[HAMA-151] Add multiplication example of file matrices

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Component/s: documentation , examples
• Assignee: Edward J. Yoon
• Reporter: Edward J. Yoon
• Created: 11/Feb/09 09:53
• Updated: 08/Jun/11 09:31
• Resolved: 12/Feb/09 04:23

Description

Using CollectBlocksMap (See also HAMA-150), We can collect the blocks to 'collectionTable' from HDFS files as describe below.
It would be nice if it added up the examples.

---

public static class MyMapper extends CollectBlocksBase implements
CollectBlocksMap<IntWritable, MapWritable> {
private MapWritable value;

@Override
public void map(IntWritable key, MapWritable value,
OutputCollector<BlockID, VectorWritable> output, Reporter reporter)
throws IOException {
int startColumn;
int endColumn;
int blkRow = key.get() / mBlockRowSize;
this.value = value;

int i = 0;
do

{ startColumn = i * mBlockColSize; endColumn = startColumn + mBlockColSize - 1; if (endColumn >= mColumns) // the last sub vector endColumn = mColumns - 1; output.collect(new BlockID(blkRow, i), new VectorWritable(key.get(), subVector(startColumn, endColumn))); i++; }

while (endColumn < (mColumns - 1));
}

private DenseVector subVector(int i0, int i1) {
DenseVector res = new DenseVector();
for (int i = i0; i <= i1; i++)

{ res.set(i, ((DoubleWritable) this.value.get(new IntWritable(i))).get()); }

return res;
}
}