Minor Description
Support NullWritable in Hama Pipes
It should be possible to read, write and send NullWritables in Hama Pipes.
Therefore the void type is supported in C++ templates.
e.g., PiEstimator (InputKeyClass, InputValueClass and OutputKeyClass are NullWritables)
-class PiEstimatorBSP: public BSP<string,string,string,double,int> { +class PiEstimatorBSP: public BSP<void,void,void,double,int> { ... - void cleanup(BSPContext<string,string,string,double,int>& context) { + void cleanup(BSPContext<void,void,void,double,int>& context) { ... double pi = 4.0 * total_hits / (msg_count * iterations_); - context.write("Estimated value of PI", pi); + context.write(pi); } }
This is affecting the following C++ methods:
- Input
bool readNext(K1& key, V1& value)
method is available at compile time if BSP<K1!=void, V1!=void, ?, ?, ?> bool readNext(K1& key)
method is available at compile time if BSP<K1!=void, V1==void, ?, ?, ?> bool readNext(V1& value)
method is available at compile time if BSP<K1==void, V1!=void, ?, ?, ?> method will not be available at compile time if BSP<K1==void, V1==void, ?, ?, ?>
- Output
void write(const K2& key, const V2& value)
method is available at compile time if BSP<?, ?, K2!=void, V2!=void, ?> void write(const K2& key)method is available at compile time if BSP<?, ?, K2!=void, V2==void, ?> void write(const V2& value)method is available at compile time if BSP<?, ?, K2==void, V2!=void, ?> method will not be available at compile time if BSP<?, ?, K2==void, V2==void, ?>
- Message
void sendMessage(const string& peerName, const M& msg)
method will not be available at compile time if BSP<?, ?, ?, ?, M==void> M getCurrentMessage()
method will not be available at compile time if BSP<?, ?, ?, ?, M==void>
Hama Pipes supports NullWritables in SequenceFileInputFormat and SequenceFileOutputFormat.
The same is valid for the SequenceFile methods:
- SequenceFile.Reader
bool sequenceFileReadNext<K, V>(int fileID, K& key, V& value)method is available at compile time if <K!=void, V!=void> bool sequenceFileReadNext<K>(int fileID, K& key)method is available at compile time if <K!=void> bool sequenceFileReadNext<V>(int fileID, V& value)method is available at compile time if <V!=void>
- SequenceFile.Writer
bool sequenceFileAppend<K, V>(int fileID, const K& key, const V& value)
method is available at compile time if <K!=void, V!=void> bool sequenceFileAppend<K>(int fileID, K& key)method is available at compile time if <K!=void> bool sequenceFileAppend<V>(int fileID, V& value)method is available at compile time if <V!=void>