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-   -   Difference between GMRES and TDMA (http://www.cfd-online.com/Forums/main/12762-difference-between-gmres-tdma.html)

Mehdi January 3, 2007 15:27

Difference between GMRES and TDMA
 
Hi,

I am going to change my solver from TDMA to GMRES. Does anyone know which one is faster. I do not want to waiste my time by changing my solver.

Is there any big difference in CPU time if I use GMRES?

Regards,

raju January 4, 2007 11:56

Re: Difference between GMRES and TDMA
 
GMRES by itself is very inefficient (as far as my experience goes). It needs a good preconditioner. So you must have some knowledge about preconditioners.


Praveen. C January 4, 2007 12:56

Re: Difference between GMRES and TDMA
 
If you are using TMDA, I guess your matrix is triangular. TMDA is the best scheme in this case.

Luca Cavagna January 5, 2007 11:45

Re: Difference between GMRES and TDMA
 
Yes I agree with raju and praveen. If you have a tridiagonal matrix keep on using the TDMA which has been specifically developed. As raju said GMRES is not the solution to every problem! You need a good preconditioner to reduce the number of iteration and you may run out of memory is you have many degrees of freedom. Luca


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