Re: [swanmodel-users] not possible to compute, first iteration

[Stephen V. G. <sva...@fs...>]

Hi João,

Thanks for your response!  

When I run the non-stationary Hurricane Sandy test case I get this ... 

 Time of computation ->  20121001.000300      in sec:        180.
+time 20121001.000300   , step      1; iteration    1; sweep 1 grid   1
+time 20121001.000300   , step      1; iteration    1; sweep 2 grid   1
+time 20121001.000300   , step      1; iteration    1; sweep 3 grid   1
+time 20121001.000300   , step      1; iteration    1; sweep 4 grid   1
 accuracy OK in  35.47 % of wet grid points ( 98.00 % required)

 Time of computation ->  20121001.000600      in sec:        360.
+time 20121001.000600   , step      2; iteration    1; sweep 1 grid   1
+time 20121001.000600   , step      2; iteration    1; sweep 2 grid   1
+time 20121001.000600   , step      2; iteration    1; sweep 3 grid   1
+time 20121001.000600   , step      2; iteration    1; sweep 4 grid   1
 accuracy OK in  74.17 % of wet grid points ( 98.00 % required)


It looks like there is a single iteration at each time step followed by an accuracy calculation.
Something is happening here that is different from what’s going on in my model run.

Steve

> On Oct 29, 2019, at 7:37 PM, João Albuquerque <ja...@au...> wrote:
> 
> Hello Stephen,
> 
> Short answer: I think you don't have to worry about it.
> 
> Long answer:
> 
> When running on *stationary* mode Swan compares the accuracy improvement of the current computation and the computation of the previous iteration:
> 
>  iteration    2; sweep 1
>  iteration    2; sweep 2
>  iteration    2; sweep 3
>  iteration    2; sweep 4
>  accuracy OK in   1.62 % of wet grid points ( 99.50 % required)
> 
>  iteration    3; sweep 1
>  iteration    3; sweep 2
>  iteration    3; sweep 3
>  iteration    3; sweep 4
>  accuracy OK in   0.50 % of wet grid points ( 99.50 % required)
> 
> So, when you are running your first iteration, it is impossible to compute the accuracy since the previous computation does not exist:
>  iteration    1; sweep 1
>  iteration    1; sweep 2
>  iteration    1; sweep 3
>  iteration    1; sweep 4
>  not possible to compute, first iteration
> 
> When running on *non-stationary* mode, swan does not use the accuracy as a criterion to move to the next grid (in time) but I think it still computes several iterations before moving on. Probably this is what is happening at every new iteration and that's where the messages come from.
> 
> Best,
> João
> 
> On Wed, 30 Oct 2019 at 12:02, Stephen Van Gorder <sva...@fs...> wrote:
> Hi All,
> 
> I get the message "not possible to compute, first iteration” running in non-stationary mode.
> 
> Here is a clip from the PRINT file.
> 
> -----------------------------------------------------------------------------------------
>  Time of computation ->  20100414.000000      in sec:      86400.
> +time 20100414.000000   , step    480; iteration    1; sweep 1 grid   1
> +time 20100414.000000   , step    480; iteration    1; sweep 2 grid   1
> +time 20100414.000000   , step    480; iteration    1; sweep 3 grid   1
> +time 20100414.000000   , step    480; iteration    1; sweep 4 grid   1
>  not possible to compute, first iteration
> -----------------------------------------------------------------------------------------
> 
> Does anyone know what this means?
> 
> This is SWAN version 41.20 in COAWST version 3.4
> My SWAN input file is attached.
> 
> 
> 
> 
> Thanks,
> 
> Stephen Van Gorder  
> Senior Research Associate
> Earth, Ocean and Atmospheric Science
> Rogers Building, 421 OSB
> Florida State University
> Tallahassee, Fl 32306-4320
> 850-644-2447
> 
> 
> 
> 
> 
> 
> 
> _______________________________________________
> swanmodel-users mailing list
> swa...@li...
> https://lists.sourceforge.net/lists/listinfo/swanmodel-users
> 
> 
> -- 
> João Claudio Albuquerque
> PhD. Candidate, School of Environment, The University of Auckland,
> Level 4, Room 449, Science Centre, 23 Symonds Street, Auckland, NZ.
> +64 021 02365705
> _______________________________________________
> swanmodel-users mailing list
> swa...@li...
> https://urldefense.com/v3/__https://lists.sourceforge.net/lists/listinfo/swanmodel-users__;!5Xm4_O-4tfk!nWgBw2B784uyXd2DboqAOoxzOir7JBE1OhJ5wRu8Dp6Dj7Ib6j7CbuYdeDmJZVWE$