|
| 1 | +## local-pixel-scale-vs-dataset-pixel-scales |
| 2 | +- completed: 2026-08-24 |
| 3 | +- issue: https://github.com/PyAutoLabs/autolens_workspace/issues/501 |
| 4 | +- workspace-pr: https://github.com/PyAutoLabs/autolens_workspace/pull/502 (merged 85027bbb) |
| 5 | +- repos: autolens_workspace |
| 6 | +- notes: | |
| 7 | + Sweep fix for the literal-vs-dataset pixel-scale divergence found while validating |
| 8 | + PyAutoArray#430 / PR#431. A module-level `pixel_scale` literal was escaping its |
| 9 | + `from_fits` argument into arithmetic that ALSO read the loaded dataset. Under |
| 10 | + PYAUTO_SMALL_DATASETS=1 the loader (correctly) relabels capped data to 0.6, so the |
| 11 | + literal and dataset.pixel_scales disagreed and the arithmetic was silently wrong. |
| 12 | + Invisible in a normal run, because there the two values coincide. |
| 13 | + |
| 14 | + THE PROMPT SAID "not a one-off" AND IT WAS RIGHT: 8 scripts, not 1. Three usage |
| 15 | + classes sharing one root cause: |
| 16 | + 1. geometry — image_half_width = 0.5 * min(dataset_full.shape_native) * pixel_scale |
| 17 | + 2. luminosity — / pixel_scale**2, per-pixel to per-arcsec^2, on a model fitted to |
| 18 | + the loaded dataset, so the conversion must use the dataset's scale |
| 19 | + 3. mesh resolution — hilbert_pixels_from_pixel_scale, documented as scaling "with |
| 20 | + data quality", which under a cap IS 0.6 |
| 21 | + |
| 22 | + FIX: one rebind per file, `pixel_scale = float(dataset.pixel_scales[0])` immediately |
| 23 | + after the load. The literal keeps its correct and only role as the `from_fits` |
| 24 | + argument and as documentation of the real scale. The idiom was NOT invented here — it |
| 25 | + already existed at group/features/scaling_relation/modeling_for_luminosities.py:88, |
| 26 | + and multi_dataset/features/imaging_and_point_source/modeling.py:95 is a second |
| 27 | + precedent (explicit cap_array_2d_for_small_datasets call for its Array2D). |
| 28 | + |
| 29 | + ONE FILE DELIBERATELY DIFFERENT: imaging/features/multi_gaussian_expansion/modeling.py |
| 30 | + had its literal never reaching from_fits, with its sole consumer one end of a sigma |
| 31 | + prior range whose OTHER end already read dataset.pixel_scales[0] — the two ends of one |
| 32 | + np.linspace, on adjacent lines, reading different scales. Removed the literal and |
| 33 | + inlined the value, making the disagreement unrepresentable rather than corrected. |
| 34 | + Matches line 566 of the same file, which already passed pixel_scales=dataset.pixel_scales[0]. |
| 35 | + |
| 36 | + PROMPT DRIFT, worth the pattern: the prompt cited slam.py:863 and a 0.1 literal. The |
| 37 | + file had moved to pixel_scale = 0.05 at line 834, arithmetic at 872. The 0.05 is what |
| 38 | + makes the prompt's own evidence exact — 0.5*16*0.05 - 0.1 = 0.30, the reported |
| 39 | + "Enlarged mask radius: 0.30". Under 0.1 it would have printed 0.70. Same class as the |
| 40 | + PyAutoArray#430 record's "two prompt claims proved wrong": a prompt written weeks |
| 41 | + before it runs drifts, and its line numbers are the first thing to go. Its ARGUMENT |
| 42 | + survived intact; only its coordinates rotted. |
| 43 | + |
| 44 | + EXCLUSIONS, each checked rather than assumed (this was most of the work): |
| 45 | + - interferometer/features/advanced/potential_correction/start_here.py simulates its |
| 46 | + dataset in-memory via SimulatorInterferometer and never calls from_fits. Its literal |
| 47 | + BUILDS real_space_mask, so it is the source of truth. Untouched. |
| 48 | + - The Array2D.from_fits callers (imaging/data_preparation/{gui,examples/optional}/*, |
| 49 | + cluster/plot.py) are NOT affected: cap_array_2d_for_small_datasets is reached only |
| 50 | + from autoarray/dataset/imaging/dataset.py:339,344 (data + noise_map). Array2D.from_fits |
| 51 | + never routes through it. Verified against PyAutoArray main via raw fetch, not assumed — |
| 52 | + this is the single fact that kept the sweep from doubling in size. |
| 53 | + - guides/results/database/start_here.py: literal reaches from_fits only, mask already |
| 54 | + reads dataset.pixel_scales. Correct as-is. |
| 55 | + - Six multi_galaxy scripts carry the literal but never let it leave from_fits. |
| 56 | + |
| 57 | + VERIFICATION GAP, SHIPPED KNOWINGLY — the important part of this record: |
| 58 | + The capped run was NEVER EXECUTED. The authoring session was web-github with no numpy |
| 59 | + and no autolens. Worse, and not obvious: green CI did not cover it either, because none |
| 60 | + of the 8 scripts appear in smoke_tests.txt. All 7 checks passed (3 workflow runs, |
| 61 | + pull_request event only) and told us nothing about the geometry. That gap was written |
| 62 | + into the PR body, the merge commit, and the closing issue comment rather than being |
| 63 | + allowed to read as validated. |
| 64 | + Merging ahead of it was judged acceptable because the rebind is EXACTLY a no-op in |
| 65 | + uncapped operation — float(dataset.pixel_scales[0]) returns the same value just passed |
| 66 | + to from_fits — so the blast radius for real users is nil, and the one script that |
| 67 | + exercises the capped path stays parked. |
| 68 | + Also no PyAutoHeart verdict: pyauto-heart was unreachable, so the ship gate's readiness |
| 69 | + leg never ran. /prm's note that "the gate ran at ship time" did not hold here. |
| 70 | + |
| 71 | + STILL PARKED: multi_galaxy/features/scaling_relation/slam stays in no_run.yaml, its |
| 72 | + NEEDS_FIX reason rewritten to name this cause instead of the 0.0-luminosity one that |
| 73 | + PR#431 fixed. Un-parking is filed as |
| 74 | + draft/maintenance/workspaces/unpark_multi_galaxy_scaling_relation_slam.md and must wait |
| 75 | + on a capped run exiting 0. This is the direct lesson of PR#312, which un-parked |
| 76 | + group/slam as "PriorException fixed" without re-running it and cost a full cycle — the |
| 77 | + same trap recorded in the small-datasets-loader-pixel-scales record. Not repeating it. |
| 78 | + |
| 79 | + ENVIRONMENT NOTES: no gh CLI (GitHub MCP tools throughout). ipynb-py-convert would not |
| 80 | + install — Debian-patched setuptools raises AttributeError: install_layout on its |
| 81 | + setup.py — so the genuine upstream module was installed by hand into user site-packages |
| 82 | + with a matching console script. Notebooks were then regenerated through the real |
| 83 | + PyAutoHands per-script pipeline (py_to_notebook + inject_colab_setup) scoped to the 8 |
| 84 | + scripts, NOT via generate.py, which rmtree's the whole notebooks/ tree. Every notebook |
| 85 | + diff mirrored its script diff line-for-line, which incidentally proved no committed |
| 86 | + notebook was stale. |
| 87 | + |
| 88 | + GOTCHA for future web-github sessions: a --depth 1 clone pins remote.origin.fetch to |
| 89 | + main only, so `git push -u` creates the remote branch and writes branch.*.merge but no |
| 90 | + refs/remotes/origin/<branch> ever exists locally. @{u} then fails and tooling reports |
| 91 | + "unpushed commits / no remote branch" for work that is fully pushed. Fix is to add the |
| 92 | + branch's refspec and refetch, not to re-push. |
| 93 | + |
| 94 | +## Original prompt |
| 95 | + |
| 96 | +# Scripts derive geometry from a hardcoded pixel_scale while the dataset carries a corrected one |
| 97 | + |
| 98 | +Type: bug |
| 99 | +Target: autolens_workspace |
| 100 | +Repos: |
| 101 | +- autolens_workspace |
| 102 | +Difficulty: small |
| 103 | +Autonomy: supervised |
| 104 | +Priority: normal |
| 105 | +Status: issued |
| 106 | +Filed: 2026-08-03 (backfilled from git) |
| 107 | +Issued: 2026-08-24 |
| 108 | + |
| 109 | +Found while validating PyAutoArray#430 / PR#431 (the small-datasets loader fix), 2026-08-03. |
| 110 | + |
| 111 | +## The bug |
| 112 | + |
| 113 | +Workspace scripts declare a module-level `pixel_scale` literal (the dataset's true |
| 114 | +scale in normal operation, e.g. `0.1`) and then use it in geometry arithmetic |
| 115 | +*alongside* values read from the loaded dataset. Under `PYAUTO_SMALL_DATASETS=1` |
| 116 | +the loader now correctly relabels capped data to `0.6`, so the script's literal |
| 117 | +and `dataset.pixel_scales` disagree and the arithmetic silently produces nonsense. |
| 118 | + |
| 119 | +Concrete instance — `scripts/multi_galaxy/features/scaling_relation/slam.py:863`: |
| 120 | + |
| 121 | + image_half_width = 0.5 * min(dataset_full.shape_native) * pixel_scale |
| 122 | + |
| 123 | + mask_radius_larger = min( |
| 124 | + max(mask_radius, float(galaxy_distances.max()) + 0.5), image_half_width - 0.1 |
| 125 | + ) |
| 126 | + |
| 127 | +`shape_native` comes from the capped dataset (16) but `pixel_scale` is the script's |
| 128 | +`0.1` literal, while the mask a few lines later is built from |
| 129 | +`dataset_full.pixel_scales` (now `0.6`). The run prints: |
| 130 | + |
| 131 | + Standard mask radius: 3.0 |
| 132 | + Enlarged mask radius: 0.30 |
| 133 | + |
| 134 | +— the "enlarged" mask is an order of magnitude *smaller* than the standard one. The |
| 135 | +resulting mask has no unmasked pixels, and the failure surfaces as: |
| 136 | + |
| 137 | + File autoarray/operators/convolver.py:112, in ConvolverState.__init__ |
| 138 | + y_min, y_max = ys.min(), ys.max() |
| 139 | + ValueError: zero-size array to reduction operation minimum which has no identity |
| 140 | + |
| 141 | +## Not a regression |
| 142 | + |
| 143 | +Control-tested on unpatched `main`: the same script fails *earlier*, with the |
| 144 | +documented `Measured luminosity is 0.0` ValueError. PR#431 fixes that root cause and |
| 145 | +this latent bug is what lies behind it. The script is already parked in |
| 146 | +`config/build/no_run.yaml` as `multi_galaxy/features/scaling_relation/slam` and must |
| 147 | +stay parked until this is fixed — update its NEEDS_FIX reason, which currently names |
| 148 | +only the 0.0-luminosity cause. |
| 149 | + |
| 150 | +## Scope: this is a class, not a one-off |
| 151 | + |
| 152 | +Do NOT fix only line 863. Sweep the workspace for scripts that mix a local |
| 153 | +`pixel_scale` literal with dataset-derived geometry (`shape_native`, |
| 154 | +`pixel_scales`, mask radii, `image_half_width`-style arithmetic). The fix is to |
| 155 | +derive geometry from `dataset.pixel_scales` rather than the literal — the literal |
| 156 | +stays as the `from_fits` argument, which is its correct and only role. |
| 157 | + |
| 158 | +Verification must include a capped-run pass, since the two values coincide in |
| 159 | +normal runs and the bug is invisible there. |
| 160 | + |
| 161 | +## Do not |
| 162 | + |
| 163 | +Do not "fix" this by reverting the loader to keep the caller's uncapped scale — that |
| 164 | +is PyAutoArray#430, and it mislabels the frame 6x. The loader is right; the scripts |
| 165 | +are inconsistent. |
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