[Bug]: Cell‐centered slice at PBY=0.55 snaps to 0.60000002 instead of 0.55

[ManuelOsburg]

What happened?

Description:
When requesting a cell‐centered slice at PBY=0.55 on a uniform 0.1 m grid, fdsreader returns y = [0.60000002] instead of 0.55. Even if ignore_cell_centered=True is passed to get_coordinates(), the result remains 0.60000002. The cell centers on a 0.1 m grid are at

0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95

so a request for PBY=0.55 with CELL_CENTERED=T should locate that exact cell center at 0.55 m.

Steps to reproduce

Reproduction:

1. Use a 1 m domain with 0.1 m grid spacing in y (nodal y: 0.0, 0.1, …, 1.0).
2. In FDS input:

&SLCF PBY=0.50, QUANTITY='TEMPERATURE' /
&SLCF PBY=0.55, CELL_CENTERED=T, QUANTITY='TEMPERATURE' /

3. In Python:

import fdsreader as fds
import os

sim = fds.Simulation(os.getcwd())

for slc in sim.slices:
    print(slc.cell_centered, slc.get_coordinates(ignore_cell_centered=False)["y"])

Output:

False  [0.5]
True   [0.60000002]

4. Now call with ignore_cell_centered=True:

for slc in sim.slices:
    print(slc.cell_centered, slc.get_coordinates(ignore_cell_centered=True)["y"])

Output:

False  [0.5]
True   [0.60000002]

Expected Behavior:

• For PBY=0.50, CELL_CENTERED=False → y = [0.50].

• For PBY=0.55, CELL_CENTERED=True → y = [0.55], because there is a cell center exactly at 0.55 m.

• If ignore_cell_centered=True, then the slice should be treated as nodal (so nodal values exist at 0.0, 0.1, …, 1.0), but when CELL_CENTERED=True is present in the slice definition, the coordinates for that slice are still drawn from a pre‐shifted cell‐center array. In either case, a request for PBY=0.55 should not return 0.60000002.

Actual Behavior:

• With ignore_cell_centered=False and CELL_CENTERED=False, y = [0.5].

• With ignore_cell_centered=False and CELL_CENTERED=True, y = [0.60000002].

• With ignore_cell_centered=True and CELL_CENTERED=True, y = [0.60000002].

In all cases where CELL_CENTERED=True and PBY=0.55, fdsreader returns 0.60000002 instead of 0.55.

test.zip

FDS version used

FDS-6.10.1-0-g12efa16-release

fdsreader version used

fdsreader, version 1.11.6