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MathGroup Archive 2007

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Re: Complexity explosion in linear solve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg80288] Re: Complexity explosion in linear solve
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Thu, 16 Aug 2007 07:22:18 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <200708141107.HAA09644@smc.vnet.net><f9ueas$b9n$1@smc.vnet.net> <fa12qe$mn6$1@smc.vnet.net>

carlos at colorado.edu wrote:

>> Try Method->"OneStepRowReduction" (without quotes, if in versions < 6) and
--------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> see if that helps.

<snip>

>> Daniel Lichtblau
>> Wolfram Research
> 
> When I tried that option under version 5.2 for Mac OS X,
> the expression returns unevaluated.  I could not find documentation
> for it; what does it do?

<snip>

Have you tried without quotes? Without quotes surrounding the value for 
the option, the following works fine on my system.

In[1]:=
$Version
mat = {{1, 2, 3}, {1, 3, 4}};
b = {5, 8};
x = LinearSolve[mat, b, Method -> OneStepRowReduction]

Out[1]=
5.2 for Microsoft Windows (June 20, 2005)

Out[4]=
{-1, 3, 0}

(More information can be found in Michael Trott's _The Mathematica 
GuideBook for Programming_, p 826: "Method is an option for the commands 
LinearSolve, Inverse, RowReduce (to be treated soon), and NullSpace. It 
defines the internal algorithm to be used in the computation. Default: 
Automatic. Admissible: DivisionFreeRowReduction or CofactorExpansion or 
OneStepRowReduction.")

HTH
-- 
Jean-Marc


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