Github #273 Handle failure to initialise BackendContext in Runtime

Define CreateBackendContext to throw BackendUnavailableException
if necessary runtime components are missing.

Handle this in the constructor of Runtime by not adding those
backends to the internal DeviceSpec owned by the Runtime.

Signed-off-by: Matthew Bentham <Matthew.Bentham@arm.com>
Change-Id: Iadffb5240e32e1f105683c4d361276b92d1e720c

1 files changed, 9 insertions, 4 deletions

diff --git a/src/armnn/Runtime.cpp b/src/armnn/Runtime.cpp
index 2d7269a09c..47c998a6fd 100644
--- a/src/armnn/Runtime.cpp
+++ b/src/armnn/Runtime.cpp
@@ -153,7 +153,6 @@ const std::shared_ptr<IProfiler> Runtime::GetProfiler(NetworkId networkId) const
 
 Runtime::Runtime(const CreationOptions& options)
     : m_NetworkIdCounter(0)
-    , m_DeviceSpec{BackendRegistryInstance().GetBackendIds()}
 {
     ARMNN_LOG(info) << "ArmNN v" << ARMNN_VERSION << "\n";
 
@@ -164,12 +163,11 @@ Runtime::Runtime(const CreationOptions& options)
     // goes through the backend registry
     LoadDynamicBackends(options.m_DynamicBackendsPath);
 
+    BackendIdSet supportedBackends;
     for (const auto& id : BackendRegistryInstance().GetBackendIds())
     {
         // Store backend contexts for the supported ones
-        const BackendIdSet& supportedBackends = m_DeviceSpec.GetSupportedBackends();
-        if (supportedBackends.find(id) != supportedBackends.end())
-        {
+        try {
             auto factoryFun = BackendRegistryInstance().GetFactory(id);
             auto backend = factoryFun();
             BOOST_ASSERT(backend.get() != nullptr);
@@ -182,8 +180,15 @@ Runtime::Runtime(const CreationOptions& options)
             {
                 m_BackendContexts.emplace(std::make_pair(id, std::move(context)));
             }
+            supportedBackends.emplace(id);
+        }
+        catch (const BackendUnavailableException&)
+        {
+            // Ignore backends which are unavailable
         }
+
     }
+    m_DeviceSpec.AddSupportedBackends(supportedBackends);
 }
 
 Runtime::~Runtime()