fix(core): Min/Max, NaN and signed zero follow the math, not the old fold (improvise-bw4p.20)
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze
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Claude (dbsp-backend)
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Edward Langley
Edward Langley
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@@ -314,8 +314,8 @@ because they change nothing observable (below); every other is named by at least
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`group::tests::an_emptied_group_is_absent_and_keeps_no_entries`,
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`incremental_matches_eager_on_the_shipped_documents`, `incremental_equals_eager_over_random_edit_sequences`;
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- a group never counts its numbers: `a_group_read_comes_from_a_maintained_group`,
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`group::tests::min_and_max_skip_nan_and_are_infinite_over_nothing_else` and eight differentials;
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- `Max` takes the first key: `group::tests::min_and_max_skip_nan_and_are_infinite_over_nothing_else`,
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`group::tests::min_and_max_skip_nan_and_are_nan_over_nothing_else` and eight differentials;
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- `Max` takes the first key: `group::tests::min_and_max_skip_nan_and_are_nan_over_nothing_else`,
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`an_overwrite_costs_two_updates_per_shape_whatever_the_table_size` and five differentials;
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- `Count` counts one: `a_collapsed_group_reads_one_group_per_member_it_covers`, `group::tests::*`;
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- unanimity ignores disagreement: `group::tests::text_is_unanimous_or_mixed_across_groups`,
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@@ -437,7 +437,7 @@ A multiset that ignores a negative weight keeps the minimum it should have lost.
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After the last retraction the group reads as absent and its map holds no zero-weight entry.
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### group::tests::min_and_max_skip_nan_and_are_infinite_over_nothing_else
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### group::tests::min_and_max_skip_nan_and_are_nan_over_nothing_else
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NaN is skipped by `Min` and `Max`, a group of only NaN gives `+inf` and `-inf` and still counts.
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@@ -472,7 +472,7 @@ What each fault was and the test that names it:
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`a_formula_that_keeps_moving_for_sixteen_passes_is_circular`,
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`dependency_order_and_the_plain_passes_leave_the_same_cache`;
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- dependencies after dependents: `dependency_order_and_the_plain_passes_leave_the_same_cache` and five more;
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- NaN is not marked circular: `a_formula_cell_holding_nan_is_circular_and_the_cells_that_read_it_keep_the_nan_they_read`;
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- NaN is not marked circular: `a_formula_cell_holding_nan_is_nan_and_not_circular`;
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- fifteen passes / seventeen passes: `a_chain_added_last_link_first_is_circular_exactly_where_eager_says`;
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- the passes end without marking the cells still moving, or begin from the old cache:
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`a_chain_added_last_link_first_is_circular_exactly_where_eager_says`,
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@@ -557,7 +557,7 @@ the whole recompute.
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`IF(Revenue > 1000, B, Revenue)`: at the stem of a big product it reads the cache of the stem of B,
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which is evaluated after it. Fails when such a formula set is not wide.
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### a_formula_cell_holding_nan_is_circular_and_the_cells_that_read_it_keep_the_nan_they_read
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### a_formula_cell_holding_nan_is_nan_and_not_circular
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NaN is not equal to itself, so eager's passes never see it settle. Fails when the ordered path leaves it.
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@@ -643,7 +643,7 @@ runs because its two heaviest tests shared it. The tests are unchanged.
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East plus the maximum of West), the first version kept 14. Fails when a new aggregation dirties only
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the stems of formulas that name the measure, and when `Stems::carrying` ignores the measure.
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### a_new_aggregation_reaches_a_product_targeted_filtered_sum
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### a_new_aggregation_reaches_a_filtered_sum_on_the_fallback_path
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The reviewer's second repro, a Product-targeted `SUM(F0 WHERE Region = East)`. It already agreed on this
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fixture and stays as the second shape of the same hazard.
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@@ -766,3 +766,22 @@ average of a rounded sum.
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Infinities and NaN read as `ExactSum::value` does, and a zero keeps its sign.
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## Eager's math, fixed (follow-up to steps 4 to 6)
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Ruling (user, 2026-10-10): do not reproduce math bugs found in Eager; fix Eager. Eight faults were
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injected (six in the table below, two more in the groups' NaN handling); `nan-never-settles` survived the
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first pass because NaN produced by one evaluation always has the same bits, and is closed by a unit test of
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`settled`. Each fix has a regression test named after the bug:
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- `model::types::eager_math_tests::min_and_max_of_both_zeros_do_not_depend_on_their_order` and
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`with_both_zeros_min_is_negative_and_max_is_positive_whatever_the_order`: a naive `f64::min` fold
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passes on ARM and fails on other platforms, so the rival is a fold that keeps the first of two zeros;
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- `model::types::eager_math_tests::min_and_max_over_only_nan_are_nan_not_infinite`,
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`min_and_max_over_only_nan_are_nan_in_both_backends`, `group::tests::min_and_max_skip_nan_and_are_nan_over_nothing_else`;
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- `model::types::eager_math_tests::a_formula_that_settles_on_nan_is_nan_and_not_circular`,
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`a_formula_cell_holding_nan_is_nan_and_not_circular`, `settled_treats_every_nan_as_one_value_and_the_zeros_as_two`;
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- `model::types::eager_math_tests::a_zero_that_changes_sign_between_passes_settles_on_the_new_sign` and
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`ordered_evaluation_keeps_the_zero_eager_settles_on` (now with the sign settled by bits, no fallback);
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- `model::types::eager_math_tests::a_formula_that_never_settles_is_still_circular`: the guard that a real
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oscillation is still `circular`.
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The random and differential suites compare numbers by bits and their pools hold both zeros again.
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