Particles between actual non-rectangular grid and rectangular envelope of grid search forever before failing

[willirath]

Parcels version

< 4

Description

(This is a bug in older parcels versions but as we're still running some v3 for production, I'm finding myself patching index search .h files. So I still want to report here.)

A colleague (@elenagebauer) is running Parcels experiments in nested fields on these grids:

(from https://doi.org/10.5194/gmd-13-4959-2020) and finds particles from just outside the western boundary of the finest nested grid searching all the way up to int maxIterSearch = 1e6 until they finally realize they're supposed look in the next coarser grid.

This is due to the fact that

Parcels/parcels/include/index_search.h

Lines 351 to 358 in 1ce5908

	if (zonal_periodic == 0){
	if ((x < xy_minmax[0]) || (x > xy_minmax[1])){
	if (xgrid[0][0] < xgrid[0][xdim-1]) {return ERROROUTOFBOUNDS;}
	else if (x < xgrid[0][0] && x > xgrid[0][xdim-1]) {return ERROROUTOFBOUNDS;}
	}
	}
	if ((y < xy_minmax[2]) || (y > xy_minmax[3]))
	return ERROROUTOFBOUNDS;

only checks if a particle is out of the rectanugular envelope of the grid (as defined by xy_minmax) and then goes on to look for its grid point forever.

A possible fix is to really check if a particle is outside the tight envelope of the grid before searching. @elenagebauer and I are currently working on a point-in-polygon check for failing fast on non-global grids. We'll feed this back once we got it right.