Remove Sample Rate Rounding#1073
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Pull request overview
This PR updates how sample_rate is computed for the households table by removing the previous rounding to 3 decimal places, preserving full precision to avoid zero sample rates for small household samples (which can cause 1 / sample_rate to overflow in downstream trip matrix logic).
Changes:
- Remove rounding from
sample_ratecalculation inactivitysim/abm/tables/households.py. - Add a new unit test validating
sample_ratecalculation for small sampling rates.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| activitysim/abm/tables/households.py | Computes sample_rate using full-precision division instead of rounding. |
| activitysim/abm/test/test_misc/test_sample_rate.py | Adds a regression/unit test covering small sample_rate values. |
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| if households_sample_size == 0: | ||
| sample_rate = 1 | ||
| else: | ||
| # TODO: do not round, keep full precision to avoid creating 0 sample_rate for small samples | ||
| # Existing CI tests will fail when performing bitwise comparisons with the unrounded sample_rate | ||
| # We should update the CI tests | ||
| sample_rate = round(households_sample_size / tot_households, 3) | ||
| sample_rate = households_sample_size / tot_households | ||
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| df["sample_rate"] = sample_rate |
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| "household_id": range(1, 100001), | ||
| "home_zone_id": [1, 2] * 50000, |
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| assert ( | ||
| sample_rate == 0.00002 |
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This pull request makes a small but important change to the calculation of
sample_ratein thehouseholdstable logic. Instead of roundingsample_rateto three decimal places, which can result in a value of 0 for small sample sizes, the code now preserves the full precision of the division. This ensures meaningful values (not NaN or Inf) in trip matrices that use the inverse of the sample rate in their calculations.Code changes: a simple change in the
households.py.Test updates:
sample_ratetarget values to full precision in the failed SANDAG tests. Update Sample Rate in Regress Targets sandag-abm3-example#42sample_ratecalculation.