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

[João A. <ja...@au...>]

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