leonarski_fandClaude Opus 5.5
082f77eaa8
The ladder stepped the beam centre a pixel at a time after a rotation first pass that indexed fewer than half the validation frames. A battery with it switched off changed no output, so it goes: the option, its usage text, ProcessConfig::beam_center_search_pxl, the once-per-run flag that kept probes, walks and later passes from re-running it, and the docs. The background centre measurement, the beam-centre check that indexes at the measured centre, the merge-judged arms and the post-refinement of the centre are unchanged. rugnux now rejects --beam-center-search as an unknown option. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01SVmAWnzCmRKAXVUCdc4iNi
75 lines
5.1 KiB
Markdown
75 lines
5.1 KiB
Markdown
# What Rugnux does
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The map of a run, in the order it happens — one paragraph per stage, each linking into the
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[data-analysis reference](CPU_DATA_ANALYSIS.md) where the algorithm lives. The walk-through is a
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rotation run with the defaults; stills differences are at the end.
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**Open the dataset.** The geometry, wavelength and goniometer come from the file
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([What Rugnux reads](RUGNUX_FORMATS.md)). A goniometer axis makes it a rotation run, none makes it
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serial stills — nothing is asked of the user.
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**Pre-scan.** A projection of frames spread over the sweep (60 by default) finds the beam-stop shadow and masks
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it ([§1.5](CPU_DATA_ANALYSIS_IMAGE.md)), masks pixels its frames show to be defective
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([§1.6](CPU_DATA_ANALYSIS_IMAGE.md)), measures the beam centre from the isotropy of the
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scattered background and compares it with the file's ([§1.4](CPU_DATA_ANALYSIS_IMAGE.md)), and
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reads how wide this crystal's spots are, which sets the integration radius
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([§9.5](CPU_DATA_ANALYSIS_INTEGRATION.md)), and how much longer they are along their radius than
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across it, which is the beam's bandwidth where the file does not state one
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([§9.6](CPU_DATA_ANALYSIS_INTEGRATION.md)), and how much wider still they grow away from the beam,
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which sets the integration footprint ([§9.1](CPU_DATA_ANALYSIS_INTEGRATION.md)). In a GPU build the
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pre-scan runs on the card.
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**Spots.** Every image is decoded — on the GPU straight from the compressed chunk
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([§0](CPU_DATA_ANALYSIS_IMAGE.md)) — and one fused pass computes the azimuthal profile and finds
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the spots against each image's own per-resolution-ring noise
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([§2–§3](CPU_DATA_ANALYSIS_IMAGE.md)). The ice-ring score is read off the same profile.
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**Indexing.** The spots of a sample of frames are rotated back to a common crystal frame and the
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FFT search looks for periodicity over thousands of directions; candidate cells are
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Niggli-reduced, classified by Bravais lattice, refined both constrained and triclinic, and decided
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on how many validation frames each actually indexes
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([§4–§7](CPU_DATA_ANALYSIS_INDEXING.md)). A de-novo run also tries a second hypothesis with the
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shortest accepted axis lowered from 10 to 5 Å, for small-molecule cells. The first pass is indexed a
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second time at the beam centre the pre-scan measured; the file's centre is kept unless it indexes
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nothing, gives an axis harmonic of the measured centre's lattice, or loses to it when both first passes
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are merged ([§1.4](CPU_DATA_ANALYSIS_IMAGE.md)). A failed pass triggers the discrete rescues — the
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rotation-axis sign, the first-pass depth ladder, the long-axis rescue — before anything is given up on.
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**First integration pass.** At the geometry in the file, every frame of the first half of the sweep
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(`--prepass-fraction`) is predicted
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([§8](CPU_DATA_ANALYSIS_INTEGRATION.md)) and profile-fit integrated
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([§9](CPU_DATA_ANALYSIS_INTEGRATION.md)); partials are combined into fulls, scaled and merged
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([§10](CPU_DATA_ANALYSIS_INTEGRATION.md)).
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**Geometry post-refinement.** From those reflections the detector distance, beam centre and the
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cell scale / rotation axis are refined over all those frames at once, each step committed only if it
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improves a held-out residual ([§7.5](CPU_DATA_ANALYSIS_INDEXING.md)).
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**Second pass.** The sweep is re-indexed de novo and re-integrated at the refined geometry; this
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pass is the canonical output, and a guard compares the two passes and keeps the better one
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(reported as `PASS=` / `PASS_DECISION=` in [the report](RUGNUX_REPORT.md)).
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**Space group.** On the P1 merge of the final pass, the point group is scored operator by operator
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on resolution-normalised intensities and the screw axes, glide planes and centring are read from the
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systematic absences, with the centre of symmetry from the intensity distribution where the absences
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leave it open ([§13.1](CPU_DATA_ANALYSIS_DECISIONS.md)); twinning and translational
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pseudo-symmetry are checked beside it ([§13.2](CPU_DATA_ANALYSIS_DECISIONS.md)). `CANNOT_DETERMINE` and an enantiomorphic pair are real
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answers here, not evasions.
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**Scale and merge.** In the determined group: per-frame scales, the cross-validated correction
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surfaces (decay, absorption, modulation), the error model and ISa, outlier rejection, the
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CC1/2-based resolution cut, the anisotropy description, French–Wilson amplitudes and the R-free
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flags ([§10](CPU_DATA_ANALYSIS_INTEGRATION.md),
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[§13.3–§13.5](CPU_DATA_ANALYSIS_DECISIONS.md)).
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**Write.** The merged `.mtz` / `.cif` / `.hkl`, the unmerged MTZ, the P1 cross-check and the
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results report land next to each other ([Output files](RUGNUX_TUTORIAL.md#output-files)); with
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`--model`, validation runs first and the maps and the placed model are written too
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([§14](CPU_DATA_ANALYSIS_DECISIONS.md)).
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**Stills instead.** Serial data skip the two-pass machinery: each image is indexed independently
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(with the known-cell `ffbidx` indexer where a cell is given), partiality comes from a per-crystal
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orientation-tilt post-refinement rather than a rocking curve, and a merohedral indexing ambiguity
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has to be broken per image, at integration time, against a reference or a model
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([Advanced ▸ the indexing ambiguity](RUGNUX_ADVANCED.md#the-indexing-ambiguity)).
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