Fix float32 truncation in balanced_allocation iteration loop (#1203)#1205
Merged
brendancol merged 1 commit intomasterfrom Apr 15, 2026
Merged
Fix float32 truncation in balanced_allocation iteration loop (#1203)#1205brendancol merged 1 commit intomasterfrom
brendancol merged 1 commit intomasterfrom
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_allocate_biased and _allocate_from_costs cast the allocation array to float32 internally. The balancing loop then compared these float32 values against float64 source IDs. For non-integer IDs (e.g. 0.1, 0.3) the float64->float32->float64 round-trip produces a different value, so alloc == sid never matched, weights were all zero, and the loop exited on the first iteration without balancing. Fix: keep the allocation array as float64 through the iteration loop. The final cast to float32 happens at the return statement.
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Closes #1203.
Summary
_allocate_biasedand_allocate_from_costscast the allocation array tofloat32internally. The balancing loop then compared thesefloat32valuesagainst
float64source IDs. For non-integer source IDs (e.g. 0.1, 0.3),float64 -> float32 -> float64produces a different value, soalloc == sidnever matched and the loop exited on the first iteration without balancing.
float64for the allocation array. The finalcast to
float32already happens at the return statement.the fix.
Test plan
test_non_integer_source_ids-- three sources with IDs 0.1, 0.3, 0.7on a 12x12 grid. Verifies each territory gets at least 20% of cells.
test_balanced_allocation.pytests still pass.