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Posted to dev@hama.apache.org by "Samuel Guo (JIRA)" <ji...@apache.org> on 2008/12/09 13:36:44 UTC
[jira] Commented: (HAMA-130) Computing Block's range will miss some
cell during blocking.
[ https://issues.apache.org/jira/browse/HAMA-130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12654784#action_12654784 ]
Samuel Guo commented on HAMA-130:
---------------------------------
Also fix the bug from *SubMatrix*.
The bug from *SubMatrix* will fail the multiplication job during multiplying two matrices that are not square-matrices. Such as a(30 * 40) * b(40 * 30).
> Computing Block's range will miss some cell during blocking.
> ------------------------------------------------------------
>
> Key: HAMA-130
> URL: https://issues.apache.org/jira/browse/HAMA-130
> Project: Hama
> Issue Type: Bug
> Components: implementation
> Affects Versions: 0.1.0
> Reporter: Samuel Guo
> Assignee: Samuel Guo
> Priority: Critical
> Fix For: 0.1.0
>
> Attachments: HAMA-130.patch
>
>
> As the code below, in *BlockingMapper*, we compute the block's col range in a loop.
> if the block's size can integer-divide the matrix' column size, it is right.
> but if the block's size can not integer-divide the matrix' column size, some cells will be missed.
> for (int i = 0; i < mBlockNum; i++) {
> startColumn = i * mBlockColSize;
> endColumn = startColumn + mBlockColSize - 1;
> output.collect(new BlockID(blkRow, i), new VectorWritable(key.get(),
> dv.subVector(startColumn, endColumn)));
> }
> for examples:
> if the block num is 3, the matrix is 100 * 100. mBlockSize = 100 / 3 = 33.
> then <0 ~ 32>, <33 ~ 65>, <66 ~ 98> will be counted. At the same time we will lose column 99.
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