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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HAMA-13) Scalar and Matrix Multiplication
Date Wed, 20 Apr 2016 09:34:25 GMT

    [ https://issues.apache.org/jira/browse/HAMA-13?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15249554#comment-15249554

ASF GitHub Bot commented on HAMA-13:

Github user edwardyoon closed the pull request at:


> Scalar and Matrix Multiplication 
> ---------------------------------
>                 Key: HAMA-13
>                 URL: https://issues.apache.org/jira/browse/HAMA-13
>             Project: Hama
>          Issue Type: Improvement
>          Components: math
>            Reporter: Edward J. Yoon
>            Assignee: Edward J. Yoon
>         Attachments: HAMA-13.patch
> There are two types of multiplication for matrices: scalar multiplication and matrix
multiplication. Scalar multiplication is easy. You just take a number (called a "scalar")
and multiply it on every entry in the matrix. For example,
> For the following matrix A, find 2A :
> 2A = 2- {[a, b], [c, d]} = {[2- a, 2- b], [2- c, - d]}
> however, matrix multiplication is quite another story. We need to multiply the ROWS of
A by the COLUMNS of B. By this I mean that I first take the first row of A and the first column
of B, and we multiply the first entries, then the second entries, and then the third entries,
and then we add the three products. The sum is one entry in the product matrix AB.
> reference : http://carbon.cudenver.edu/csprojects/CSC5809S01/Simd/parmult.html

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