_EQUAL(cudaSuccess, err);
+  }
+  ASSERT_EQUAL(d_keys, h_output);
 }