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https://issues.apache.org/jira/browse/MAHOUT-122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12718771#action_12718771
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Deneche A. Hakim commented on MAHOUT-122:
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I was wrong about the memory usage of the current implementation, even that
each node has its own Data object, all the Data object still share the same
Instance objects which all the actual data.
I did some profiling and I found that "InformationGain.computeSplit()" method
takes nearly 98.5% of total time, this is responsible for computing the
Information Gain for the current split. So if we want later to optimize this
implementation we'll have to use a better algorithm to compute the Information
Gain, the one that I'm aware of and which is available in the Weka source code,
computes
the sorting indices for the data with each attribute.
I also did some memory usage profiling using a Runnable that samples every 50ms
a rough estimation of memory usage using (Runtime.getTotalMemory() -
Runtime.getFreeMemory()). I used the KDD dataset (> 700 Mb of data), I then
created different datasets using subsets of different size (1%, 10%, 25%, 50%).
Here are the results :
KDD has 41 attributes (stored as "double")
KDD 1% has 49402 instances
KDD 10% has 494021 instances
KDD 25% has 1224607 instances
KDD 1% contains
Dataset Nb Trees MUALD(*) Max Used Memory Nb Nodes
Max Tree Depth
KDD 1% 1 35.414.504 b 38.069.640 b 120
10
KDD 1% 10 35.144.096 b 45.669.904 b 126 (mean)
11 (mean)
KDD 10% 1 201.697.512 b 226.653.392 b 712
22
KDD 25% 1 521.515.136 b 569.795.152 b 930
26
(*) Memory used right after loading the Data
I should run more tests using KDD 50% and KDD 100%, and also building more
trees to see how the memory usage behaves. But because the current
implementation is very slow, it may take some time
> Random Forests Reference Implementation
> ---------------------------------------
>
> Key: MAHOUT-122
> URL: https://issues.apache.org/jira/browse/MAHOUT-122
> Project: Mahout
> Issue Type: Task
> Components: Classification
> Affects Versions: 0.2
> Reporter: Deneche A. Hakim
> Attachments: 2w_patch.diff, RF reference.patch
>
> Original Estimate: 25h
> Remaining Estimate: 25h
>
> This is the first step of my GSOC project. Implement a simple, easy to
> understand, reference implementation of Random Forests (Building and
> Classification). The only requirement here is that "it works"
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