From: "pypypy567 (py _)" <redmine@...>
Date: 2012-12-18T01:15:20+09:00
Subject: [ruby-core:50946] [ruby-trunk - Bug #7582][Open] a mistake in Matrix#lup RDoc


Issue #7582 has been reported by pypypy567 (py _).

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Bug #7582: a mistake in Matrix#lup RDoc
https://bugs.ruby-lang.org/issues/7582

Author: pypypy567 (py _)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 2.0.0dev (2012-11-01) [i386-mswin32_100]


http://bugs.ruby-lang.org/projects/ruby-trunk/repository/revisions/38300/entry/lib/matrix.rb#L1203
>   #   l * u == a * p      # => true
http://bugs.ruby-lang.org/projects/ruby-trunk/repository/revisions/38300/entry/lib/matrix/lup_decomposition.rb#L7
>   # and a m-by-m permutation matrix P so that L*U = P*A.


irb(main):001:0> require 'matrix'
=> true
irb(main):002:0> a = Matrix[[1, 2], [3, 4]]
=> Matrix[[1, 2], [3, 4]]
irb(main):003:0> l, u, p = a.lup
=> #<Matrix::LUPDecomposition:0xf813a8 @lu=[[3, 4], [(1/3), (2/3)]], @row_size=2, @col_size=2, @pivots=[1, 0], @pivot_sign=-1>
irb(main):004:0>  l * u == a * p
=> false
irb(main):005:0>  l * u == p * a
=> true



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