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Posted to dev@mahout.apache.org by "liutengfei (JIRA)" <ji...@apache.org> on 2012/09/27 03:21:07 UTC
[jira] [Created] (MAHOUT-1083) CIReducer in kmeans doesn't work
well
liutengfei created MAHOUT-1083:
----------------------------------
Summary: CIReducer in kmeans doesn't work well
Key: MAHOUT-1083
URL: https://issues.apache.org/jira/browse/MAHOUT-1083
Project: Mahout
Issue Type: Bug
Environment: hadoop-2.0.0-alpha: pseudo cluster and single node cluster hadoop-1.0.3: pseudo cluster hadoop-0.20.2:pseudo cluster mahout: mahout-0.7 os: ubuntu 11.04 jdk: jdk1.6.0_27
Reporter: liutengfei
the function "reduce" in mahout-0.7-kmeans-CIReducer.java doesn't work well as it looks like.
protected void reduce(IntWritable key, Iterable<ClusterWritable> values, Context context) throws IOException,
InterruptedException {
Iterator<ClusterWritable> iter = values.iterator();
ClusterWritable first = null;
while (iter.hasNext()) {
ClusterWritable cw = iter.next();
if (first == null) {
first = cw;
} else {
first.getValue().observe(cw.getValue());
}
}
List<Cluster> models = new ArrayList<Cluster>();
models.add(first.getValue());
classifier = new ClusterClassifier(models, policy);
classifier.close();
context.write(key, first);
}
Apparently， the variable "first" will collect all output data of maps. Actually but, the value of "first" will change after the code "ClusterWritable cw = iter.next();", same with this new variable "cw"! I don't why but running result shows that the code runs looks like this:"ClusterWritable cw = first = iter.next();".
is "cw" a reference a to "iter"?
is "iter.next" just change the value of "iter" itself to the next?
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[jira] [Updated] (MAHOUT-1083) CIReducer in kmeans doesn't work
well
Posted by "Jeff Eastman (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAHOUT-1083?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jeff Eastman updated MAHOUT-1083:
---------------------------------
Attachment: MAHOUT-1083.patch
Oh Yikes! This is another example of the Hadoop platform reusing a single instance of the Writable every time another one is read from the input stream. Every time iter.next() is called, the same object (cw == first) will be returned. This does not show up in unit tests because only a single reducer is ever used. It explains exactly the odd clustering behavior you have observed.
Here's a patch that *may* fix the problem. I believe that ClusterWritable will create a new instance for its value instVar even if the same ClusterWritable is used.
Please try this and see if it resolves the issue.
> CIReducer in kmeans doesn't work well
> -------------------------------------
>
> Key: MAHOUT-1083
> URL: https://issues.apache.org/jira/browse/MAHOUT-1083
> Project: Mahout
> Issue Type: Bug
> Environment: hadoop-2.0.0-alpha: pseudo cluster and single node cluster hadoop-1.0.3: pseudo cluster hadoop-0.20.2:pseudo cluster mahout: mahout-0.7 os: ubuntu 11.04 jdk: jdk1.6.0_27
> Reporter: liutengfei
> Attachments: MAHOUT-1083.patch
>
>
> the function "reduce" in mahout-0.7-kmeans-CIReducer.java doesn't work well as it looks like.
> protected void reduce(IntWritable key, Iterable<ClusterWritable> values, Context context) throws IOException,
> InterruptedException {
> Iterator<ClusterWritable> iter = values.iterator();
> ClusterWritable first = null;
> while (iter.hasNext()) {
> ClusterWritable cw = iter.next();
> if (first == null) {
> first = cw;
> } else {
> first.getValue().observe(cw.getValue());
> }
> }
> List<Cluster> models = new ArrayList<Cluster>();
> models.add(first.getValue());
> classifier = new ClusterClassifier(models, policy);
> classifier.close();
> context.write(key, first);
> }
> Apparently， the variable "first" will collect all output data of maps. Actually but, the value of "first" will change after the code "ClusterWritable cw = iter.next();", same with this new variable "cw"! I don't why but running result shows that the code runs looks like this:"ClusterWritable cw = first = iter.next();".
> is "cw" a reference a to "iter"?
> is "iter.next" just change the value of "iter" itself to the next?
--
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[jira] [Commented] (MAHOUT-1083) CIReducer in kmeans doesn't work
well
Posted by "liutengfei (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAHOUT-1083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13465496#comment-13465496 ]
liutengfei commented on MAHOUT-1083:
------------------------------------
it works, thanks a lot.
> CIReducer in kmeans doesn't work well
> -------------------------------------
>
> Key: MAHOUT-1083
> URL: https://issues.apache.org/jira/browse/MAHOUT-1083
> Project: Mahout
> Issue Type: Bug
> Environment: hadoop-2.0.0-alpha: pseudo cluster and single node cluster hadoop-1.0.3: pseudo cluster hadoop-0.20.2:pseudo cluster mahout: mahout-0.7 os: ubuntu 11.04 jdk: jdk1.6.0_27
> Reporter: liutengfei
> Attachments: MAHOUT-1083.patch
>
>
> the function "reduce" in mahout-0.7-kmeans-CIReducer.java doesn't work well as it looks like.
> protected void reduce(IntWritable key, Iterable<ClusterWritable> values, Context context) throws IOException,
> InterruptedException {
> Iterator<ClusterWritable> iter = values.iterator();
> ClusterWritable first = null;
> while (iter.hasNext()) {
> ClusterWritable cw = iter.next();
> if (first == null) {
> first = cw;
> } else {
> first.getValue().observe(cw.getValue());
> }
> }
> List<Cluster> models = new ArrayList<Cluster>();
> models.add(first.getValue());
> classifier = new ClusterClassifier(models, policy);
> classifier.close();
> context.write(key, first);
> }
> Apparently， the variable "first" will collect all output data of maps. Actually but, the value of "first" will change after the code "ClusterWritable cw = iter.next();", same with this new variable "cw"! I don't why but running result shows that the code runs looks like this:"ClusterWritable cw = first = iter.next();".
> is "cw" a reference a to "iter"?
> is "iter.next" just change the value of "iter" itself to the next?
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[jira] [Commented] (MAHOUT-1083) CIReducer in kmeans doesn't work
well
Posted by "Hudson (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAHOUT-1083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13466137#comment-13466137 ]
Hudson commented on MAHOUT-1083:
--------------------------------
Integrated in Mahout-Quality #1678 (See [https://builds.apache.org/job/Mahout-Quality/1678/])
MAHOUT-1083:
- committed patch to CIReducer that was producing odd results
- changed test count from 3 to 4 to cause mean shift test to pass
- all tests now run again (Revision 1391752)
Result = SUCCESS
jeastman : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1391752
Files :
* /mahout/trunk/core/src/main/java/org/apache/mahout/clustering/iterator/CIReducer.java
* /mahout/trunk/core/src/main/java/org/apache/mahout/clustering/iterator/ClusterWritable.java
* /mahout/trunk/core/src/test/java/org/apache/mahout/clustering/meanshift/TestMeanShift.java
> CIReducer in kmeans doesn't work well
> -------------------------------------
>
> Key: MAHOUT-1083
> URL: https://issues.apache.org/jira/browse/MAHOUT-1083
> Project: Mahout
> Issue Type: Bug
> Environment: hadoop-2.0.0-alpha: pseudo cluster and single node cluster hadoop-1.0.3: pseudo cluster hadoop-0.20.2:pseudo cluster mahout: mahout-0.7 os: ubuntu 11.04 jdk: jdk1.6.0_27
> Reporter: liutengfei
> Attachments: MAHOUT-1083.patch
>
>
> the function "reduce" in mahout-0.7-kmeans-CIReducer.java doesn't work well as it looks like.
> protected void reduce(IntWritable key, Iterable<ClusterWritable> values, Context context) throws IOException,
> InterruptedException {
> Iterator<ClusterWritable> iter = values.iterator();
> ClusterWritable first = null;
> while (iter.hasNext()) {
> ClusterWritable cw = iter.next();
> if (first == null) {
> first = cw;
> } else {
> first.getValue().observe(cw.getValue());
> }
> }
> List<Cluster> models = new ArrayList<Cluster>();
> models.add(first.getValue());
> classifier = new ClusterClassifier(models, policy);
> classifier.close();
> context.write(key, first);
> }
> Apparently， the variable "first" will collect all output data of maps. Actually but, the value of "first" will change after the code "ClusterWritable cw = iter.next();", same with this new variable "cw"! I don't why but running result shows that the code runs looks like this:"ClusterWritable cw = first = iter.next();".
> is "cw" a reference a to "iter"?
> is "iter.next" just change the value of "iter" itself to the next?
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[jira] [Resolved] (MAHOUT-1083) CIReducer in kmeans doesn't work
well
Posted by "liutengfei (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/MAHOUT-1083?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
liutengfei resolved MAHOUT-1083.
--------------------------------
Resolution: Fixed
> CIReducer in kmeans doesn't work well
> -------------------------------------
>
> Key: MAHOUT-1083
> URL: https://issues.apache.org/jira/browse/MAHOUT-1083
> Project: Mahout
> Issue Type: Bug
> Environment: hadoop-2.0.0-alpha: pseudo cluster and single node cluster hadoop-1.0.3: pseudo cluster hadoop-0.20.2:pseudo cluster mahout: mahout-0.7 os: ubuntu 11.04 jdk: jdk1.6.0_27
> Reporter: liutengfei
> Attachments: MAHOUT-1083.patch
>
>
> the function "reduce" in mahout-0.7-kmeans-CIReducer.java doesn't work well as it looks like.
> protected void reduce(IntWritable key, Iterable<ClusterWritable> values, Context context) throws IOException,
> InterruptedException {
> Iterator<ClusterWritable> iter = values.iterator();
> ClusterWritable first = null;
> while (iter.hasNext()) {
> ClusterWritable cw = iter.next();
> if (first == null) {
> first = cw;
> } else {
> first.getValue().observe(cw.getValue());
> }
> }
> List<Cluster> models = new ArrayList<Cluster>();
> models.add(first.getValue());
> classifier = new ClusterClassifier(models, policy);
> classifier.close();
> context.write(key, first);
> }
> Apparently， the variable "first" will collect all output data of maps. Actually but, the value of "first" will change after the code "ClusterWritable cw = iter.next();", same with this new variable "cw"! I don't why but running result shows that the code runs looks like this:"ClusterWritable cw = first = iter.next();".
> is "cw" a reference a to "iter"?
> is "iter.next" just change the value of "iter" itself to the next?
--
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