wyj
e4d093a9fe
Add the production-density 4K Galactic-center comparison to the 2026-09-25 benchmark record, including the per-image error decomposition, and refine the fast-mode positioning in usage.md, the design document, and README. - Document that nearest/bilinear deposit accuracy is set by the deposit mode and N rather than output resolution, and that the still-frame error is dominated by a small number of resolved bright cores while the flux-dominant faint texture is much better than the global relative L2. - Add the temporal-coherence caveat: nearest deposition jumps by 1/N output pixel per axis across supersampled-cell boundaries, so fast mode is not qualified as a temporally coherent movie path; bilinear removes the centroid jump but broadens the profile. - Add scripts/fast_mode_error_decomposition.py, which ranks the largest |fast-base| RGB samples and partitions the error by a disjoint base-value range.
510 lines
26 KiB
Markdown
510 lines
26 KiB
Markdown
# Fast-mode FFTW convolution benchmark (2026-09-25)
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Replaces the spatial fast-mode global convolution with a reusable FFTW linear
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convolution. This record separates one-time plan/setup from steady-state
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execution and repeats the bounded Galactic-center comparison. Raw resolver and
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end-to-end output is pasted verbatim from the runs below.
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The later production-density 4K comparison is recorded separately against the
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first committed FFTW implementation, revision
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`229f50cd864d9768324042c10edbb56bfc120f08`.
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## Environment
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- Git revision: `3deebfb` plus the uncommitted FFTW work.
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- Host: 12th Gen Intel Core i7-12700K, 16 hardware threads, 128 GB.
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- FFTW: `pkg-config --modversion fftw3_omp` = `3.3.10`;
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`pkg-config --libs fftw3_omp` = `-lfftw3_omp -lfftw3`.
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- Build:
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`make -j8 BUILD_TYPE=Release PSF_BACKEND=cpu SPACETIME=minkowski backend`
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(`-O2 -DNDEBUG -fopenmp -march=native`, libpng, `-DFAST_PSF_FFTW`).
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- Binary SHA-256 (this run):
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- `build/Release/minkowski_sky`:
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`ead2a543b8166abe6f82bc1cd41b2e985a6db517aa45a6416d08d188138b8c47`
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- `build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw`:
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`8da8bbd532104a0c4f524aabf40b66a50c8c715e44479c7db467669ab5a21215`
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- Timing wrapper: `/usr/bin/time` is not installed on this host. The
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reproducible wrapper used for the end-to-end runs is zsh's built-in `time`
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with `TIMEFMT='real=%*E user=%U sys=%S cpu=%P'`, i.e. each command was run as
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`TIMEFMT='real=%*E user=%U sys=%S cpu=%P'; time <command>`. The `real=...`
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lines below are the verbatim wrapper output.
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## Correctness
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```sh
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make -j8 BUILD_TYPE=Debug PSF_BACKEND=cpu SPACETIME=minkowski test
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```
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All C tests pass, including the dedicated FFTW-vs-spatial test (258 comparisons
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over sizes `17x13`/`16x16`/`23x31`/`33x17`, `N = 1..4`, nearest and bilinear,
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eight scenes; worst `max_abs = 1.8e-14`), the `test_frame` fast-mode
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regressions, the non-fast FITS references, and both camera CLI checks. HIP and
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dummy renderers compile and link without FFTW; `make PSF_BACKEND=dummy test`
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now fails fast with `make test requires PSF_BACKEND=cpu` instead of reusing a
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stale CPU test binary.
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## Resolver-only benchmark
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One deterministic sparse impulse buffer, default PSF (FWHM 2.7, beta 4.5,
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relative tail 1e-8), `OMP_NUM_THREADS=16`. `--spatial` additionally runs the
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reference resolver on the identical buffer. Binary:
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`build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw`.
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### Default 320x240 N=2, FFTW_ESTIMATE
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```sh
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OMP_NUM_THREADS=16 ./build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw \
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--width 320 --height 240 --supersample 2 --repeats 7 --spatial
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```
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```text
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impulse: 320x240 supersample=2 deposit=nearest repeats=7 spatial=1
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plan_mode=estimate
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setup: init=0.039444 s fftw_plan=0.008085 s kernel_fft=0.005237 s
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Fast FFTW: linear min=666x826, fft=672x840, workers=16, plan=estimate, plan=0.008085 s, kernel_fft=0.005237 s, scratch=30.2 MiB
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impulse_hash=5334fa90cfbb1089
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fftw: min=0.005602 s median=0.006455 s max=0.008144 s
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fftw samples: 0.006697 0.005784 0.005602 0.005898 0.006455 0.007675 0.008144
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fftw_hdr_hash=9ad60d92992c9bbd
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spatial: 0.702470 s
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spatial_hdr_hash=9327ac3e8e10d670
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difference: max_abs=7.49e-16 peak=0.359 speedup=108.831x
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rss_max_kb=52908
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```
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### Default 320x240 N=4, FFTW_ESTIMATE
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```sh
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OMP_NUM_THREADS=16 ./build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw \
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--width 320 --height 240 --supersample 4 --repeats 7 --spatial
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```
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```text
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impulse: 320x240 supersample=4 deposit=nearest repeats=7 spatial=1
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plan_mode=estimate
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setup: init=0.114719 s fftw_plan=0.007169 s kernel_fft=0.011942 s
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Fast FFTW: linear min=1330x1650, fft=1344x1680, workers=16, plan=estimate, plan=0.007169 s, kernel_fft=0.011942 s, scratch=120.7 MiB
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impulse_hash=2639864ea9d3a26a
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fftw: min=0.034756 s median=0.039591 s max=0.042474 s
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fftw samples: 0.041352 0.039591 0.034756 0.040866 0.042474 0.035364 0.036241
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fftw_hdr_hash=1ff070fdaac85f4a
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spatial: 11.054385 s
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spatial_hdr_hash=7682ee8550f88efe
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difference: max_abs=5.38e-15 peak=0.533 speedup=279.214x
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rss_max_kb=161032
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```
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### Medium 960x540 N=2, FFTW_ESTIMATE (FFTW only)
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```sh
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OMP_NUM_THREADS=16 ./build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw \
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--width 960 --height 540 --supersample 2 --repeats 7
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```
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```text
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impulse: 960x540 supersample=2 deposit=nearest repeats=7 spatial=0
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plan_mode=estimate
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setup: init=0.042270 s fftw_plan=0.006317 s kernel_fft=0.010302 s
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Fast FFTW: linear min=1266x2106, fft=1280x2160, workers=16, plan=estimate, plan=0.006317 s, kernel_fft=0.010302 s, scratch=147.7 MiB
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impulse_hash=6e2de17f6859cd33
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fftw: min=0.038361 s median=0.039872 s max=0.055834 s
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fftw samples: 0.055834 0.038745 0.039872 0.038823 0.038361 0.048436 0.040141
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fftw_hdr_hash=c493dbb793d04706
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rss_max_kb=216272
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```
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### 4K 3840x2160 N=2, FFTW_ESTIMATE (FFTW only)
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```sh
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OMP_NUM_THREADS=16 ./build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw \
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--width 3840 --height 2160 --supersample 2 --repeats 5
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```
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```text
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impulse: 3840x2160 supersample=2 deposit=nearest repeats=5 spatial=0
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plan_mode=estimate
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setup: init=0.524840 s fftw_plan=0.008154 s kernel_fft=0.482906 s
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Fast FFTW: linear min=4506x7866, fft=4536x7875, workers=16, plan=estimate, plan=0.008154 s, kernel_fft=0.482906 s, scratch=1907.8 MiB
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impulse_hash=e3b6d7f3d621630d
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fftw: min=2.368634 s median=2.481927 s max=2.553895 s
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fftw samples: 2.552212 2.553895 2.481927 2.389895 2.368634
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fftw_hdr_hash=1c5720f72a040e6d
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rss_max_kb=2879596
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```
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### 4K 3840x2160 N=4, FFTW_ESTIMATE (FFTW only)
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```sh
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OMP_NUM_THREADS=16 ./build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw \
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--width 3840 --height 2160 --supersample 4 --repeats 5
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```
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```text
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impulse: 3840x2160 supersample=4 deposit=nearest repeats=5 spatial=0
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plan_mode=estimate
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setup: init=0.738771 s fftw_plan=0.003636 s kernel_fft=0.599235 s
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Fast FFTW: linear min=9010x15730, fft=9072x15750, workers=16, plan=estimate, plan=0.003636 s, kernel_fft=0.599235 s, scratch=7631.4 MiB
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impulse_hash=e6a528db0fb16c33
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fftw: min=3.276609 s median=3.339285 s max=3.369411 s
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fftw samples: 3.309935 3.369411 3.276609 3.345614 3.339285
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fftw_hdr_hash=e55bed24ef3f5506
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rss_max_kb=10919208
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```
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### FFTW_ESTIMATE versus FFTW_MEASURE
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`FFTW_MEASURE` cuts steady-state time but costs a large one-time plan. Because
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the plan is created once per process and reused across frames, it only pays off
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for long movie renders; production therefore defaults to `FFTW_ESTIMATE`.
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Wisdom import/export would make `FFTW_MEASURE` the better default and remains a
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follow-up. Measured FFTW_MEASURE plan output is not bit-reproducible (plan
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measurement is timing-dependent), so its `fftw_hdr_hash` may differ run to run;
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the spatial comparison stays at roundoff.
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```sh
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OMP_NUM_THREADS=16 ./build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw \
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--width 320 --height 240 --supersample 2 --repeats 7 --measure --spatial
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```
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```text
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impulse: 320x240 supersample=2 deposit=nearest repeats=7 spatial=1
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plan_mode=measure
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setup: init=1.584388 s fftw_plan=1.091687 s kernel_fft=0.467405 s
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Fast FFTW: linear min=666x826, fft=672x840, workers=16, plan=measure, plan=1.091687 s, kernel_fft=0.467405 s, scratch=30.2 MiB
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impulse_hash=5334fa90cfbb1089
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fftw: min=0.003995 s median=0.004702 s max=0.005804 s
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fftw samples: 0.003995 0.004702 0.004330 0.005804 0.004939 0.004986 0.004619
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fftw_hdr_hash=626e386cba92ffa5
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spatial: 0.706244 s
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spatial_hdr_hash=9327ac3e8e10d670
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difference: max_abs=8.05e-16 peak=0.359 speedup=150.198x
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rss_max_kb=51860
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```
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```sh
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OMP_NUM_THREADS=16 ./build/Release/obj/minkowski/standard_sink1_cpu/benchmark_fast_psf_fftw \
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--width 3840 --height 2160 --supersample 2 --repeats 5 --measure
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```
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```text
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impulse: 3840x2160 supersample=2 deposit=nearest repeats=5 spatial=0
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plan_mode=measure
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setup: init=41.408673 s fftw_plan=41.239987 s kernel_fft=0.134272 s
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Fast FFTW: linear min=4506x7866, fft=4536x7875, workers=16, plan=measure, plan=41.239987 s, kernel_fft=0.134272 s, scratch=1907.8 MiB
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impulse_hash=e3b6d7f3d621630d
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fftw: min=0.518707 s median=0.522181 s max=0.539465 s
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fftw samples: 0.523380 0.539465 0.518707 0.520357 0.522181
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fftw_hdr_hash=ab90c4b076c775e1
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rss_max_kb=2884132
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```
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## End-to-end bounded comparison
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Same catalog, geometry, exposure, supersample factors, and worker environment as
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`benchmarks/fast_mode_cpu_2026-09-18.md`. Raw terminal output including the
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timing wrapper:
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```sh
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OMP_NUM_THREADS=16 TIMEFMT='real=%*E user=%U sys=%S cpu=%P' \
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time ./build/Release/minkowski_sky --all-sky-catalog assets/2mass/processed/all_sky \
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--width 320 --height 240 --fov-deg 10 --look-ra-deg 266 --look-dec-deg -29 \
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--exposure 1e13 --coarse-cell-pixels 16 --refine-max-level 0 \
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--output /tmp/opencode/fastmode_fftw_bench/normal.png
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```
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```text
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Blackbody LUT: 1024 CIE 1931 2-deg 1 nm-linear XYZ nodes, T=[670.146556, 101408.88] K, loaded assets/blackbody/cie1931_2deg_xyz_1024.grbblut in 0.000046 s; payload fnv1a64=0e39867b0e70a809
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Blackbody backend: lut
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PSF cache ready: 64x64 phases, radius 47 px, relative tail 1e-08, tail abs 1e-06, boundary 1e-07, build 0.776 s
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Catalog prefetch: 96 requested, 96 newly loaded (6618807 stars), 0 unavailable in 0.729 s; 4 loader workers
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Rendered 5912840 images from 6618807 catalog stars to /tmp/opencode/fastmode_fftw_bench/normal.png (ok)
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PSF splats: cached 5912840, cached wing-clipped 0, direct fallbacks 0, discarded below min-Y 0
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real=17.526 user=225.46s sys=2.44s cpu=1300%
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```
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```sh
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OMP_NUM_THREADS=16 TIMEFMT='real=%*E user=%U sys=%S cpu=%P' \
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time ./build/Release/minkowski_sky --all-sky-catalog assets/2mass/processed/all_sky \
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--width 320 --height 240 --fov-deg 10 --look-ra-deg 266 --look-dec-deg -29 \
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--exposure 1e13 --coarse-cell-pixels 16 --refine-max-level 0 \
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--fast-mode --fast-supersample 2 \
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--output /tmp/opencode/fastmode_fftw_bench/fast_n2.png
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```
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```text
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Fast mode is a preview approximation; --max-cache-psf-flux is ignored and one global kernel is used for every event.
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Blackbody LUT: 1024 CIE 1931 2-deg 1 nm-linear XYZ nodes, T=[670.146556, 101408.88] K, loaded assets/blackbody/cie1931_2deg_xyz_1024.grbblut in 0.000049 s; payload fnv1a64=0e39867b0e70a809
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Blackbody backend: lut
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Fast PSF: supersample 2x, deposit nearest, kernel radius 93 ss px (46.50 final px), retained flux 1.000000, cached 4-point quadrature
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Fast FFTW: linear min=666x826, fft=672x840, workers=16, plan=estimate, plan=0.007770 s, kernel_fft=0.005020 s, scratch=30.2 MiB
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Catalog prefetch: 96 requested, 96 newly loaded (6618807 stars), 0 unavailable in 0.735 s; 4 loader workers
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Rendered 5912840 images from 6618807 catalog stars to /tmp/opencode/fastmode_fftw_bench/fast_n2.png (ok)
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Fast PSF splats: deposited 5912840, wing-clipped 0, discarded below min-Y 0
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real=0.995 user=5.30s sys=0.18s cpu=550%
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```
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```sh
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OMP_NUM_THREADS=16 TIMEFMT='real=%*E user=%U sys=%S cpu=%P' \
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time ./build/Release/minkowski_sky --all-sky-catalog assets/2mass/processed/all_sky \
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--width 320 --height 240 --fov-deg 10 --look-ra-deg 266 --look-dec-deg -29 \
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--exposure 1e13 --coarse-cell-pixels 16 --refine-max-level 0 \
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--fast-mode --fast-supersample 4 \
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--output /tmp/opencode/fastmode_fftw_bench/fast_n4.png
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```
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```text
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Fast mode is a preview approximation; --max-cache-psf-flux is ignored and one global kernel is used for every event.
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Blackbody LUT: 1024 CIE 1931 2-deg 1 nm-linear XYZ nodes, T=[670.146556, 101408.88] K, loaded assets/blackbody/cie1931_2deg_xyz_1024.grbblut in 0.000044 s; payload fnv1a64=0e39867b0e70a809
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Blackbody backend: lut
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Fast PSF: supersample 4x, deposit nearest, kernel radius 185 ss px (46.25 final px), retained flux 1.000000, cached 4-point quadrature
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Fast FFTW: linear min=1330x1650, fft=1344x1680, workers=16, plan=estimate, plan=0.007294 s, kernel_fft=0.012307 s, scratch=120.7 MiB
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Catalog prefetch: 96 requested, 96 newly loaded (6618807 stars), 0 unavailable in 0.722 s; 4 loader workers
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Rendered 5912840 images from 6618807 catalog stars to /tmp/opencode/fastmode_fftw_bench/fast_n4.png (ok)
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Fast PSF splats: deposited 5912840, wing-clipped 0, discarded below min-Y 0
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real=1.033 user=5.56s sys=0.22s cpu=559%
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```
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Image counts are identical across normal and both fast runs (5,912,840), so the
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FFTW resolver did not change catalog/deposit behavior. Output SHA-256:
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```text
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normal.png e9f0a98ae7a3c3db546a3f276f400be98c96446fab7bfbc632f388702d4722d1
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fast_n2.png 1f144aefb4a5520d9d76a13ab69026a72580663e5e45f53128a87a0801176ccf
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fast_n4.png 679f14a67a085f76c144ecbe36af51b3b2534c152e8ef59708a7884a3f7c8464
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```
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## Production-density 4K Galactic-center comparison
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This is the full 3840x2160, 50-degree-field run over the local processed 2MASS
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all-sky catalog, not the bounded 320x240 comparison above.
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### Provenance
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- Git revision: `229f50cd864d9768324042c10edbb56bfc120f08`
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(`Feat: Use FFTW linear convolution for CPU fast-mode PSF resolve`).
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- The tracked worktree matched that revision when this record was written; the
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unrelated untracked `nmesh_spacetime_output_format.md` was not an input.
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- Executable: `build/Release/minkowski_sky`, built at
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`2026-09-25 23:16:45 -0400`, before the three runs below; size 146,856 bytes;
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SHA-256
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`7f6486285b2ff498adb2d4f1acaf62dc96b11125c9cec114f572b9379648962c`.
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A Make dry-run after the commit requested only the Makefile's unconditional
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`FORCE` relink and no object recompilation, so the recorded binary used the
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object set corresponding to the committed tracked sources.
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- Host: 12th Gen Intel Core i7-12700K, 16 hardware threads, 128 GB. The commands
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did not explicitly set `OMP_NUM_THREADS`; fast-mode initialization reported
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`workers=16`.
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- Input: `assets/2mass/processed/all_sky`, observed when recording as 64,801
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regular files and 16,207,861,727 bytes. The renderer selected 1,742 tiles and
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loaded 54,509,992 stars in each run. No content manifest hash was recorded for
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this external processed catalog.
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- Timing: zsh built-in `time`; its final timing line is included verbatim for
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each command.
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### Standard cached spatial PSF
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```sh
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time ./build/Release/minkowski_sky \
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--psf-relative-tail 1e-6 --psf-min-y 1e-8 --max-cache-psf-flux 1e8 \
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--all-sky-catalog assets/2mass/processed/all_sky \
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--width 3840 --height 2160 \
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--look-ra-deg 262.5 --look-dec-deg -30 \
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--fov-deg 50 \
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--coarse-cell-pixels 16 \
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--exposure 1e13 \
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--psf-fwhm-pixels 2.7 --psf-moffat-beta 3 \
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--catalog-load-workers 4 \
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--hdr-output \
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--output output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-base.png
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```
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```text
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Blackbody LUT: 1024 CIE 1931 2-deg 1 nm-linear XYZ nodes, T=[670.146556, 101408.88] K, loaded assets/blackbody/cie1931_2deg_xyz_1024.grbblut in 0.000130 s; payload fnv1a64=0e39867b0e70a809
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Blackbody backend: lut
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PSF cache ready: 64x64 phases, radius 85 px, relative tail 1e-06, tail abs 1e-06, boundary 1e-07, build 2.176 s
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Catalog prefetch: 1742 requested, 1742 newly loaded (54509992 stars), 0 unavailable in 5.886 s; 4 loader workers
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Rendered 52544535 images from 54509992 catalog stars to output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-base.png (ok)
|
|
PSF splats: cached 52477581, cached wing-clipped 0, direct fallbacks 0, discarded below min-Y 66954
|
|
Warning: --psf-min-y discarded one or more PSF events.
|
|
./build/Release/minkowski_sky --psf-relative-tail 1e-6 --psf-min-y 1e-8 1e8 938.60s user 15.80s system 1391% cpu 1:08.61 total
|
|
```
|
|
|
|
### Fast mode, N=2
|
|
|
|
```sh
|
|
time ./build/Release/minkowski_sky --fast-mode --fast-supersample 2 \
|
|
--psf-relative-tail 1e-6 --psf-min-y 1e-8 --max-cache-psf-flux 1e8 \
|
|
--all-sky-catalog assets/2mass/processed/all_sky \
|
|
--width 3840 --height 2160 \
|
|
--look-ra-deg 262.5 --look-dec-deg -30 \
|
|
--fov-deg 50 \
|
|
--coarse-cell-pixels 16 \
|
|
--exposure 1e13 \
|
|
--psf-fwhm-pixels 2.7 --psf-moffat-beta 3 \
|
|
--catalog-load-workers 4 \
|
|
--hdr-output \
|
|
--output output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-2.png
|
|
```
|
|
|
|
```text
|
|
Fast mode is a preview approximation; --max-cache-psf-flux is ignored and one global kernel is used for every event.
|
|
Blackbody LUT: 1024 CIE 1931 2-deg 1 nm-linear XYZ nodes, T=[670.146556, 101408.88] K, loaded assets/blackbody/cie1931_2deg_xyz_1024.grbblut in 0.000101 s; payload fnv1a64=0e39867b0e70a809
|
|
Blackbody backend: lut
|
|
Fast PSF: supersample 2x, deposit nearest, kernel radius 169 ss px (84.50 final px), retained flux 0.999999, cached 4-point quadrature
|
|
Fast FFTW: linear min=4658x8018, fft=4704x8064, workers=16, plan=estimate, plan=0.005275 s, kernel_fft=0.141445 s, scratch=2026.1 MiB
|
|
Catalog prefetch: 1742 requested, 1742 newly loaded (54509992 stars), 0 unavailable in 5.873 s; 4 loader workers
|
|
Rendered 52544535 images from 54509992 catalog stars to output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-2.png (ok)
|
|
Fast PSF splats: deposited 52477581, wing-clipped 0, discarded below min-Y 66954
|
|
./build/Release/minkowski_sky --fast-mode --fast-supersample 2 1e-6 1e-8 115.74s user 2.08s system 763% cpu 15.439 total
|
|
```
|
|
|
|
### Fast mode, N=4
|
|
|
|
```sh
|
|
time ./build/Release/minkowski_sky --fast-mode --fast-supersample 4 \
|
|
--psf-relative-tail 1e-6 --psf-min-y 1e-8 --max-cache-psf-flux 1e8 \
|
|
--all-sky-catalog assets/2mass/processed/all_sky \
|
|
--width 3840 --height 2160 \
|
|
--look-ra-deg 262.5 --look-dec-deg -30 \
|
|
--fov-deg 50 \
|
|
--coarse-cell-pixels 16 \
|
|
--exposure 1e13 \
|
|
--psf-fwhm-pixels 2.7 --psf-moffat-beta 3 \
|
|
--catalog-load-workers 4 \
|
|
--hdr-output \
|
|
--output output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-4.png
|
|
```
|
|
|
|
```text
|
|
Fast mode is a preview approximation; --max-cache-psf-flux is ignored and one global kernel is used for every event.
|
|
Blackbody LUT: 1024 CIE 1931 2-deg 1 nm-linear XYZ nodes, T=[670.146556, 101408.88] K, loaded assets/blackbody/cie1931_2deg_xyz_1024.grbblut in 0.000043 s; payload fnv1a64=0e39867b0e70a809
|
|
Blackbody backend: lut
|
|
Fast PSF: supersample 4x, deposit nearest, kernel radius 336 ss px (84.00 final px), retained flux 0.999999, cached 4-point quadrature
|
|
Fast FFTW: linear min=9312x16032, fft=9375x16128, workers=16, plan=estimate, plan=0.005384 s, kernel_fft=0.743673 s, scratch=8075.5 MiB
|
|
Catalog prefetch: 1742 requested, 1742 newly loaded (54509992 stars), 0 unavailable in 5.796 s; 4 loader workers
|
|
Rendered 52544535 images from 54509992 catalog stars to output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-4.png (ok)
|
|
Fast PSF splats: deposited 52477581, wing-clipped 0, discarded below min-Y 66954
|
|
./build/Release/minkowski_sky --fast-mode --fast-supersample 4 1e-6 1e-8 135.62s user 5.04s system 722% cpu 19.469 total
|
|
```
|
|
|
|
### Artifacts and comparison
|
|
|
|
```text
|
|
05517bde1383327043691ac4b713f638b03ebf6dc72207fe8710a8dce747a03e output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-base.png
|
|
86e9220feac277d77eba87aa8d0febadca5f4eea35cb56164a4eb1578b20fccd output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-2.png
|
|
5dfef3b4bd39d9809463594a1065c32c65ad397396514664c8aa22a5da6d780b output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-4.png
|
|
1ea508d1ee787c2e5f35ccdf37ca5f4a58e9ff5e9984b50928d66ecf88c44c3d output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-base_HDR.fits
|
|
71de3f1e11cb9f811f5d08ea45b51baf5968e8523873873d6f7c414c1849ba53 output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-2_HDR.fits
|
|
554848e39fdfb3b4815fb8f2a591b8d356cbdeaaea235a73f19b46017a18e42a output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-4_HDR.fits
|
|
```
|
|
|
|
All three runs produced 52,544,535 images and applied the same event filtering:
|
|
52,477,581 cached/deposited events, no wing clipping or direct fallback, and
|
|
66,954 events (0.12742334% of rendered images) discarded by `--psf-min-y`.
|
|
|
|
Using the standard HDR buffer as the reference, with
|
|
`relative_L2 = ||fast - base||_2 / ||base||_2`, the existing FITS artifacts give:
|
|
|
|
| Mode | Wall time | Wall speedup | Approx. speedup after subtracting catalog prefetch | User-CPU speedup | Scratch | HDR relative L2 | HDR total-flux ratio | Tone-mapped PNG normalized RMSE |
|
|
|---|---:|---:|---:|---:|---:|---:|---:|---:|
|
|
| Standard | 68.610 s | 1.000x | 1.000x | 1.000x | n/a | 0 | 1 | 0 |
|
|
| Fast N=2 | 15.439 s | 4.444x | 6.557x | 8.110x | 2026.1 MiB | 10.4384% | 1.000176588 | 0.00678916 |
|
|
| Fast N=4 | 19.469 s | 3.524x | 4.587x | 6.921x | 8075.5 MiB | 4.37249% | 1.000178510 | 0.00365798 |
|
|
|
|
The post-prefetch figures subtract only the renderer-reported catalog prefetch
|
|
duration from wall time; they are useful context, not isolated PSF timings. N=4
|
|
costs 26.1% more wall time and 3.986x the scratch of N=2, while reducing the HDR
|
|
relative-L2 difference by about 58% and the tone-mapped PNG RMSE by about 46%.
|
|
The nearly identical `+0.0177%` total-flux offset for N=2 and N=4 shows that the
|
|
larger N primarily improves spatial placement rather than global photometry.
|
|
For the intended rapid single-frame exposure/PSF preview, N=2 is therefore the
|
|
default throughput point; N=4 is the higher-fidelity preview option.
|
|
|
|
### Error distribution across the image
|
|
|
|
The unweighted relative L2 above is dominated by a small number of very bright
|
|
PSF cores, so it understates how well the dense faint-star texture is
|
|
reproduced in this still frame. `scripts/fast_mode_error_decomposition.py`
|
|
reports the error over the flattened scalar RGB channel samples:
|
|
|
|
```sh
|
|
python3 scripts/fast_mode_error_decomposition.py \
|
|
output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-base_HDR.fits \
|
|
output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-2_HDR.fits \
|
|
output/imgs/2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-4_HDR.fits
|
|
```
|
|
|
|
```text
|
|
===== 2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-2_HDR.fits ===== relative_L2=10.4384%
|
|
top |d| RGB samples: sq-error energy base energy linear-RGB sum sample share
|
|
top 0.0010%: 69.136% 48.948% 2.822% 0.0010%
|
|
top 0.0100%: 95.732% 87.994% 9.141% 0.0100%
|
|
top 0.1000%: 99.365% 97.633% 16.396% 0.1000%
|
|
top 1.0000%: 99.893% 99.224% 25.984% 1.0000%
|
|
top 10.0000%: 99.988% 99.679% 46.006% 10.0000%
|
|
base-value range (disjoint): rel_RMS signed bias base energy % linear-RGB sum % samples
|
|
[1e-06,0.001): 4.7788% +0.7665% 0.000% 0.001% 67026
|
|
[0.001,0.0599): 4.5658% +0.1902% 0.013% 11.063% 12374574
|
|
[0.0599,0.1): 4.6294% +0.1297% 0.027% 10.881% 4486724
|
|
[0.1,0.229): 4.9079% +0.0866% 0.124% 25.365% 5466556
|
|
[0.229,0.769): 6.9340% +0.0100% 0.301% 24.638% 2239488
|
|
[0.769,4.62): 11.4421% -0.0990% 0.615% 10.315% 223948
|
|
[4.62,inf): 10.4475% -0.1789% 98.921% 17.738% 24884
|
|
|
|
===== 2mass_galactic_center_flat_4k_50deg_1e13_beta3-fast-4_HDR.fits ===== relative_L2=4.3725%
|
|
top |d| RGB samples: sq-error energy base energy linear-RGB sum sample share
|
|
top 0.0010%: 65.911% 35.557% 2.418% 0.0010%
|
|
top 0.0100%: 94.540% 86.397% 8.879% 0.0100%
|
|
top 0.1000%: 99.108% 96.708% 16.179% 0.1000%
|
|
top 1.0000%: 99.848% 99.208% 25.909% 1.0000%
|
|
top 10.0000%: 99.982% 99.694% 45.966% 10.0000%
|
|
base-value range (disjoint): rel_RMS signed bias base energy % linear-RGB sum % samples
|
|
[1e-06,0.001): 2.4187% +0.5689% 0.000% 0.001% 67026
|
|
[0.001,0.0599): 2.2772% +0.0729% 0.013% 11.063% 12374574
|
|
[0.0599,0.1): 2.3129% +0.0550% 0.027% 10.881% 4486724
|
|
[0.1,0.229): 2.4542% +0.0393% 0.124% 25.365% 5466556
|
|
[0.229,0.769): 3.4700% +0.0166% 0.301% 24.638% 2239488
|
|
[0.769,4.62): 5.6752% -0.0189% 0.615% 10.315% 223948
|
|
[4.62,inf): 4.3682% -0.0469% 98.921% 17.738% 24884
|
|
```
|
|
|
|
The FITS RGB channels are flattened into scalar samples: `sq-error energy` is
|
|
the fraction of `||fast-base||^2`, `linear-RGB sum` is the sum of baseline
|
|
linear-RGB sample values (proportional to total flux, not a per-source
|
|
photometry), and the base-value ranges partition all samples and sum to 100%.
|
|
|
|
The top 0.01% of RGB channel samples account for 95.7% (`N=2`) or 94.5%
|
|
(`N=4`) of squared-error energy and about 9% of the baseline linear-RGB sum.
|
|
The flux-bearing faint ranges (`[1e-3,0.0599)`, `[0.0599,0.1)`, `[0.1,0.229)`,
|
|
together ~47% of the linear-RGB sum) have 2.3-4.9% local relative RMS and
|
|
signed bias of `+0.04%` to `+0.19%`; the many faint PSFs partially cancel. This
|
|
is consistent with the concentrated bright-core difference being predominantly a
|
|
bounded sub-pixel redistribution rather than a large net linear-RGB loss, and
|
|
explains why this tone-mapped still PNG remains smooth despite the global
|
|
relative L2.
|
|
|
|
This comparison contains one independent frame only. It does not measure
|
|
temporal coherence: nearest deposition jumps by `1/N` output pixel per axis
|
|
when a moving image crosses a supersampled-cell boundary (`0.5 px` at `N=2`,
|
|
`0.25 px` at `N=4`). Both can produce visible movie flicker and are not
|
|
qualified here as visually faithful movie-output paths.
|
|
|
|
## Reading
|
|
|
|
- Steady-state FFTW is ~109x (N=2) and ~279x (N=4) faster than the spatial
|
|
reference at 320x240, and stays under ~0.06 s per frame at 960x540.
|
|
- 4K N=2 resolves in ~2.5 s (ESTIMATE) or ~0.52 s (MEASURE) on this host; 4K N=4
|
|
needs ~7.6 GiB scratch and ~3.3 s (ESTIMATE).
|
|
- FFTW-versus-spatial differences are floating-point roundoff (`max_abs` at the
|
|
`1e-15` level against peaks near `0.5`), not crop, wrap, channel, or
|
|
normalization errors.
|
|
- At the committed revision, the production-density 4K Galactic-center run
|
|
completes in 15.439 s at N=2 versus 68.610 s for the standard path (4.444x
|
|
end-to-end), with identical catalog image/deposit/filter counts. N=4 trades
|
|
26.1% more wall time for materially lower spatial error.
|
|
- The 4K still-frame error is concentrated: the top 0.01% of RGB channel
|
|
samples hold ~95% of the squared-error energy but only ~9% of the baseline
|
|
linear-RGB sum, while the flux-bearing faint-value ranges stay at ~2-5% local
|
|
relative RMS with signed bias at or below ~0.2%. This does not establish
|
|
temporal fidelity.
|