Merge pull request #121 from ldmoser/recomputationBug

Bug fix: preventing a Computation result to be recomputed everytime

Author: johnhaddon

include/IECore/ComputationCache.inl

@@ -35,6 +35,8 @@
 #ifndef IECORE_COMPUTATIONCACHE_INL
 #define IECORE_COMPUTATIONCACHE_INL
 
+#include "IECore/MessageHandler.h"
+
 namespace IECore
 {
 
@@ -123,6 +125,13 @@ ConstObjectPtr ComputationCache<T>::get( const T &args, ComputationCache::Missin
 			if ( obj )
 			{
 				obj = m_objectPool->store( obj, ObjectPool::StoreReference );
+				MurmurHash h = obj->hash();
+				if ( h != objectHash )
+				{
+					/// the computation returned a different object for some reason, so we have to update the hash
+					m_cache.set( computationHash, h, 1 );	
+					msg( Msg::Warning, "ComputationCache::get", "Inconsistent hash detected." );
+				}
 			}
 		}
 	}

test/IECore/ComputationCacheTest.cpp

@@ -51,6 +51,7 @@ namespace IECore
 struct ComputationCacheTest
 {
 
+	static int getCount;
 	typedef int ComputationParams;
 	typedef ComputationCache< ComputationParams > Cache;
 
@@ -65,6 +66,7 @@ struct ComputationCacheTest
 	static IntDataPtr get( const ComputationParams &params )
 	{
 		int id = params;
+		getCount++;
 		return new IntData( id );
 	}
 
@@ -150,6 +152,23 @@ struct ComputationCacheTest
 		v->writable() = 42;
 		BOOST_CHECK( *v != *cache.get( ComputationParams(1), Cache::NullIfMissing ) );
 
+		// test when the computation function does not match the already registered computation hash....
+		IntDataPtr weirdValue = new IntData(666);
+		cache.clear();
+		cache.set( ComputationParams(1), weirdValue, ObjectPool::StoreReference );
+		ConstObjectPtr v0 = cache.get( ComputationParams(1) );
+		BOOST_CHECK( *weirdValue == *cache.get( ComputationParams(1), Cache::NullIfMissing ) );
+		pool->clear();
+		int c1 = ComputationCacheTest::getCount;
+		ConstObjectPtr v1 = cache.get( ComputationParams(1) );
+		int c2 = ComputationCacheTest::getCount;
+		BOOST_CHECK_EQUAL( 1, static_cast< const IntData * >(v1.get())->readable() );
+		BOOST_CHECK_EQUAL( c1 + 1, c2 );
+		ConstObjectPtr v2 = cache.get( ComputationParams(1) );
+		int c3 = ComputationCacheTest::getCount;
+		BOOST_CHECK_EQUAL( 1, static_cast< const IntData * >(v2.get())->readable() );
+		/// garantee that there was no recomputation.
+		BOOST_CHECK_EQUAL( c2, c3 );
 	}
 
 	struct GetFromCache
@@ -192,6 +211,7 @@ struct ComputationCacheTest
 
 };
 
+int ComputationCacheTest::getCount(0);
 
 struct ComputationCacheTestSuite : public boost::unit_test::test_suite
 {