fix(flomni): reuse the same phase table for 360deg tomo instead of two

Supersedes the complementary even/odd-eighths tables from 900c810 with
a single shared phase_eighths table used in both 180 and 360 mode, so
subtomo N carries the same phase-tier role regardless of
tomo_angle_range. The complementary property of the low/high phase
sets now falls out as a consequence of the original table's structure
instead of needing a separately derived table.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

csaxs_bec/bec_ipython_client/plugins/flomni/flomni.py

@@ -2317,25 +2317,35 @@ class Flomni(
         the original scheme). In 360 mode each sub-tomogram instead
         covers only a 180-degree span - never the full circle - split by
         subtomo_number % 4 into a "low" half [0,180) (n%4 in (1,0)) and a
-        "high" half [180,360) (n%4 in (2,3)). Without this split, every
-        sub-tomogram's own 360-degree sweep would contain angle pairs
-        exactly 180 degrees apart - redundant tomographic information,
-        since a measurement 180 degrees from one already taken
-        contributes no new information.
+        "high" half [180,360) (n%4 in (2,3)), each sub-tomogram in the
+        high half literally its low-half counterpart's own 180-degree
+        scan, shifted by +180 (per subtomo_number, using the SAME
+        phase_eighths value as 180 mode - not a different phase table).
+        Without this split, every sub-tomogram's own 360-degree sweep
+        would contain angle pairs exactly 180 degrees apart - redundant
+        tomographic information, since a measurement 180 degrees from one
+        already taken contributes no new information.
 
-        Critically, the low half and high half use COMPLEMENTARY halves
-        of the original 8-way phase_eighths table (low: the even eighths
-        {0,2,4,6}; high: the odd eighths {1,3,5,7}), not the same phases
-        shifted by 180 - using the same phases would make every low-half
-        angle exactly 180 degrees from a high-half angle, reintroducing
-        the redundancy this scheme exists to remove. With complementary
-        phases, low and high each independently interlace their own half
-        at spacing step/4, but together - once the high half is folded
-        mod 180 - they reconstruct the full 8-way, step/8 grid with every
-        position hit EXACTLY once: the combined 360-degree angle set is
-        mod-180-identical to what an equivalent 180-degree scan would
-        produce, at the same total projection count, with zero redundant
-        measurements anywhere.
+        Reusing the same per-subtomo-number phase_eighths value in both
+        modes (rather than reassigning phases by acquisition order within
+        each half) is what makes subtomo N carry the same
+        interlacing/refinement role in both modes - e.g. subtomo 2 always
+        represents the phase_eighths[2] tier, whether that's within
+        [0,180) (180 mode) or shifted to [180,360) (360 mode, since
+        subtomo 2 % 4 == 2, a "high" sub-tomogram) - instead of an
+        unrelated phase suddenly appearing under the same subtomo number
+        depending on tomo_angle_range. Since the low half uses
+        subtomo_numbers {1,4,5,8} (phase_eighths values {0,6,1,7}) and the
+        high half uses {2,3,6,7} (phase_eighths values {4,2,5,3}), these
+        two phase sets are complementary (their union is all 8 eighths,
+        with no overlap) purely as a property of the original
+        phase_eighths table's structure - not something this branch has
+        to separately re-derive. Once the high half is folded mod 180,
+        low and high together reconstruct the full 8-way, step/8 grid
+        with every position hit EXACTLY once: the combined 360-degree
+        angle set is mod-180-identical to what an equivalent 180-degree
+        scan would produce, at the same total projection count, with zero
+        redundant measurements anywhere.
 
         Returns:
             angles (np.ndarray): the N angles (degrees) for this sub-tomogram.
@@ -2357,20 +2367,19 @@ class Flomni(
         N = int(180.0 / tomo_angle_stepsize)
         step = 180.0 / N
 
+        # Same phase_eighths table in both modes - see docstring above for
+        # why reusing it (rather than a separately-derived phase table for
+        # 360 mode) is what keeps subtomo N's role consistent between
+        # modes.
+        phase_eighths = {1: 0, 2: 4, 3: 2, 4: 6, 5: 1, 6: 5, 7: 3, 8: 7}
+        phase = step / 8.0 * phase_eighths[subtomo_number]
+
         if tomo_angle_range == 180:
             base = 0.0
-            phase_eighths = {1: 0, 2: 4, 3: 2, 4: 6, 5: 1, 6: 5, 7: 3, 8: 7}
-            phase = step / 8.0 * phase_eighths[subtomo_number]
             forward = bool(subtomo_number % 2)
         else:
-            # Low half (subtomos 1,4,5,8): even eighths. High half
-            # (subtomos 2,3,6,7): odd eighths. Complementary, not shared -
-            # see docstring above for why that's required to avoid
-            # redundant 180-degrees-apart measurements.
-            eighths = {1: 0, 4: 4, 5: 2, 8: 6, 2: 1, 3: 5, 6: 3, 7: 7}
             mod4 = subtomo_number % 4
             base = 0.0 if mod4 in (1, 0) else 180.0
-            phase = step / 8.0 * eighths[subtomo_number]
             forward = mod4 in (1, 2)
 
         if not explicit_start_angle:

tests/tests_bec_ipython_client/test_flomni_tomo_angles.py

@@ -94,6 +94,27 @@ def test_360_mode_mod_180_identical_to_180_mode(stepsize):
     assert set_folded == set180
 
 
+@pytest.mark.parametrize("stepsize", STEPSIZES)
+@pytest.mark.parametrize("n", range(1, 9))
+def test_360_mode_subtomo_keeps_same_phase_tier_as_180_mode(stepsize, n):
+    """Subtomo N must carry the same phase_eighths tier in 360 mode as in
+    180 mode - e.g. subtomo 2 always represents the phase_eighths[2] tier,
+    whether that's within [0,180) (180 mode) or shifted +180 into
+    [180,360) (360 mode). A previous implementation reassigned phases by
+    acquisition-order-within-half instead of reusing the per-subtomo-number
+    value, so e.g. the angle physically corresponding to subtomo 2's tier
+    in 180 mode ended up under subtomo 4 in 360 mode - confusing, and
+    breaks any expectation that "subtomo N" means the same thing across
+    modes."""
+    angles180, _, N, step = plan(n, 180, stepsize)
+    angles360, _, _, _ = plan(n, 360, stepsize)
+
+    base = 0.0 if n % 4 in (1, 0) else 180.0
+    offset180 = set(np.round(np.mod(angles180, step), 6))
+    offset360 = set(np.round(np.mod(angles360 - base, step), 6))
+    assert offset360 == offset180
+
+
 @pytest.mark.parametrize("tomo_angle_range", [180, 360])
 @pytest.mark.parametrize("stepsize", STEPSIZES)
 def test_resume_round_trip(tomo_angle_range, stepsize):