Upstream a number of changes to git.

Changes:
- Updates to README / os_setup for common installation issues
  by ebrevdo, vrv, wicke, anelia, dga

- Add a test for backwards compatibility checks by Josh

- Simplifications to tiling/padding of scalars by bsteiner

- Improve listing of devices when no devices are known by Matthieu

Base CL: 107607137

1 files changed, 5 insertions, 1 deletions

diff --git a/tensorflow/core/common_runtime/local_session.cc b/tensorflow/core/common_runtime/local_session.cc
index ab6993b8a2..4c41e5b3b3 100644
--- a/tensorflow/core/common_runtime/local_session.cc
+++ b/tensorflow/core/common_runtime/local_session.cc
@@ -103,7 +103,11 @@ LocalSession::LocalSession(const SessionOptions& options,
   int devices_added = 0;
   if (options.config.log_device_placement()) {
     const string mapping_str = device_mgr_->DeviceMappingString();
-    printf("Device mapping:\n%s", mapping_str.c_str());
+    if (mapping_str.empty()) {
+      printf("Device mapping: no known devices.\n");
+    } else {
+      printf("Device mapping:\n%s", mapping_str.c_str());
+    }
     LOG(INFO) << "Device mapping:\n" << mapping_str;
   }
   for (auto d : device_mgr_->ListDevices()) {