wyj
2fc2b43e8d
Preserve the protected full-catalog dummy run, its initial harness failure, input and output hashes, distribution quantiles, and the resulting sparse-tile scheduling conclusions.
85 lines
4.1 KiB
Markdown
85 lines
4.1 KiB
Markdown
# Production chunk geometry diagnostic (2026-09-11)
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## Scope
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This run measures the event stream that the production HIP sink would receive
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for the supplied Schwarzschild Galactic-center render. `PSF_BACKEND=dummy`
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keeps the real imported lens map, all-sky prefetch, OpenMP dynamic triangle
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scheduling, inverse mapping, redshift/color/flux work, PSF cache eligibility,
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and 16,384-event per-worker chunk boundaries. It does not initialize HIP,
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allocate a full HDR framebuffer, splat pixels, or write PNG/FITS output.
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The run used repository revision `11e703e33dffb1ff168ba11dd922e68b448116b9`
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plus the uncommitted dummy-backend work. The complete stdout/stderr, executable
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and input hashes, process resource use, and protected-output hashes are in
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[`full_catalog.log`](full_catalog.log). An initial harness-only failure before
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the renderer started is retained as
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[`full_catalog_missing_time.log`](full_catalog_missing_time.log).
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## Build and run
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```sh
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make -j1 PSF_BACKEND=dummy SPACETIME=schwarzschild ENABLE_HDR=1 backend
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python3 benchmarks/dummy_psf_chunks_2026-09-11/run.py
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```
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The runner fixes `OMP_NUM_THREADS=16` and `OMP_DYNAMIC=FALSE`, uses a 600-second
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timeout and a process lock, refuses to overwrite its log, and hashes both the
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named PNG and companion FITS before and after the run. Its renderer arguments
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are exactly the user-supplied command except that the `_hip` executable is
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replaced by `_dummy`; the exact expanded command is the first line of the log.
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Inputs and protected outputs:
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- lens map SHA-256:
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`905f960aea2d276f9586c79fba545a72cf742311e9e7e18faea293835c68bf28`
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- existing PNG SHA-256 before/after:
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`3e01feb911e60acce545a6a86870ca05f96250022e874eb8097bec88a8879bfd`
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- existing FITS SHA-256 before/after:
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`2408e62dcc22f147da284d87af9a2b0fdd0050eda2dabc23b6ec2554b2f1d38e`
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Both protected files retained the same size and nanosecond mtime as well as the
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same hash. No HIP backend was run.
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## Result
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The catalog prefetch loaded 343,363,141 stars for 130,882 lens triangles. The
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producer classified 598,264,924 cache events, with zero direct fallbacks,
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wing-clipped events, or min-Y discards. Sixteen workers produced 36,524 chunks:
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36,508 full chunks and one final partial chunk per worker.
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| full-chunk metric | min | p10 | p25 | p50 | p75 | p90 | p99 | max |
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|---|---:|---:|---:|---:|---:|---:|---:|---:|
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| event-producing triangles | 1 | 1 | 1 | 2 | 3 | 10 | 31 | 59 |
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| occupied 32px center tiles | 1 | 1 | 1 | 1 | 2 | 5 | 30 | 45 |
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| event bbox diagonal (px) | 0.199 | 0.742 | 3.250 | 12.651 | 57.018 | 429.306 | 3759.261 | 3834.557 |
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| triangle-centroid bbox diagonal (px) | 0 | 0 | 0 | 9.618 | 49.477 | 424.149 | 3744.061 | 3824.075 |
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| maximum successive centroid jump (px) | 0 | 0 | 0 | 8.724 | 25.157 | 144.000 | 3744.034 | 3792.034 |
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All 36,508 full chunks satisfy the replay prototype's current selector:
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`events >= 8192 && events / occupied_32px_tiles >= 32`.
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Catalog prefetch took 55.469 s. Producer classification and chunk accounting
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took 232.340 s; total process wall time was 288.872 s. These are diagnostic CPU
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costs and do not estimate HIP tile-kernel speed.
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## Interpretation and limits
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The measured production event order strongly supports the hypothesis that a
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full worker chunk is usually filled by very few image-plane triangles: the
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median is two and 75% contain at most three. Center-tile occupancy is even more
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concentrated. This is favorable for a tile16 path because the same output pixels
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receive many contributions that can be reduced before the final double HDR
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write.
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The rare tail matters: p99 chunks can contain a few clusters separated by
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nearly the full 4K image width. “Few triangles” therefore does not imply one
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small contiguous bounding rectangle. A production implementation should use a
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sparse occupied-tile list, retain the atomic fallback, and measure the complete
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streaming sink including binning and synchronization.
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This is one Schwarzschild Galactic-center frame with one 16-worker dynamic
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schedule. Worker-to-triangle assignment is nondeterministic, so exact quantiles
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may vary between runs. The result establishes event geometry for this input; it
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does not by itself establish single-BH/BBH universality or a HIP speedup.
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