java.lang.NoSuchMethodError while running Mahout example

Yesterday I was setting up Apache Mahout for work related stuff. After downloading, unzipping and untarring I installed using  –
(version 0.7, 0.8 and 0.9 [trunk] all gave the same issue which I am addressing in this post)

mvn -DskipTests clean install

After setting up some environment variables like MAHOUT_HOME I was ready to go for running some machine learning algorithms on some data. I chose Quick Start Guide on the Mahout site. I downloaded the sample data, copied it to Hadoop (cloudera distribution 4.3.0 cdh4) HDFS as instructed on the quick start page. After this, I ran kMeans algorithm on the sample data copied in HDFS:

$MAHOUT_HOME/bin/mahout org.apache.mahout.clustering.syntheticcontrol.kmeans.Job

It failed with following error:

Exception in thread “main” java.lang.NoSuchMethodError:
org.apache.hadoop.util.ProgramDriver.driver([Ljava/lang/String;)V
at org.apache.mahout.driver.MahoutDriver.main(MahoutDriver.java:175)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.util.RunJar.main(RunJar.java:192)*

I searched on Google and found many many many results. All pointing to some kind of version mismatch between Hadoop and Mahout OR some issue with CLASSPATH or some thing else. I could not really resolve the issue since was not flexible to change the version of Hadoop and was receiving this error for Mahout v0.7, 0.8 and svn trunk (0.9).

Finally, I ran the algorithm like this (replacing `bin/mahout` with `hadoop -jar apache-mahout-version-job.jar.. `)

$HADOOP_HOME/bin/hadoop -jar $MAHOUT_HOME/examples/target/apache-mahout-0.7-job.jar org.apache.mahout.clustering.syntheticcontrol.kmeans.Job

And this worked.

Looks like a classpath issue. Hadoop was not able to get access to Mahout 0.7 job JAR file and hence was throwing NoSuchMethodError. I didn’t have much progress resolving the CLASSPATH issue but was happy to get the map-reduce job running and getting the output which I finally copied back to file system.

BTW – this alternative is equivalent of running mahout shell script – so not that you miss anything.

Also note that if you are using Mahout version 0.7 – there is a bug in the script $MAHOUT_HOME/bin/mahout at line number 224 (around that) – read this:

> bin/mahout throws NoClassDefFoundError: org/apache/hadoop/util/ProgramDriver
> I think this is due to line 224
> CLASSPATH=”${CLASSPATH}:${MAHOUT_HOME/lib/hadoop/*}”
> I fix the issue by moving the closing brace
> CLASSPATH=”${CLASSPATH}:${MAHOUT_HOME}/lib/hadoop/*”

You can fix it locally. This issue is fixed in 0.8.

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Writing “Hello World” program!

Sometimes we get questions which are silliest but have to attempt since the situation demands it (interviews, presentations, professor’s lecture..). One of those silly (of almost “0” importance and usability in life) questions is “How many ways can you write a ‘Hello, World!’ program in C/C++?”.

For those, who want me to write some specification of the program – task is to write a program to print on console a string “Hello, World!”. Well, lots and lots of answers —

int main() { printf(“Hello, World!\n”); } /* C Example */

int main() { std::cout << “Hello, World!” << endl; } // C++ Example

int main() { if(printf(“Hello, World!\n”)) {} } // C; without semicolon

int main() { while(!printf(“Hello, World!\n”)) {} } // C; without semicolon

following, I came through while re-reading stroustrup is writing a program using iterators (Chapter3;Iterators and I/O). This is nothing new and just a iteratorized manifestation of example II above.. but yes, different clothing!

ostream_iterator<string> oo(cout);
int main() { *oo = “Hello, “; ++oo; *oo = “World!\n”; }