add hadoop linear example

rabit-learn/linear/run-hadoop.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+if [ "$#" -lt 3 ];
+then
+	echo "Usage: <nworkers> <path_in_HDFS> [param=val]"
+	exit -1
+fi
+
+# put the local training file to HDFS
+hadoop fs -rm -r -f $2/data
+hadoop fs -rm -r -f $2/mushroom.linear.model
+hadoop fs -mkdir $2/data
+hadoop fs -put ../data/agaricus.txt.train $2/data
+
+# submit to hadoop
+../../tracker/rabit_hadoop.py  -n $1 -i $2/data/agaricus.txt.train -o $2/mushroom.linear.model linear.rabit stdin model_out=stdout "${*:3}" 
+
+# get the final model file
+hadoop fs -get $2/mushroom.linear.model/part-00000 ./linear.model
+
+./linear.rabit ../data/agaricus.txt.test task=pred model_in=linear.model