= 2010-05-10 =

== Hadoop : Matrix Multiply 用 MapReduce 作矩陣運算 ==

 * 測試 [http://homepage.mac.com/j.norstad/matrix-multiply/index.html A MapReduce Algorithm for Matrix Multiplication] 所提供之矩陣相乘範例
   * 發現會有 IOException 錯誤訊息，肇因於 /tmp/MatrixMultiply/out/_logs 是目錄而不是檔案
{{{
10/05/10 15:23:23 INFO input.FileInputFormat: Total input paths to process : 1
10/05/10 15:23:23 INFO mapred.JobClient: Running job: job_201005101012_0016
10/05/10 15:23:24 INFO mapred.JobClient:  map 0% reduce 0%
10/05/10 15:23:33 INFO mapred.JobClient:  map 100% reduce 0%
10/05/10 15:23:45 INFO mapred.JobClient:  map 100% reduce 100%
10/05/10 15:23:47 INFO mapred.JobClient: Job complete: job_201005101012_0016
..........
Exception in thread "main" java.io.IOException: Cannot open filename /tmp/MatrixMultiply/out/_logs
        at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.openInfo(DFSClient.java:1497)
}}}
   * [解法] 修改 !TestMatrixMultiply.java，並以單機 !LocalRunner 執行。( hadoop 0.20.2 預設用 !LocalRunner )
{{{
jazz@drbl:~$ wget http://ftp.twaren.net/Unix/Web/apache/hadoop/core/hadoop-0.20.2/hadoop-0.20.2.tar.gz
jazz@drbl:~$ tar zxvf hadoop-0.20.2.tar.gz
jazz@drbl:~$ cd hadoop-0.20.2
jazz@drbl:~/hadoop-0.20.2$ echo "export JAVA_HOME=/usr/lib/jvm/java-6-sun/" >> conf/hadoop-env.sh
jazz@drbl:~/hadoop-0.20.2$ wget http://trac.nchc.org.tw/grid/raw-attachment/wiki/jazz/10-05-10/matrix.tar.gz
jazz@drbl:~/hadoop-0.20.2$ tar zxvf matrix.tar.gz
jazz@drbl:~/hadoop-0.20.2$ cd matrix/
jazz@drbl:~/hadoop-0.20.2/matrix$ ant
jazz@drbl:~/hadoop-0.20.2/matrix$ mv matrix.jar ../.
jazz@drbl:~/hadoop-0.20.2/matrix$ cd ..
jazz@drbl:~/hadoop-0.20.2$ bin/hadoop jar matrix.jar TestMatrixMultiply
}}}
{{{
--- source/TestMatrixMultiply.java      2009-12-12 23:00:03.000000000 +0800
+++ matrix/src/TestMatrixMultiply.java  2010-05-11 00:25:02.000000000 +0800
@@ -72,13 +72,11 @@
                for (int i = 0; i < rowDim; i++)
                        for (int j = 0; j < colDim; j++)
                                result[i][j] = 0;
-               if (fs.isFile(path)) {
-                       fillMatrix(result, path);
-               } else {
-                       FileStatus[] fileStatusArray = fs.listStatus(path);
-                       for (FileStatus fileStatus : fileStatusArray) {
-                               fillMatrix(result, fileStatus.getPath());
-                       }
+               FileStatus[] fileStatusArray = fs.listStatus(path);
+               for (FileStatus fileStatus : fileStatusArray) {
+                 if (fs.isFile(fileStatus.getPath())) {
+                   fillMatrix(result, fileStatus.getPath());
+                 }
                }
                return result;
        }
@@ -100,10 +98,13 @@
        public static void checkAnswer (int[][] A, int[][] B, int I, int K, int J)
                throws Exception
        {
+               System.out.println("......multiply(...)");
                int[][] X = multiply(A, B, I, K, J);
+               System.out.println("......readMatrix("+I+","+J+","+OUTPUT_DIR_PATH);
                int[][] Y = readMatrix(I, J, OUTPUT_DIR_PATH);
                for (int i = 0; i < I; i++) {
                        for (int j = 0; j < J; j++) {
+                               System.out.println("......X["+i+"]["+j+"]="+X[i][j]+", Y["+i+"]["+j+"]="+Y[i][j]);
                                if (X[i][j] != Y[i][j]) {
                                        throw new Exception("Bad answer!");
                                }
@@ -135,8 +136,10 @@
                int IB, int KB, int JB)
                        throws Exception
        {
+               System.out.println("...MatrixMultiply.runJob(...)");
                MatrixMultiply.runJob(conf, INPUT_PATH_A, INPUT_OATH_B, OUTPUT_DIR_PATH, TEMP_DIR_PATH,
                        strategy, R1, R2, I, K, J, IB, KB, JB);
+               System.out.println("...checkAnswer(...)");
                checkAnswer(A, B, I, K, J);
        }

@@ -279,8 +282,8 @@
                        System.out.println("================");
                        System.out.println();
                } finally {
-                       fs.delete(new Path(DATA_DIR_PATH), true);
+                       //fs.delete(new Path(DATA_DIR_PATH), true);
                }
        }
}}}