Doc: Record 4K fast-mode accuracy limits and error distribution
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.
This commit is contained in:
wyj committed
1 parent
229f50cd86
commit
e4d093a9fe
5 files changed
+400
-8
No files matched your search
@@ -132,10 +132,12 @@ PNGs. The command above omits the optional HDR and lens-map exports.
|
|||||||
This example infers a position facing the hole from its look direction and radius. Adaptive refinement should
|
This example infers a position facing the hole from its look direction and radius. Adaptive refinement should
|
||||||
be configured for the desired image accuracy; it is disabled by default.
|
be configured for the desired image accuracy; it is disabled by default.
|
||||||
Camera controls, movie sequences, lens-map reuse, PSF settings, and HDR output
|
Camera controls, movie sequences, lens-map reuse, PSF settings, and HDR output
|
||||||
are described in [usage.md](usage.md). For fast previews, `--fast-mode` replaces
|
are described in [usage.md](usage.md). For fast single-frame previews,
|
||||||
per-event PSF splats with a supersampled delta deposit plus one global PSF
|
`--fast-mode` replaces per-event PSF splats with a supersampled delta deposit
|
||||||
convolution and downsample. Both binaries provide a complete option list with
|
plus one global PSF convolution and downsample. Its nearest-deposit path is not
|
||||||
`--help`.
|
qualified for temporally coherent movie output; see [usage.md](usage.md) for
|
||||||
|
the spatial and temporal accuracy limits. Both binaries provide a complete
|
||||||
|
option list with `--help`.
|
||||||
|
|
||||||
### Example: Looking outward just above the Schwarzschild horizon
|
### Example: Looking outward just above the Schwarzschild horizon
|
||||||
|
|
||||||
|
|||||||
@@ -5,6 +5,10 @@ convolution. This record separates one-time plan/setup from steady-state
|
|||||||
execution and repeats the bounded Galactic-center comparison. Raw resolver and
|
execution and repeats the bounded Galactic-center comparison. Raw resolver and
|
||||||
end-to-end output is pasted verbatim from the runs below.
|
end-to-end output is pasted verbatim from the runs below.
|
||||||
|
|
||||||
|
The later production-density 4K comparison is recorded separately against the
|
||||||
|
first committed FFTW implementation, revision
|
||||||
|
`229f50cd864d9768324042c10edbb56bfc120f08`.
|
||||||
|
|
||||||
## Environment
|
## Environment
|
||||||
|
|
||||||
- Git revision: `3deebfb` plus the uncommitted FFTW work.
|
- Git revision: `3deebfb` plus the uncommitted FFTW work.
|
||||||
@@ -269,6 +273,222 @@ fast_n2.png 1f144aefb4a5520d9d76a13ab69026a72580663e5e45f53128a87a0801176ccf
|
|||||||
fast_n4.png 679f14a67a085f76c144ecbe36af51b3b2534c152e8ef59708a7884a3f7c8464
|
fast_n4.png 679f14a67a085f76c144ecbe36af51b3b2534c152e8ef59708a7884a3f7c8464
|
||||||
```
|
```
|
||||||
|
|
||||||
|
## Production-density 4K Galactic-center comparison
|
||||||
|
|
||||||
|
This is the full 3840x2160, 50-degree-field run over the local processed 2MASS
|
||||||
|
all-sky catalog, not the bounded 320x240 comparison above.
|
||||||
|
|
||||||
|
### Provenance
|
||||||
|
|
||||||
|
- Git revision: `229f50cd864d9768324042c10edbb56bfc120f08`
|
||||||
|
(`Feat: Use FFTW linear convolution for CPU fast-mode PSF resolve`).
|
||||||
|
- The tracked worktree matched that revision when this record was written; the
|
||||||
|
unrelated untracked `nmesh_spacetime_output_format.md` was not an input.
|
||||||
|
- Executable: `build/Release/minkowski_sky`, built at
|
||||||
|
`2026-09-25 23:16:45 -0400`, before the three runs below; size 146,856 bytes;
|
||||||
|
SHA-256
|
||||||
|
`7f6486285b2ff498adb2d4f1acaf62dc96b11125c9cec114f572b9379648962c`.
|
||||||
|
A Make dry-run after the commit requested only the Makefile's unconditional
|
||||||
|
`FORCE` relink and no object recompilation, so the recorded binary used the
|
||||||
|
object set corresponding to the committed tracked sources.
|
||||||
|
- Host: 12th Gen Intel Core i7-12700K, 16 hardware threads, 128 GB. The commands
|
||||||
|
did not explicitly set `OMP_NUM_THREADS`; fast-mode initialization reported
|
||||||
|
`workers=16`.
|
||||||
|
- Input: `assets/2mass/processed/all_sky`, observed when recording as 64,801
|
||||||
|
regular files and 16,207,861,727 bytes. The renderer selected 1,742 tiles and
|
||||||
|
loaded 54,509,992 stars in each run. No content manifest hash was recorded for
|
||||||
|
this external processed catalog.
|
||||||
|
- Timing: zsh built-in `time`; its final timing line is included verbatim for
|
||||||
|
each command.
|
||||||
|
|
||||||
|
### Standard cached spatial PSF
|
||||||
|
|
||||||
|
```sh
|
||||||
|
time ./build/Release/minkowski_sky \
|
||||||
|
--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-base.png
|
||||||
|
```
|
||||||
|
|
||||||
|
```text
|
||||||
|
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
|
||||||
|
Blackbody backend: lut
|
||||||
|
PSF cache ready: 64x64 phases, radius 85 px, relative tail 1e-06, tail abs 1e-06, boundary 1e-07, build 2.176 s
|
||||||
|
Catalog prefetch: 1742 requested, 1742 newly loaded (54509992 stars), 0 unavailable in 5.886 s; 4 loader workers
|
||||||
|
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
|
## Reading
|
||||||
|
|
||||||
- Steady-state FFTW is ~109x (N=2) and ~279x (N=4) faster than the spatial
|
- Steady-state FFTW is ~109x (N=2) and ~279x (N=4) faster than the spatial
|
||||||
@@ -278,3 +498,12 @@ fast_n4.png 679f14a67a085f76c144ecbe36af51b3b2534c152e8ef59708a7884a3f7c8464
|
|||||||
- FFTW-versus-spatial differences are floating-point roundoff (`max_abs` at the
|
- 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
|
`1e-15` level against peaks near `0.5`), not crop, wrap, channel, or
|
||||||
normalization errors.
|
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.
|
||||||
@@ -859,6 +859,32 @@ C2R，以及在 `(R,R)` 处的裁剪、`1/(Pwidth·Pheight)` 与 `1/N²` 归一
|
|||||||
依赖与 plan 模式取舍见 `build.md` 与
|
依赖与 plan 模式取舍见 `build.md` 与
|
||||||
[`benchmarks/fast_mode_fftw_2026-09-25.md`](benchmarks/fast_mode_fftw_2026-09-25.md)。
|
[`benchmarks/fast_mode_fftw_2026-09-25.md`](benchmarks/fast_mode_fftw_2026-09-25.md)。
|
||||||
|
|
||||||
|
fast mode 的单星精度由 deposit 模式与 `N` 决定：`nearest` 的格点间距是
|
||||||
|
每轴 `1/N` 个输出像素，单帧瞬时舍入误差至多是 `1/(2N)`；在
|
||||||
|
`--psf-fwhm-pixels` 不变时它与图像分辨率无关，只有增大 `N`（或使用保持
|
||||||
|
质心、但会展宽 profile 的 `bilinear`）才会降低。
|
||||||
|
|
||||||
|
但单星偏移不等于一张稠密静态图的整图误差。生产密度 4K 银心单帧对照实测
|
||||||
|
fast 对标准路径的 HDR relative L2 为 `N=2` 时 `10.44%`、`N=4` 时 `4.37%`，
|
||||||
|
线性 RGB 总和偏差 `+0.018%`。把 FITS 三通道展平后，按 `|fast-base|` 排序
|
||||||
|
的前 `0.01%` RGB channel samples 占平方误差能量的 `95.7%`（`N=2`）或
|
||||||
|
`94.5%`（`N=4`），其 baseline linear-RGB 总和约占 `9%`。不重叠的 base-value
|
||||||
|
分区中，承载 flux 的暗值区间（`[1e-3,0.06)`、`[0.06,0.1)`、`[0.1,0.23)`，
|
||||||
|
合计约 `47%` 的 linear-RGB 总和）给出约 `2-5%` local relative RMS 与不高于
|
||||||
|
`0.19%` 的 signed bias。这一分布与大量暗星 PSF 的位置误差部分相消、已分辨
|
||||||
|
亮星核心保留亚像素位移的解释一致。因此只能说这次高密度 4K 单帧的银河纹理
|
||||||
|
明显好于全局 L2 数字所暗示，不能据此外推时间连续性或逐像素精度。
|
||||||
|
|
||||||
|
对 movie，平滑移动的星像跨越 nearest 格点边界时会跳变完整的 `1/N` 输出
|
||||||
|
像素：`N=2` 每轴 `0.5 px`、`N=4` 每轴 `0.25 px`。即使在 4K，这种不连续
|
||||||
|
跳变也可能形成可见闪烁，因此 nearest fast mode 尚未获得保持视频视觉特征的
|
||||||
|
资格。`bilinear` 可消除这一质心跳变，但存在上述 profile 展宽，也尚未作为
|
||||||
|
最终 movie 路径验收。定位上仍是近似路径：对单帧稠密星场，`N=2` 是吞吐
|
||||||
|
默认、`N=4` 是更高保真预览；per-event 参考 PSF 路径仍是定量与 movie 基准。
|
||||||
|
单帧误差分解可用
|
||||||
|
[`scripts/fast_mode_error_decomposition.py`](scripts/fast_mode_error_decomposition.py)
|
||||||
|
复现。
|
||||||
|
|
||||||
PSF 第一版可用 Gaussian；
|
PSF 第一版可用 Gaussian；
|
||||||
以后可换成 Airy 或其他相机模型。
|
以后可换成 Airy 或其他相机模型。
|
||||||
|
|
||||||
|
|||||||
@@ -0,0 +1,98 @@
|
|||||||
|
#!/usr/bin/env python3
|
||||||
|
"""Decompose fast-mode-versus-standard HDR error by scalar RGB sample value.
|
||||||
|
|
||||||
|
The unweighted whole-image relative L2 is dominated by a small number of very
|
||||||
|
bright PSF cores, so it is not a good proxy for how the dense faint-star
|
||||||
|
texture is reproduced. FITS RGB channels are flattened into scalar samples.
|
||||||
|
This tool reports, for each fast-mode FITS image:
|
||||||
|
|
||||||
|
* the cumulative fraction of ||fast-base||^2 contributed by the largest |d|
|
||||||
|
RGB channel samples, alongside their share of the baseline linear-RGB sum;
|
||||||
|
* local relative RMS, signed bias, and share of base energy and linear-RGB
|
||||||
|
sum for a disjoint partition of base-value ranges.
|
||||||
|
|
||||||
|
Usage:
|
||||||
|
python3 scripts/fast_mode_error_decomposition.py BASE.fits FAST.fits [...]
|
||||||
|
"""
|
||||||
|
import sys
|
||||||
|
|
||||||
|
import numpy as np
|
||||||
|
|
||||||
|
|
||||||
|
def read_primary_fits(path):
|
||||||
|
with open(path, 'rb') as stream:
|
||||||
|
header = b''
|
||||||
|
while True:
|
||||||
|
block = stream.read(2880)
|
||||||
|
if not block:
|
||||||
|
raise ValueError(f'{path}: truncated FITS header')
|
||||||
|
header += block
|
||||||
|
if any(block[i:i + 8] == b'END ' for i in range(0, 2880, 80)):
|
||||||
|
break
|
||||||
|
cards = {}
|
||||||
|
for i in range(0, len(header), 80):
|
||||||
|
card = header[i:i + 80].decode('ascii', 'replace')
|
||||||
|
key = card[:8].strip()
|
||||||
|
if key in ('NAXIS1', 'NAXIS2', 'NAXIS3', 'BITPIX', 'NAXIS'):
|
||||||
|
cards[key] = int(card[10:30])
|
||||||
|
if key == 'END':
|
||||||
|
break
|
||||||
|
stream.seek(len(header))
|
||||||
|
count = cards['NAXIS1'] * cards.get('NAXIS2', 1) * cards.get('NAXIS3', 1)
|
||||||
|
dtype = '>f4' if cards['BITPIX'] == -32 else '>f8'
|
||||||
|
return np.frombuffer(stream.read(count * np.dtype(dtype).itemsize),
|
||||||
|
dtype=dtype).astype(np.float64)
|
||||||
|
|
||||||
|
|
||||||
|
def decompose(name, base, fast, ranks=(1e-5, 1e-4, 1e-3, 1e-2, 1e-1)):
|
||||||
|
diff = fast - base
|
||||||
|
abs_diff = np.abs(diff)
|
||||||
|
base_l2_sq = float(np.dot(base, base))
|
||||||
|
diff_l2_sq = float(np.dot(abs_diff, abs_diff))
|
||||||
|
base_rgb_sum = float(base.sum())
|
||||||
|
print(f'\n===== {name} ===== relative_L2={np.sqrt(diff_l2_sq / base_l2_sq) * 100:.4f}%')
|
||||||
|
order = np.argsort(abs_diff)[::-1]
|
||||||
|
print('top |d| RGB samples: sq-error energy base energy linear-RGB sum sample share')
|
||||||
|
for frac in ranks:
|
||||||
|
k = max(1, int(frac * base.size))
|
||||||
|
idx = order[:k]
|
||||||
|
print(f' top {frac * 100:8.4f}%: {np.dot(abs_diff[idx], abs_diff[idx]) / diff_l2_sq * 100:7.3f}%'
|
||||||
|
f' {np.dot(base[idx], base[idx]) / base_l2_sq * 100:9.3f}%'
|
||||||
|
f' {base[idx].sum() / base_rgb_sum * 100:8.3f}%'
|
||||||
|
f' {k / base.size * 100:9.4f}%')
|
||||||
|
nonzero = base[base > 0]
|
||||||
|
quantiles = np.quantile(nonzero, [0.5, 0.9, 0.99, 0.999])
|
||||||
|
edges = np.unique(np.concatenate(
|
||||||
|
([-np.inf, 1e-6, 1e-3, 1e-1], quantiles, [np.inf])))
|
||||||
|
print('base-value range (disjoint):'
|
||||||
|
' rel_RMS signed bias base energy % linear-RGB sum % samples')
|
||||||
|
for low, high in zip(edges[:-1], edges[1:]):
|
||||||
|
mask = (base > low) & (base <= high)
|
||||||
|
if not mask.any():
|
||||||
|
continue
|
||||||
|
bin_diff = diff[mask]
|
||||||
|
bin_base = base[mask]
|
||||||
|
rel = np.sqrt(np.dot(bin_diff, bin_diff) / np.dot(bin_base, bin_base))
|
||||||
|
bias = bin_diff.sum() / bin_base.sum()
|
||||||
|
lo = '-inf' if low == -np.inf else f'{low:.3g}'
|
||||||
|
hi = 'inf' if high == np.inf else f'{high:.3g}'
|
||||||
|
print(f' [{lo},{hi}): {rel * 100:9.4f}% {bias * 100:+10.4f}%'
|
||||||
|
f' {np.dot(bin_base, bin_base) / base_l2_sq * 100:8.3f}%'
|
||||||
|
f' {bin_base.sum() / base_rgb_sum * 100:7.3f}% {int(mask.sum())}')
|
||||||
|
|
||||||
|
|
||||||
|
def main(argv):
|
||||||
|
if len(argv) < 3:
|
||||||
|
print(__doc__)
|
||||||
|
return 2
|
||||||
|
base = read_primary_fits(argv[1])
|
||||||
|
for path in argv[2:]:
|
||||||
|
fast = read_primary_fits(path)
|
||||||
|
if fast.shape != base.shape:
|
||||||
|
raise ValueError(f'{path}: shape {fast.shape} != base {base.shape}')
|
||||||
|
decompose(path.rsplit('/', 1)[-1], base, fast)
|
||||||
|
return 0
|
||||||
|
|
||||||
|
|
||||||
|
if __name__ == '__main__':
|
||||||
|
sys.exit(main(sys.argv))
|
||||||
@@ -278,11 +278,12 @@ supersampled scale, so the requested FWHM and beta are preserved by the
|
|||||||
downsample itself.
|
downsample itself.
|
||||||
|
|
||||||
`--fast-deposit nearest` (default) deposits into the single nearest
|
`--fast-deposit nearest` (default) deposits into the single nearest
|
||||||
supersampled pixel. It keeps the PSF shape exactly but quantizes the image
|
supersampled pixel. It keeps the PSF shape exactly on that grid. The grid
|
||||||
position to `1/(2N)` output pixels. `--fast-deposit bilinear` deposits into 4
|
spacing is `1/N` output pixel per axis, while the instantaneous rounding error
|
||||||
|
is bounded by `1/(2N)` per axis. `--fast-deposit bilinear` deposits into 4
|
||||||
adjacent pixels; it preserves the continuous centroid but broadens the profile
|
adjacent pixels; it preserves the continuous centroid but broadens the profile
|
||||||
(measured +4.5%/+1.9%/+1.0% FWHM at N=2/3/4). The deposition experiment and its
|
(measured +4.5%/+1.9%/+1.0% FWHM at N=2/3/4). The deposition experiment and
|
||||||
raw output are in
|
its raw output are in
|
||||||
[benchmarks/fast_mode_deposit_2026-09-18.md](benchmarks/fast_mode_deposit_2026-09-18.md).
|
[benchmarks/fast_mode_deposit_2026-09-18.md](benchmarks/fast_mode_deposit_2026-09-18.md).
|
||||||
|
|
||||||
Fast mode is available only in the CPU PSF backend. It ignores
|
Fast mode is available only in the CPU PSF backend. It ignores
|
||||||
@@ -291,6 +292,42 @@ bright event whose requested support exceeds that radius is wing-clipped and
|
|||||||
counted in the report. `--psf-min-y` is still applied per event. Fast mode is a
|
counted in the report. `--psf-min-y` is still applied per event. Fast mode is a
|
||||||
preview approximation, not the physically exact per-event PSF path.
|
preview approximation, not the physically exact per-event PSF path.
|
||||||
|
|
||||||
|
Its accuracy is governed by the deposit mode and `N`, not by the output
|
||||||
|
resolution. A nearest deposit shifts each image by at most `1/(2N)` output
|
||||||
|
pixels per axis. The separate two-dimensional centroid-distance experiment
|
||||||
|
measured worst cases of ~`0.30 px` at `N=2` and ~`0.12 px` at `N=4` for a FWHM
|
||||||
|
`2.7`, beta `4.5` PSF. These offsets remain fixed fractions of one output
|
||||||
|
pixel: with `--psf-fwhm-pixels` held fixed, a larger image does not reduce
|
||||||
|
them, and only a larger `N` (or the centroid-preserving bilinear deposit, at
|
||||||
|
the cost of a broadened profile) does.
|
||||||
|
|
||||||
|
That per-star number is not how one dense still image behaves. In the measured
|
||||||
|
production-density 4K Galactic-center frame, fast-versus-standard HDR relative
|
||||||
|
L2 is `10.44%` at `N=2` and `4.37%` at `N=4`, with a `+0.018%` total
|
||||||
|
linear-RGB-sum offset. The difference is concentrated in a small set of scalar
|
||||||
|
RGB channel samples: the top `0.01%` ranked by `|fast-base|` account for
|
||||||
|
`95.7%` (`N=2`) or `94.5%` (`N=4`) of squared-error energy, while containing
|
||||||
|
about `9%` of the summed baseline linear-RGB values. The disjoint base-value
|
||||||
|
partition puts the flux-bearing faint ranges (`[1e-3,0.06)`, `[0.06,0.1)`,
|
||||||
|
`[0.1,0.23)`, together ~`47%` of the linear-RGB sum) at ~`2-5%` local relative
|
||||||
|
RMS with signed bias at or below `0.19%`. This pattern is consistent with
|
||||||
|
partial cancellation among many faint PSFs, while resolved bright cores retain
|
||||||
|
bounded sub-pixel displacement. It does not make fast mode pixelwise or
|
||||||
|
visually lossless.
|
||||||
|
|
||||||
|
These measurements characterize independent still frames only. With nearest
|
||||||
|
deposition, a smoothly moving image jumps by one complete grid spacing when it
|
||||||
|
crosses a cell boundary: `1/N` output pixel per axis, or `0.5 px` at `N=2` and
|
||||||
|
`0.25 px` at `N=4`. Such discontinuities can appear as visible flicker even at
|
||||||
|
4K. Neither nearest mode is therefore qualified as a temporally coherent movie
|
||||||
|
output path. Bilinear deposition removes this particular centroid jump but has
|
||||||
|
the profile-broadening tradeoff above and has not been qualified as a final
|
||||||
|
movie path either. For single-frame dense-star previews, `N=2` remains the
|
||||||
|
throughput default and `N=4` the higher-fidelity point; the exact per-event
|
||||||
|
reference PSF path remains the quantitative and movie reference. The
|
||||||
|
single-frame error decomposition is reproducible with
|
||||||
|
[`scripts/fast_mode_error_decomposition.py`](scripts/fast_mode_error_decomposition.py).
|
||||||
|
|
||||||
In CPU builds the global convolution is a zero-padded FFTW linear convolution
|
In CPU builds the global convolution is a zero-padded FFTW linear convolution
|
||||||
(`fftw3`/`fftw3_omp`, double precision). The immutable kernel spectrum, FFTW
|
(`fftw3`/`fftw3_omp`, double precision). The immutable kernel spectrum, FFTW
|
||||||
plans, and scratch buffers are built once when the accumulator is initialized
|
plans, and scratch buffers are built once when the accumulator is initialized
|
||||||
|
|||||||
Reference in new issue
Block a user