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From "Edward J. Yoon (JIRA)" <j...@apache.org>
Subject [jira] Created: (HAMA-190) Bug in Matrix-Vector multiplication
Date Thu, 10 Sep 2009 01:39:57 GMT
Bug in Matrix-Vector multiplication
-----------------------------------

                 Key: HAMA-190
                 URL: https://issues.apache.org/jira/browse/HAMA-190
             Project: Hama
          Issue Type: Bug
          Components: implementation
    Affects Versions: 0.1.0
            Reporter: Edward J. Yoon
            Assignee: Edward J. Yoon
             Fix For: 0.1.0


Hi again,

Since I've more complex operations, (such as multiply, inverse, load...) I decided coding
instead of use the shell.

I've wrote simple example to multiple 2 matrixes, and got incorrect results, can you let me
know if I've some mistake, or it's well known bug.

A =     1,2
       3,4

B =     1
       2

The result should be (C = A * B):
C =     5
       11

But I got incorrect results from the example below:
1.0,2.0
3.0,6.0

The code:

public static void main(String[] args) throws IOException {

       conf.set("hbase.rootdir", "hdfs://lb-emu-2:54310/hbase");
       conf.set("hbase.master", "lb-emu-2:60000");
       conf.set("mapred.jar", "/app/installs/hama/hama-0.1.0-dev.jar");

       DenseMatrix a = new DenseMatrix(conf, "A", true);

       a.setDimension(2, 2);
       a.set(0, 0, 1);
       a.set(0, 1, 2);
       a.set(1, 0, 3);
       a.set(1, 1, 4);

       DenseMatrix b = new DenseMatrix(conf, "B", true);

       b.setDimension(2, 1);
       b.set(0, 0, 1);
       b.set(0, 1, 2);

       DenseMatrix c = a.mult(b);

       for (int i = 0; i < c.getRows(); i++) {
           for (int j = 0; j < c.getColumns(); j++) {
               System.out.print(c.get(i, j) + " ");
           }
           System.out.println("");
       }
   }


Thanks again,
Nir.

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