Martin Illecker created MAHOUT-1266:
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             Summary: Two minor problems in DistributedRowMatrix using 
MatrixMultiplication
                 Key: MAHOUT-1266
                 URL: https://issues.apache.org/jira/browse/MAHOUT-1266
             Project: Mahout
          Issue Type: Bug
          Components: Math
    Affects Versions: 0.7
            Reporter: Martin Illecker
            Priority: Trivial


Hello,

I think I have found two minor problems in *DistributedRowMatrix*.

In [1] the condition is wrong, because (l x m) * (m x n) = (l x n).
The condition should be like in [2]. 

And in *times*[3] the {{this.transpose()}} seems to be missing? (See [4])

Do you have any benchmark results for Mahout MatrixMultiplication?

Thanks!

Martin

[1|https://github.com/apache/mahout/blob/trunk/core/src/main/java/org/apache/mahout/math/hadoop/DistributedRowMatrix.java#L191-193]
[2|https://github.com/millecker/applications/blob/master/hadoop/rootbeer/matrixmultiplication/src/at/illecker/hadoop/rootbeer/examples/matrixmultiplication/DistributedRowMatrix.java#L222-226]
[3|https://github.com/apache/mahout/blob/trunk/core/src/main/java/org/apache/mahout/math/hadoop/DistributedRowMatrix.java#L190-206]
[4|https://github.com/millecker/applications/blob/master/hadoop/rootbeer/matrixmultiplication/src/at/illecker/hadoop/rootbeer/examples/matrixmultiplication/DistributedRowMatrix.java#L231-232]



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