Error : The following floating-point exceptions are signalling: IEEE_UNDERFLOW_FLAG

[Natalie Svolos]

SWAT+ Issue Report Template

1. Primary Issue Location

• Component: QSWAT+/SWAT+
• Area of impact: Visualization step not occurring

2. Software Versions

• GIS Interface: QGIS 3.44 LTR  SWAT+ Editor: 4.0.0 SWAT+ Revision:

3. Project Characteristics

• Watershed Details: Using the Robit example data
• Modeling Aim: 

4. Description of Issue

• The Problem: I am trying to run the Robit example data, it seems the simulation is working but the visualization is not. I get this error: Note: The following floating-point exceptions are signalling: IEEE_UNDERFLOW_FLAG. It seems like all of the files exist but step 4 in the QSWAT+ interface doesn't appear. 
• Step to Reproduce: Running the robit QSWAT+ example data as described in the manual

5. Supporting Data (Optional)

• Link to TxtInOut folder: https://drive.google.com/drive/folders/1zHnFzI00U1TC9g45i8PLO6uI9lAApL70?usp=sharing

[Chris George]

Hi Natalie,

I have tried running your example with the latest SWAT+ executable
(version 62) and there are no errors. It is not clear from your message
what application is producing the exception.

Visualization is only available if the SWAT+ executable finishes
successfully and you ticked the "Analyze output for visualization" box
in the SWAT+ editor. Specifically, a swatplus_output.sqlite file must
exist in the project's Scenarios/Deafault/Results folder.

Chris

On 8/4/2026 9:54 PM, Natalie Svolos wrote:
> SWAT+ Issue Report Template 1. Primary Issue Location Component: 
>  QSWAT+/SWAT+ Area of impact: Visualization step not occurring 2.
> Software Versions GIS Interface:  QGIS 3. 44 LTR  SWAT+ Editor:  4. 0. 
> 0 SWAT+ Revision: 3. Project Characteristics

> ZjQcmQRYFpfptBannerStart
> This Message Is From an External Sender
> This message came from outside your organization.
> ZjQcmQRYFpfptBannerEnd
>
> *SWAT+ Issue Report Template*
>
> *1. Primary Issue Location*
>
> * *Component:* QSWAT+/SWAT+
> * *Area of impact: *Visualization step not occurring
>
> *2. Software Versions*
>
> * *GIS Interface:* QGIS 3.44 LTR *SWAT+ Editor:* 4.0.0 *SWAT+ Revision:*
>
> *3. Project Characteristics*
>
> * *Watershed Details:* Using the Robit example data
> * *Modeling Aim:*
>
> *4. Description of Issue*
>
> * *The Problem:* I am trying to run the Robit example data, it seems

> the simulation is working but the visualization is not. I get this
> error: Note: The following floating-point exceptions are signalling:
> IEEE_UNDERFLOW_FLAG. It seems like all of the files exist but step 4
> in the QSWAT+ interface doesn't appear.

> * *Step to Reproduce:* Running the robit QSWAT+ example data as
> described in the manual
>
> *5. Supporting Data (Optional)*
>
> * *Link to TxtInOut folder:*https://drive.google.com/drive/
> folders/1zHnFzI00U1TC9g45i8PLO6uI9lAApL70?usp=sharing
>
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[Jaclyn Tech]

Hi Natalie, 

It ran fine for me too, and I'm not getting any IEEE_UNDERFLOW_FLAG error -- which indicates a Fortran problem, which would prohibit the output from being processed by the editor.

Can you confirm a few things?

1. Check your SWAT+ Editor model executable folder as shown in the screenshot? It should just have the 6 files shown.

2. Share a screenshot of the actual window after you run. Is there anymore text or information there?

3. Zip and share your full project folder in case there is something we're missing in there that could be causing this.

Thanks,

Jaclyn

[Jaclyn Tech]

Oh a Mac! That explains it. I will forward to our developer who compiled for Mac. It could either be a problem in the executable or a weird circumstance we have to work around.

Thanks,

Jaclyn

[Jaclyn Tech]

Hello Natalie,

This issue has been resolved. Please run the install script again to update the SWAT+ Editor with the latest fix.

The problem was caused by compiler differences between gfortran (Mac) and Intel (other platforms). Gfortran was generating a false error code despite successful model execution. The editor now handles this correctly by monitoring additional console output.

Let us know if you encounter any other problems.