fix: FixedCell setter atomically adds agent before updating reference (fixes #3411)#3415
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fix: FixedCell setter atomically adds agent before updating reference (fixes #3411)#3415
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quaquel
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Mar 2, 2026
mesa/discrete_space/cell_agent.py
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| self._mesa_cell = cell | ||
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| def cell(self, cell: Cell | None) -> None: | ||
| if self._mesa_cell is not None and cell is not self._mesa_cell: |
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This still allows reassigning the same cell. I would just block any assignment after self._mesa_cell is no longer None.
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simplified it just blocks any assignment once _mesa_cell is set
quaquel
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Mar 2, 2026
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There is an indentation error. Can you fix that? As a general rule, I suggest running all tests locally before committing changes. |
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Performance benchmarks:
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Sorry about that Fixed the indentation and ran tests locally before pushing this time |
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@quaquel all done |
EwoutH
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EwoutH
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Problem
FixedAgent kept a dangling reference to a cell that rejected it due to capacity.
After a failed cell.add_agent(), agent.cell was set but the cell had no record of the agent.
Fix
Swap the order in FixedCell.cell.setter — call cell.add_agent(self) FIRST,
then update self._mesa_cell only if it succeeds. This is the same atomic
pattern already used in HasCell (PR #3374).
Fixes #3411