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From Sean Owen <sro...@gmail.com>
Subject Re: new to hadoop
Date Tue, 04 May 2010 16:10:05 GMT
I'll look into that. At first glance I'm not sure how it happens. This
part only executes if the vector has at least MAX_PREFS_CONSIDERED
nonzero elements. Each has a count of at least 1. So the sum must
eventually exceed that value. The dirty bit of this computation is
that it really needs to look at only counts that actually exist in the
map, otherwise it'll iterate through many counts that don't exist.
That should be few, but could be the source of an issue.

On Tue, May 4, 2010 at 4:23 PM, Tamas Jambor <jamborta@googlemail.com> wrote:
> thanks. I have identified the infinite loop. It is in
>
> org.apache.mahout.cf.taste.hadoop.item.UserVectorToCooccurrenceMapper.maybePruneUserVector(UserVectorToCooccurrenceMapper.java:88)
>
> where the resultingSizeAtCutoff variable remains zero, it does not increase.
>
> Tamas
>
> On 04/05/2010 15:35, Vimal Mathew wrote:
>>
>> "kill -QUIT" will cause the stack trace to be dumped to stderr (which
>> is usually a log file). You can also try
>>
>> jstack [java process ID]
>>
>> to read the stack trace directly.
>>
>> You can use  the "jps" command to list Java processes running on a system.
>>
>>
>>
>> On Mon, May 3, 2010 at 7:26 PM, Sean Owen<srowen@gmail.com>  wrote:
>>
>>>
>>> I think the infinite loop theory is good.
>>>
>>> As a crude way to debug, you can log on to a worker machine, locate
>>> the java process that may be stuck, and:
>>>
>>> kill -QUIT [java process ID]
>>>
>>> This just makes it dump its stack for each thread. Do that a few times
>>> and you may easily spot an infinite loop situation because it will
>>> just be in the same place over and over.
>>>
>>> http://java.sun.com/developer/technicalArticles/Programming/Stacktrace/
>>>
>>> On Tue, May 4, 2010 at 12:15 AM, Tamas Jambor<jamborta@googlemail.com>
>>>  wrote:
>>>
>>>>
>>>> It should be OK, because the hosts are in a local network, properly set
>>>> up
>>>> by the IT support.
>>>>
>>>> I guess the conf files should be OK too, because it runs the first two
>>>> jobs
>>>> without a problem only fails with the third. and it runs other hadoop
>>>> examples.
>>>>
>>>> I will look into how to debug a hadoop project, maybe I can trace down
>>>> the
>>>> problem that way.
>>>>
>>>>
>>>
>>>
>

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