# \[Archive\] Cholesky DECOMPOSITION

**URL:** <https://forum.spis.org/t/archive-cholesky-decomposition/418>\
**Category:** SPIS\
**Created:** [4 May 2005 16:08 UTC](https://forum.spis.org/t/archive-cholesky-decomposition/418 "2005-05-04T16:08:00Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![system](https://forum.spis.org/uploads/default/original/1X/887f7e402a70666bad1816db2c64fefd698b4b0f.png) [@system](https://forum.spis.org/u/system)\
**Post date:** [4 May 2005 16:08 UTC](https://forum.spis.org/t/archive-cholesky-decomposition/418/1 "2005-05-04T16:08:00Z")

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Message by **julien** :  
Initially posted the Fri Nov 26, 2004 3:34 pm by markelov, forwarded by juju.  
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Howdy,  
when I slightly changed a size of a geometry, SPIS solver complains each time step  
WARNING : Error in Cholesky DECOMPOSITION of preconditionnig ) = 5413  
This is a warning or error? Can I neglect it?  
Thank you. Regards, Gennady

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**Author:** ![system](https://forum.spis.org/uploads/default/original/1X/887f7e402a70666bad1816db2c64fefd698b4b0f.png) [@system](https://forum.spis.org/u/system)\
**Post date:** [4 May 2005 16:08 UTC](https://forum.spis.org/t/archive-cholesky-decomposition/418/2 "2005-05-04T16:08:00Z")

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Message by **julien** :  
Initially posted Mon Dec 06, 2004 8:41 am by roussel, forwarded by juju.  
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You can neglect it if it does not show up again (usually it happens only the first time because of a bad definition of convergence criterion at first solver call, when it starts from 0 values) JF  
Jean-François Roussel

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**Author:** ![system](https://forum.spis.org/uploads/default/original/1X/887f7e402a70666bad1816db2c64fefd698b4b0f.png) [@system](https://forum.spis.org/u/system)\
**Post date:** [4 May 2005 16:08 UTC](https://forum.spis.org/t/archive-cholesky-decomposition/418/3 "2005-05-04T16:08:00Z")

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Message by **julien** :  
Initially posted Thu Dec 09, 2004 2:57 pm by markelov, forwarded by juju.  
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Thank you for the reply but I have it \_each time step\_  
Regards, Gennady

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**Author:** ![system](https://forum.spis.org/uploads/default/original/1X/887f7e402a70666bad1816db2c64fefd698b4b0f.png) [@system](https://forum.spis.org/u/system)\
**Post date:** [19 April 2010 15:24 UTC](https://forum.spis.org/t/archive-cholesky-decomposition/418/4 "2010-04-19T15:24:00Z")

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Message by **Nuno Loureiro** :  
Hello,  
I am having the same problem (at each time step) and I can’t understand why this happens. Can anyone explain what is the cause of it?  
Thanks  
Nuno

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**Author:** ![system](https://forum.spis.org/uploads/default/original/1X/887f7e402a70666bad1816db2c64fefd698b4b0f.png) [@system](https://forum.spis.org/u/system)\
**Post date:** [19 April 2010 15:40 UTC](https://forum.spis.org/t/archive-cholesky-decomposition/418/5 "2010-04-19T15:40:00Z")

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Message by **Jean-Francois Roussel** :  
Preconditioning is used to improve the convergence speed of Poisson solver.  
In some situations (bad quality mesh e.g.) the Cholesky matrix decomposition used for that, fails.  
You don’t have to worry too much if that happens, the only consequence is on the computation time.  
Jean-François

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**Author:** ![system](https://forum.spis.org/uploads/default/original/1X/887f7e402a70666bad1816db2c64fefd698b4b0f.png) [@system](https://forum.spis.org/u/system)\
**Post date:** [10 July 2020 11:26 UTC](https://forum.spis.org/t/archive-cholesky-decomposition/418/6 "2020-07-10T11:26:22Z")

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Closed on 10 July 2020 11:26 UTC