Re: implement a SOR like routine efficiently

[Ganesh Bikshandi]

Thanks for the solutions. But I am not sure if they will work. I will
try them, anyways.

Ganesh 


On Tue, 16 Nov 2004 10:40:17 -0500 (EST), Przemek Klosowski
<address@hidden> wrote:
> 
> 
> 
>    I need to implement the following loop efficiently:
> 
>    for i = 2:n-1
>      for j = 2:n-1
>          a(i,j) = a(i-1,j) + a(i+1,j) + a(i,j+1) + a(i,j-1)
>       end
>    end
> 
>    The loop is not vectorizable, as it has a carried dependence. If I run
>    this loop as it is, it is very slow ( in my program n is  256 and
> 
> Well, as written, the loop is not vectorizable; but the expression is
> suspiciously close to an 'averaging' kernel. I just wanted you to
> confirm that a convolution of a and [0 1 0; 1 0 1; 0 1 0] would not be
> an acceptable solution:
> 
>         a(2:n-1,2:n-1) = conv2(a, [0 1 0; 1 0 1; 0 1 0],'valid');
> 
>



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