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http://wiki.apache.org/hama/Architecture

 Reduce task select the maximum one
}}}
+ === Compute the infinity norm ===
+
+ It's a maximum absolute column sum of matrix.
+
+ {{{
+ i=n
+ The maximum absolute column sum = max ( sum  a_{i,j}  )
+ 1<=j<=n i=1
+
+  A map task receives a row n as a key, and vector of each row as its value
+  emit (column, the absolute value of each entries)
+  Reduce task sum the absolute values of column, select the one maximum one.
+ }}}
+
=== Compute the transpose of a matrix ===
The transpose of a matrix is another matrix in which the rows and columns have been reversed.
The matrix must be square for this work.
