Hi Matt,

  Sorry, I should have been more clear. L and D are not lower triangular or anything, they are just matrices that are easy to invert in specific ways that are not compatible simultaneously.


all the best

--cjc

From: Matthew Knepley <knepley@gmail.com>
Sent: 30 April 2019 00:52:42
To: Cotter, Colin J
Cc: firedrake
Subject: Re: [firedrake] two splittings
 
On Mon, Apr 29, 2019 at 4:30 PM Cotter, Colin J <colin.cotter@imperial.ac.uk> wrote:

Dear Firedrakers,

  Greetings from Montreal. I'm thinking about a double splitting method to solve the system


(M + D + L)u = f, 


which as a preconditioner works out as


(M + D)^{-1}M(M + L)^{-1} r,


where r is a residual. 


In the absence of a better idea, I'll implement this through a Python preconditioner. But is there a smarter way to do this?


Isn;t this just SOR?

   Matt
 

all the best

--cjc

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