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https://github.com/storytold/photocraft.git
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Rene Leonhardt
aa715535f3
Move cached keys and compressed buffers between saves, and compare weak allocation pointers without temporary strong-reference updates. Keep payload budgets and archive bytes unchanged. Allow fallible tile edits after a cached save. Move pixel storage when only weak references remain; use a fallible copy for shared storage and restore the original tile if the copy fails. Cover cache key reuse, edits after saves at every depth, and weak/shared tile ownership. Name the fixed revisions behind the existing timings.
48 lines
3.2 KiB
Markdown
48 lines
3.2 KiB
Markdown
# Native save writer reuse
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Each open document keeps a writer through the ordinary save settings. Unchanged tile and
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blob identities reuse weakly cached hashes; compressed payload capacity retained between
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saves is capped at 64 MiB. The last cache owner releases it. Other formats ignore the cache,
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and one-shot exports still work. Save As names, previews, cancellation, atomic writes and
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saved revisions keep their existing behavior. Tile hash identity includes sample depth.
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Fallible edits move uniquely owned tile pixels when weak cache references remain; shared
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pixels keep their copy-on-write behavior.
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The format writer's compressed-cache limit defaults to unbounded for existing callers.
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The UI selects 64 MiB. This is retained memory that a one-shot save would release; it does
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not cap current-save scratch or ZIP output, and it does not reduce bytes written to disk.
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## Measurements
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Release build on Apple M4 Max. CC0 Pixls foliage (24 MP, unscaled crop) and city (12 MP,
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native size) edits contain a photograph, global Levels, Curves and masked foreground Levels.
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ProPhoto RGB is retained. U8/U16/F32 are tested; F32 derives from developed U16 samples.
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Two upstream PSD designs add authored layered-file coverage. No generated noise is timed.
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The table uses seven alternating pairs after warmup and includes thumbnail/composite
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rendering, encoding, APFS atomic writes, fsync and rename. Hashing, reload equality and file
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removal are outside timers. Intervals are paired bootstrap 95% descriptions of these samples.
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These writer-reuse results compare main `d95fdf31` and the original parent `f64a143c`
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with `05bd004b`; the original parent's production save path matches that main baseline.
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Each small edit changes one real-photo tile. The later cache-ownership changes remove
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redundant allocations and reference-count updates; no separate timing gain is claimed.
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| Document | Operation | Main ms | Original parent ms | Writer reuse ms | Change vs original parent |
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|---|---|---:|---:|---:|---:|
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| 24 MP foliage, U16 | save-first-disk | 966.0 | 966.0 | 984.9 | +2.0% (-8.5..+2.7) |
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| 24 MP foliage, U16 | save-repeat-disk | 983.0 | 983.0 | 651.8 | -33.7% (-35.8..-30.9) |
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| 24 MP foliage, U16 | save-edit-disk | 968.6 | 968.6 | 640.1 | -33.9% (-34.2..-33.0) |
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| 12 MP city, U8 | save-first-disk | 660.8 | 660.8 | 621.6 | -5.9% (-7.5..+1.1) |
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| 12 MP city, U8 | save-repeat-disk | 658.9 | 658.9 | 496.6 | -24.6% (-26.4..-18.8) |
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| 12 MP city, U8 | save-edit-disk | 628.4 | 628.4 | 502.2 | -20.1% (-26.3..-17.8) |
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An independent nine-pair U16 first-save check changed its median delta from +2.0% to -5.9%,
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with both intervals crossing zero; no repeatable first-save regression or speedup is established.
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Initial in-memory repeated-export medians across six photo/depth cases improve 18–47%.
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The independent disk runs confirm 20–34% gains for repeated and small-edit saves.
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Peak RSS is close to main; the retained-payload idle-memory cost still applies.
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Every output is byte-identical to the baseline and reloads to the complete source document.
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Scoped tests cover cache capacity/output, weak identities, sample depth, Save As, lifetime and
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save-settings forwarding. Existing save-identity tests cover failed encoding/writing and copies.
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