Fast2DC

Fast 2D-C, probetype 3 – its own timing family, sharing the PMS reader with probetype 0. Same stage-4 path under v3.5 as the 2D-C and 2D-P.

The instrument, as the code sees it

Every row below is read from constants.IMGPROC_CONFIG, the port of imgProc_sm.m's own probe switch. None of it is typed into this page.

What runs today

Imported from the coverage matrix rather than restated, so this table and docs/developer/COVERAGE_MATRIX.md cannot disagree.

How to read this table.

• VALIDATED – the output was compared with an archived product the original code wrote, and every difference is accounted for.
• CROSS-CHECKED – the path runs, and its code is asserted against the original MATLAB/IDL executing under Octave/GDL – on fixtures, not necessarily on real data from this instrument.
• unvalidated – the path runs, but nothing independent has been compared with its output.
• refuses (by design) – the driver stops with a message, because the combination is meaningless or out of that engine's scope.
• refused (not built) – the driver stops with a message because the code for the combination has not been written; nothing known makes it impossible.
• REFUSES (DEFECT) – the driver stops with a message, but the combination should work and does not yet.
• untested – no test exercises this combination, so nothing is claimed either way.
• serial column – one process, the reference way to run.
• --chunks column – stage 3 (image processing) of each file split across N processes and merged.
• --jobs column – N raw files processed at once, one process each.
• --s2-jobs column – stage 2 (the raw decode) of one large file split across N processes.
• --jit column – stage 3's hottest per-particle kernels compiled with numba.
• arrayprobe_uiops – the UIOOPS v3.5 port, the default for new work.
• arrayprobe_soda2 – the SODA-2 port.

No shipped preset names this probe. A run needs a campaign preset declared in your own TOML ([run].presets), and [run].preset is required – it has no default.

Where a cell above reads refuses (by design) or REFUSES (DEFECT), the reason is in docs/developer/COVERAGE_MATRIX.md for that exact cell. A refusal here is always preferred to a silently wrong fast answer, and the two words are different: by design means the combination is meaningless, defect means it should work and does not yet.

Caveats

Consequences of this probe's own geometry

Computed from the table above, not recalled – each says which arithmetic produced it.

The hollow test only packs diodes 1-32, and this array has 64

calculate_reject_unified.m:465 packs diodes 1-32 whatever the probe's width. This probe is 64 diodes wide, so a particle imaged entirely beyond diode 32 gives the test two zero operands and is ruled hollow on no evidence. That verdict reaches auto_reject AND the Korolev correction, so it moves both acceptance and recorded size. Preserved deliberately; wide_hollow_fix in enhancements_uiops/ is the opt-in, default-off alternative, and v3.5's own rewrite is a DIFFERENT correction from ours (it also drops the middle-third scan restriction – 745 of 1,080 random particles disagree).

Computed from: constants.IMGPROC_CONFIG['Fast2DC'].diodenum = 64

The array images 1.6 mm, and a size ladder must respect that

64 diodes at 0.025 mm is 1.6 mm across. That is not a hard ceiling on recorded size, and it would be an overclaim to say so: a particle that merely has its centre in the array (sa_method 0) or is sized through the Heymsfield & Parrish reconstruction (sa_method 2) can be recorded LARGER than the array it crossed. The bound that survives is a factor, not an equality – a centre-in particle reaches about twice the array width, not twenty times it. So the honest reading is: a bin above roughly 3.2 mm on this probe is beyond what any sizing convention here produces, and a ladder whose top lies there is a configuration error rather than a sparse flight. The upstream finding that the default 2D-S bin table became the HVPS one (recorded in the review of the upstream code) is exactly that: a 30 mm ladder handed to a 1.28 mm array, 23x its width, and the symptom was a well-formed file with almost nothing in it.

Computed from: constants.IMGPROC_CONFIG['Fast2DC']: diodenum 64 x ds 0.025 mm = 1.6 mm

Chunked stage 3: supported

Timing family fast2dc is in CHUNKABLE_TIMINGS_V35, so --chunks splits stage 3 with no carried state and the result is byte-identical to a serial run.

Computed from: constants.IMGPROC_CONFIG['Fast2DC'].timing = 'fast2dc'; CHUNKABLE_TIMINGS_V35 = ('dmt', 'pms', 'fast2dc'); PRIMABLE_TIMINGS_V35 = ('spec',)

What a person knows and a constant does not

Curated in probe_caveats.json (in scripts/). Every citation is re-checked against the real file each time this page is generated.

SODA-2 runs the RAF Fast-2DC path, identical to SODA-2's IDL on a real file

The SODA-2 engine ports the RAF reader (soda2_read2dbuffer.pro:19-66) and the Fast-2DC buffer processing for probetype F2DC_v2 (soda2_processbuffer.pro:28-78). The buffer step matches the original IDL under GDL on 10 synthetic buffers, and on a real file (CAESAR 2024 rf05, probe C4, 35480-35540 s) the serial driver's output is identical to soda2_process_2d.pro run under GDL in all eight fields compared (TIME, TAS, SPEC2D, COUNT_ACCEPTED, ACTIVETIME, INTSPEC_ALL, COUNT_MISSED, MISSED_HIST). The check is against SODA-2's own code, not an archived product; --jobs above 1 is refused by name.

Source: tests/test_soda2_raf_realfile_gdl.py

Probetype 3 has its own timing family, and stage 2 opens it

It reads through read_binary_PMS like probetype 0 but carries timing='fast2dc', so it is not simply a 2D-C with a different pitch. The driver's stage 2 (the raw decode) accepts it, and v3.5's stage 4 runs it (the SOCRATES Fast2DC and catch-all F2DC arms, checked against Octave on synthetic input).

Source: src/arrayprobe/driver/run_flight.py

Reject code 't' is never emitted, on any probe

calculate_reject_unified.m:269 rejects on the tighter threshold (max_comp_img_ar) before :272 tests the looser one (max_edge_img_ar), so the second branch is unreachable and image_auto_reject never contains 116. The netCDF Description attribute at imgProc_sm.m:325-329 states the two thresholds the other way round. Both are preserved verbatim – this is a faithfully reproduced upstream defect, not a port bug. If you are tabulating reject codes, 't' is structurally absent rather than merely rare.

Trust the .call sidecar, not the filename

Every stage stamps its configuration into a .call sidecar and refuses an input that disagrees or carries no stamp. If you write products with your own script instead of arrayprobe run, you inherit this problem.

Ratios this probe appears in

None. No ratio measured so far has this probe on either side – which follows from the data held: a ratio needs two chains over the same raw, and there is no raw here to run two chains over.

Where to go next

Generated, not hand-maintained, from arrayprobe.constants.IMGPROC_CONFIG, coverage_matrix.build_matrix() and the curated caveats in probe_caveats.json.