Regression test support for i.eb.hsebal01

GRASS GRASS developer
1

Hi Everyone,

I was recently working on writing regression test suite for the i.eb.hsebal01 module, and I have encountered persistent failures due to Delta T Convergence failed errors, even when providing seemingly valid and diverse synthetic input maps.

The purpose of this test is to simulate minimal but physically consistent input conditions that can:

  • trigger both manual and automatic pixel detection modes,
  • provide stable heat flux results for future validation,
  • and help ensure stability in CI environments.

Inputs Used

I am working in a small test region (10x10, LL projection). Inputs include:

  • netradiation: higher over vegetated pixels
  • soilheatflux: computed as 30% of Rn
  • temperaturemeansealevel: cooler in wet zones, hotter in dry
  • vapourpressureactual: higher for wet zones
  • aerodynresistance: inversely correlated with NDVI
  • frictionvelocitystar: ~0.25 (nominal)

Example NDVI generation:

r.mapcalc expression="ndvi = if(row()==5 && col()==5, 0.8, if(row()==9 && col()==9, 0.1, 0.5 + 0.05 * rand(0,1)))"

I have explicitly declared (5,5) as wet and (9,9) as dry pixels for the manual mode.

Problem

Despite a stable region and reasonable gradients between wet and dry zones, the module still fails with:

ERROR: Delta T Convergence failed, exiting prematurely, please check output

This happens both with -a (automatic detection) and with manually specified wet/dry coordinates.

What I have Tried

  • Aligning g.region to raster extents (e.g., g.region raster=ndvi)
  • Using float values vs integer
  • Adjusting synthetic values to stay within realistic SEBAL bounds
  • Setting row_wet_pixel, column_wet_pixel manually
  • Testing against both stable and dev builds of GRASS 8.4

If anyone has:

  • suggestions on stabilizing Delta T convergence with synthetic data,
  • or knowledge of thresholds/tolerances in the internal logic,

I would greatly appreciate any guidance. Ultimately, I would like to contribute this as a full regression test under imagery/i.eb.hsebal01/testsuite.

Thanks in advance!

2

Unless the author @ychemin wants to comment, I suggest to move on a different tool.