[HAMA-190] Bug in Matrix-Vector multiplication

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Component/s: math
• Assignee: Edward J. Yoon
• Reporter: Edward J. Yoon
• Created: 10/Sep/09 01:38
• Updated: 08/Jun/11 09:32
• Resolved: 21/Oct/09 05:12

Description

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.