a092ee34aa260422b6d38b08c008d98556768bce
27 Commits
| Author | SHA1 | Message | Date | |
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 marfrit
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a092ee34aa |
Merge pull request 'QPU is default substrate: recipe table + ctx env-var override' (#7) from noether/qpu-default-recipe-cycles-5-8 into main
Reviewed-on: #7 |
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 claude-noether
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74687d9def |
cycle 7: V3D shader for H.264 IDCT 8x8
Mirrors cycle 6 (PR #7 prior commit) but at 8x8 scale: 8 lanes per
block, 8 blocks per WG. H.264 §8.5.13.2 1D butterfly twice (row
pass, column pass), (val + 32) >> 6 rounded + clipped + added to
dst.
Bit-exact first try on hertz (Pi 5, V3D 7.1):
H264_IDCT4 recipe substrate: 2 (QPU)
H264_IDCT8 recipe substrate: 2 (QPU) ← flipped
H264_DEBLOCK_LV recipe substrate: 2 (QPU)
H264_QPEL_MC20 recipe substrate: 1 (CPU) ← task #165 remaining
H.264 IDCT 4x4: 2048/2048 bytes bit-exact
H.264 IDCT 8x8: 2048/2048 bytes bit-exact ← QPU
H.264 deblock luma v: 2048/2048 bytes bit-exact
H.264 qpel mc20: 1024/1024 bytes bit-exact
8 of 9 daedalus-fourier cycles now QPU-by-recipe. Only cycle 9
(H.264 luma qpel mc20) still CPU — different shape (6-tap MC
filter, not a transform) so needs its own shader template; task
#165 covers it as a follow-on.
Same pattern as cycle 6 commit (
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claude-noether
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65bd5c3fe3 |
cycle 6: V3D shader for H.264 IDCT 4x4 (first cycle-6 QPU dispatch)
Per the QPU-default substrate decree 2026-05-23, cycle 6 (H.264
IDCT 4x4 + add) was the highest-priority H.264 kernel to flip
from NEON-only to QPU-capable. The same shape as VP9 IDCT 8x8
(cycle 1) — two-pass butterfly with shared-memory transpose —
but at 4x4 scale: 4 lanes per block, 16 blocks per WG.
What's added:
- src/v3d_h264_idct4.comp: GLSL compute shader implementing
the H.264 §8.5.12.1 1D butterfly twice (row pass then column
pass), with (val + 32) >> 6 rounding and clip-to-u8 add to
dst. Block memory layout is column-major (matches FFmpeg
`ff_h264_idct_add_neon` convention).
- CMakeLists: glslang rule + install entry for v3d_h264_idct4.spv.
- dispatch_h264_idct4_qpu() in daedalus_core.c: lazy pipeline
init, 3 SSBOs (coeffs / dst / meta as uvec4), push-constant
(n_blocks, dst_stride), 16 blocks per WG dispatch. Matches
the existing dispatch_*_qpu patterns; uses
v3d_runner_create_buffer / destroy_buffer (will swap to
pool API once PR #6 lands).
- daedalus_dispatch_h264_idct4() replaces ROUTE_CPU_ONLY with
the same CPU/QPU substrate switch the deblock dispatch uses.
- daedalus_recipe_substrate_for(H264_IDCT4) returns QPU now
that the shader exists.
Verification on hertz (Pi 5 + V3D 7.1):
$ ./test_api_h264
=== Phase 8a API smoke: H.264 kernels via recipe dispatch ===
H264_IDCT4 recipe substrate: 2 (1=CPU, 2=QPU)
H264_IDCT8 recipe substrate: 1
H264_DEBLOCK_LV recipe substrate: 2
H264_QPEL_MC20 recipe substrate: 1
H.264 IDCT 4x4: 2048/2048 bytes bit-exact (100.0000%) ← QPU
H.264 IDCT 8x8: 2048/2048 bytes bit-exact
H.264 deblock luma v: 2048/2048 bytes bit-exact
H.264 qpel mc20: 1024/1024 bytes bit-exact
The AUTO-substrate path now picks QPU for H.264 IDCT 4x4, and
the output is bit-exact against the C reference (which is
identical to the NEON .S code by construction — same FFmpeg
upstream).
Remaining cycle-6/7/9 work in task #165:
- cycle 7: H.264 IDCT 8x8 (template same shape; 8 lanes per
block, fewer blocks per WG)
- cycle 9: H.264 luma qpel mc20 (different shape — 6-tap MC
not a transform)
This commit lands the cycle-6 piece of task #165.
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claude-noether
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0a042a8e95 |
v3d_runner: buffer pool for QPU dispatch hot path
Per the QPU-default substrate decree 2026-05-23: the per-dispatch
vkAllocateMemory in dispatch_*_qpu was the biggest single fixable
contributor to QPU dispatch overhead. This pools v3d_buffer
allocations by power-of-2 size class so the second-and-subsequent
dispatch hits a freelist instead of paying ~10-50us of Mesa-V3D7
memory-allocation cost per call.
API additions (v3d_runner.h):
- v3d_runner_acquire_buffer(): pulls from per-bucket freelist;
falls through to v3d_runner_create_buffer() on miss.
- v3d_runner_release_buffer(): pushes back onto the freelist; the
backing VkBuffer/VkDeviceMemory only get vkFreeMemory'd in
v3d_runner_destroy().
- v3d_runner_pool_total_bytes(): diagnostic watermark.
Size classes 2^8..2^23 (256 B to 8 MiB). Oversize requests fall
through to non-pooled (vkAllocateMemory) for both ends — pool stays
correct, just degenerates to old behaviour for those calls.
Migration: daedalus_core.c dispatch_*_qpu paths globally swap
create_buffer → acquire_buffer and destroy_buffer → release_buffer.
All five QPU dispatch functions (idct8 / lpf / mc_8h / cdef /
h264_deblock) now reuse buffers across calls. test_api_idct stays
bit-exact (4096/4096 bytes on CPU/QPU/AUTO substrates on hertz).
Microbench (tests/bench_pool_overhead.c) on hertz (Pi 5,
6.18.29+rpt-rpi-2712, V3D 7.1):
call 0: 434.89 us (cold — 3x vkAllocateMemory)
call 1: 100.06 us (pool hit on all 3 buffers)
steady-state:
p50: 76.44 us
p90: 90.52 us
mean: 77.95 us
first-call / steady-state ratio: 5.7x
The remaining ~76us steady-state is dominated by vkQueueWaitIdle +
shader execution + per-call descriptor-set update + command-buffer
allocation — addressed in follow-on tasks 161 (persistent cmdbuf)
and 162 (dmabuf import for dst, eliminates memcpy in/out).
Refs daedalus-fourier task #160.
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claude-noether
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b3de96b21c |
CMakeLists: make daedalus-fourier.pc relocatable via ${pcfiledir}
The pkg-config file was generated at *configure* time with
`prefix=${CMAKE_INSTALL_PREFIX}`, which captured whatever
CMAKE_INSTALL_PREFIX happened to be set to at `cmake -B build`
time — typically the default `/usr/local`. `cmake --install
build --prefix /foo` then put the files under /foo but the .pc
still pointed pkg-config at /usr/local/include and /usr/local/lib,
which broke downstream consumers configuring against the install
tree.
Concrete bite encountered today on hertz: the daedalus-v4l2 daemon
CMake configure on a /tmp/df-prefix install tree resolved
DAEDALUS_FOURIER_INCLUDE_DIRS to /usr/local/include (empty path on
the test host), so main.c failed to find <daedalus.h>.
Fix: write the .pc with `prefix=${pcfiledir}/<rel>` where <rel> is
the configure-time-computed relative path from
<prefix>/<libdir>/pkgconfig back to <prefix>. pkg-config
substitutes ${pcfiledir} with the actual on-disk location of the
.pc at lookup time, so the resolved prefix tracks wherever the
install tree is moved to — including DESTDIR-staged builds, apt
package installs, and ad-hoc `cmake --install --prefix /tmp/foo`
test installs.
The relative-path computation handles GNUInstallDirs layouts that
add multiarch tuples (Debian's lib/aarch64-linux-gnu) without
hard-coding `../..`. Tested on hertz (Debian trixie, libdir=lib):
prefix=${pcfiledir}/../../
...
$ pkg-config --variable=prefix daedalus-fourier
/tmp/df-prefix-test/lib/pkgconfig/../../
# mv preserves relocation:
$ mv /tmp/df-prefix-test /tmp/df-prefix-moved
$ pkg-config --variable=prefix daedalus-fourier
/tmp/df-prefix-moved/lib/pkgconfig/../../
This unblocks the daedalus-v4l2 daemon out-of-tree builds against
local daedalus-fourier installs and is a prerequisite for tidy
test-rig deployments (per the hertz reload session 2026-05-23).
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claude-noether
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8fdef27a7d |
Phase 8c: H.264 luma qpel mc20 through public API
Extends daedalus-fourier with daedalus_recipe_dispatch_h264_qpel_mc20
so libavcodec.so can route H264QpelContext.put_h264_qpel_pixels_tab[1][2]
through the recipe layer instead of ff_put_h264_qpel8_mc20_neon directly.
API additions (header + library):
- daedalus_h264_qpel_meta { dst_off, src_off }
- daedalus_dispatch_h264_qpel_mc20(ctx, sub, dst, src, stride,
n_blocks, meta)
- daedalus_recipe_dispatch_h264_qpel_mc20(...) (AUTO wrapper)
- DAEDALUS_KERNEL_H264_QPEL_MC20 = 9 in the recipe-query enum
- daedalus_recipe_substrate_for() returns CPU NEON for cycle 9
The 6-tap horizontal half-pel filter signature matches FFmpeg's
H264QpelContext convention exactly: dst and src share a single stride
and src already points at output column 0 (filter reads cols -2..+3).
Single-stride API to make the marfrit-packages FFmpeg shim a
straight pointer-pass; no buffer rearrangement.
Verdict per docs/k9_h264qpel_mc20.md: CPU NEON. Per-block 7.6 ns
gives 135x margin over 30 fps 1080p; QPU dispatch floor at ~250 ns
makes any V3D shader strictly worse. Recipe table reflects that —
the recipe_dispatch entry is a one-line forward to the CPU path.
CMakeLists changes:
- h264qpel_neon.S added to the daedalus_core static lib (only the
bench targets owned it before; now the public API needs it too)
- tests/h264_qpel8_mc20_ref.c added to the test_api_h264 target
Phase 8a/8b smoke gains a 4th case (test_qpel_mc20): 1024/1024
bytes bit-exact via daedalus_recipe_dispatch_h264_qpel_mc20.
Refs reauktion/daedalus-v4l2#11 — substitution arc step 2 cycle 9.
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claude-noether
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47d0107809 |
CMakeLists: install rules + pkg-config for daedalus_core
Make daedalus_core installable so sibling consumers (Phase 8 V4L2
daemon, future libva-v4l2-request-fourier integration tests, etc.)
can `pkg_check_modules(DAEDALUS REQUIRED daedalus-fourier)` against
a system-installed copy.
Installs:
- lib/libdaedalus_core.a
- include/daedalus.h
- lib/pkgconfig/daedalus-fourier.pc
- share/daedalus-fourier/shaders/*.spv (only when
DAEDALUS_BUILD_VULKAN is ON; consumers using
daedalus_ctx_create_no_qpu() don't need them)
pkg-config surfaces the static-archive transitive deps via
Libs.private (-lpthread -ldl -lm) and Requires.private (vulkan),
so a consumer doing `pkg-config --static --libs daedalus-fourier`
gets the full link line. Non-static consumers (using the
no_qpu path) get just `-ldaedalus_core`.
No behaviour change to existing tests / benches.
Verified on hertz (Pi 5, dev host): clean build, all 7 SPIR-V
shaders + the static lib + the header + the .pc file land in
the install prefix.
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marfrit
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5c8b09349c |
Cycle 9 closed: H.264 luma qpel mc20 = 131 Mblock/s NEON, CPU-only
Last unmeasured H.264 kernel. mc20 picked as representative (horizontal half-pel, 6-tap filter; canonical for the H.264 luma qpel family). M1 PASS 10000/10000 first try, M3 = 131.477 Mblock/s on a single core (7.6 ns/block), 135x the 1080p30 floor. Per the cycles 6+7 lightweight-kernel rationale, Phase 4 deferred: QPU dispatch floor (~250 ns/block) is 33x above the NEON per-block cost; R9 ≈ 0.03 deep RED. No realistic QPU offload value. Generalization: all H.264 luma MC variants (mc02, mc11, mc22, etc.) will share this verdict. No need to measure each variant individually. H.264 NEON is dramatically faster than VP9 NEON across the board: - IDCT 4x4: 175 vs N/A (no VP9 analog) - IDCT 8x8: 151 vs 8.2 Mblock/s (18x faster) - MC 6/8-tap: 131 vs 7.0 (19x faster) - Deblock: 92 vs 48 Medge/s (2x faster) H.264 deployment recipe: all CPU NEON except deblock (opportunistic QPU). On a Pi 5 running H.264-only, the QPU is mostly idle. Cycles 1-9 complete. Public API exposes all 9. Next: daedalus-v4l2 sibling repo per locked Phase 8 architecture (B + γ + sibling), then README polish. - external/ffmpeg-snapshot/libavcodec/aarch64/h264qpel_neon.S vendored (1467 lines, all qpel variants) - tests/h264_qpel8_mc20_ref.c: 40-line C ref (clip255 of 6-tap convolution) - tests/bench_neon_h264qpel_mc20.c: M1 + M3 bench - docs/k9_h264qpel_mc20.md: cycle 9 closure with comparison matrix Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
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0a99b16489 |
Phase 8b: opportunistic QPU paths through public API
Wires QPU dispatch for cycles 3 (VP9 MC), 5 (AV1 CDEF), 8 (H.264
deblock) through the public API. These three kernels have recipe
substrate = CPU, but per Issue 003 the mixed-kernel helper value
is real — the dispatch path must exist so override-mode callers
can request QPU on the side.
Pattern mirrors dispatch_idct8_qpu (lazy pipeline + per-call SSBO
alloc + memcpy + dispatch + readback). Each kernel has its own
push-constant struct (mc_pc 3-field, cdef_pc 3-field, deblock_pc
2-field shared with lpf).
Notable bug caught + fixed in test_api_opportunistic_qpu: the
initial dispatch_mc_8h_qpu sized src_max using CPU-side reach
(src_off + 3 + 8 + 7*stride), but the QPU shader reads src[
src_off + row*stride + 0..14] for row=0..7. Last block had 3
uninitialized bytes → 99.8% match → 100% after fix.
After this commit, the public API surface fully covers cycles 1-8:
Cycle 1 (IDCT 8x8): CPU + QPU + AUTO bit-exact
Cycle 2 (LPF wd=4): CPU + QPU + AUTO bit-exact
Cycle 3 (MC 8h): CPU recipe; QPU override bit-exact
Cycle 4 (LPF wd=8): CPU + QPU + AUTO bit-exact
Cycle 5 (CDEF): CPU recipe; QPU override (untested in this
test — bench_v3d_cdef is the authoritative 3-way M1)
Cycle 6 (H.264 IDCT 4x4): CPU only (no QPU shader by recipe)
Cycle 7 (H.264 IDCT 8x8): CPU only
Cycle 8 (H.264 deblock luma-v): CPU recipe; QPU override bit-exact
Tests: test_api_opportunistic_qpu adds CPU-vs-QPU bit-exact
comparison for VP9 MC and H.264 deblock through the API.
test_api_idct, test_api_lpf, test_api_h264 still pass.
Per the locked Phase 8 architecture (project_phase8_architecture
memory): next session opens daedalus-v4l2 sibling repo with
Option B (kernel V4L2 shim + userspace daemon), Option γ (dlopen
FFmpeg parser).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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marfrit
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af8146a2cd |
Phase 8a: H.264 kernels through public API
Extends include/daedalus.h with cycles 6, 7, 8 (H.264 IDCT 4x4, IDCT 8x8, luma deblock luma-v). All recipe-substrate = CPU (matches per-cycle Phase 7 verdicts). src/daedalus_core.c: NEON-path implementations + recipe routing. daedalus_core library now links the full FFmpeg H.264 NEON snapshot (h264idct + h264dsp) plus existing VP9 + dav1d. tests/test_api_h264.c: smoke test covering all 3 H.264 kernels via daedalus_recipe_dispatch_*. All pass 2048/2048 bit-exact. Public API coverage after this commit: - Cycles 1 IDCT 8x8 + 2 LPF4 + 4 LPF8: CPU+QPU+AUTO dispatch (test_api_idct, test_api_lpf, both pass) - Cycle 3 MC 8h: CPU only (QPU dispatch stub returns -1) - Cycle 5 CDEF: CPU only (QPU stub) - Cycle 6 H.264 IDCT 4x4: CPU only (recipe + only NEON wired) - Cycle 7 H.264 IDCT 8x8: CPU only - Cycle 8 H.264 deblock: CPU only (QPU opportunistic — not wired through API yet; bench_v3d_h264deblock exists for direct test) Next Phase 8 sub-step: wire opportunistic QPU dispatch for cycles 3+5+8 through the API (so override-mode users can request QPU). Then surface V4L2-wrapper architecture decisions to user. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
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373f63a910 |
Cycle 8 closed: H.264 deblock R8=0.061 RED, opportunistic helper
Phase 6 deliverable: v3d_h264deblock.comp (132 inst, 4 threads,
no spills). Phase 5 REDs applied:
RED-1: explicit clamp p1'/q1' to [0,255] before uint8 write
RED-2: bench-enforced m.x >= 4*stride contract
M1: 3-way 4096/4096 bit-exact (QPU vs C ref AND vs NEON).
M2: 5.629 Medge/s isolation → R8 = 0.061 RED (predicted 0.09-0.14).
Lower than prediction; H.264 deblock has 4 early-return paths +
2 conditional writes that hurt V3D branchy execution more than
expected.
M4 same-kernel: NEON-3+QPU 12.81 Medge/s ≈ pure-NEON-4 ~12-15
(neutral).
M4 MIXED (real H.264 deployment shape): CPU=MC + QPU=h264deblock
gives CPU MC 25.11 Mblock/s + QPU h264deblock 6.23 Medge/s.
QPU contribution is essentially unchanged from isolation —
the cross-substrate contention is gentle (consistent with
Issue 003's V4 finding).
Verdict: H.264 deblock = opportunistic QPU helper. Same recipe
slot as cycle 5 CDEF. 6 Medge/s helper = 85% of single-NEON-core
deblock capacity, available when CPU is busy with other work.
Cycles 1-8 deployment recipe complete:
Primary QPU: cycles 1+2+4 (VP9 IDCT/LPF, all bandwidth-bound)
Primary CPU: cycles 3+6+7 (compute-heavy or trivially fast on NEON)
Opportunistic helper: cycles 5+8 (CDEF, H.264 deblock)
Phase 9 lessons added:
- Branchy kernels underperform V3D vs straight-line ones
- Mixed-kernel helper value scales with isolation M2, not
same-kernel M4
- R prediction needs branchiness weight, not just compute density
- src/v3d_h264deblock.comp (132 inst QPU shader)
- tests/bench_v3d_h264deblock.c (3-way M1 + M2 + R classification)
- tests/bench_concurrent_mixed.c extended with K_H264DEBLOCK
- CMakeLists.txt: v3d_h264deblock.spv + bench_v3d_h264deblock
+ h264dsp linked into bench_concurrent_mixed
- docs/k8_h264deblock_phase7.md (full closure with cycles 1-8 recipe)
Next: Phase 8 — V4L2 wrapper / deployment infra. Public API
already exposes recipe-default substrate per kernel.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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marfrit
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436a5c4f74 |
Cycle 8 Phase 3 closed: H.264 deblock NEON = 92 Medge/s
M1: 10000/10000 bit-exact (after orientation fix: ff_h264_v_loop_ filter is "vertical filtering of horizontal edges", not "vertical edge"; 16 columns process the edge horizontally with 8 rows of vertical context). M3: 91.947 Medge/s per core. Per-edge 10.9 ns. 11x worst-case 1080p30 floor, 30x realistic floor. Filter triggers on 25 % of edges (random alpha/beta/tc0 covers both gating paths). Cycle 8 Phase 9 lesson: H.264/FFmpeg "v_loop_filter" naming uses filter DIRECTION (vertical) not edge orientation. Edge is horizontal; filter operates vertically across it. Distinct from cycle 6's column-major-block lesson but related discovery pattern. Encoded for future cycles. R8 prediction revised: 0.09-0.14 ORANGE (down from Phase 1's 0.3-0.8 estimate). H.264 deblock is 2x faster on NEON than VP9 LPF wd=4 (cycle 2) but H.264 deblock has more per-edge branches that hurt QPU more. Worth building anyway: - ORANGE in cycle 1's "M4 may rescue" band - Mixed-kernel deployment helper value (Issue 003) matters more than isolation R - 25%-trigger rate gives 4x effective contribution multiplier on QPU side - tests/h264_deblock_ref.c (column-walking C ref per row segment) - tests/bench_neon_h264deblock.c (M1 + M3 bench) - CMakeLists.txt: cycle 8 NEON bench wiring + h264dsp_neon.S - docs/k8_h264deblock_phase3.md (closure) Next: Phase 4 plan QPU shader, Phase 5 Sonnet review. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
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db2205d0e3 |
Cycle 7 closed: H.264 IDCT 8x8 = 151 Mblock/s NEON, Phase 4 deferred
M1: 10000/10000 bit-exact first try (column-major-block lesson from cycle 6 carried over cleanly). M3: 151.2 Mblock/s per core. Per-block 6.6 ns. 155x the 1080p30 floor (0.972 Mblock/s req'd). Phase-1 prediction of R7 = 0.5-0.9 YELLOW/GREEN was WRONG. H.264 IDCT 8x8 is dramatically lighter than VP9 IDCT 8x8 (18.5x faster NEON): VP9 IDCT 8x8: 122 ns/block (Q14 trig + COSPI multiplies) H.264 IDCT 8x8: 6.6 ns/block (pure integer butterfly + shifts) Phase 4 deferred via the cycle 6 lightweight-kernel rationale: NEON per-block << QPU dispatch floor; offload doesn't help. Phase 9 lesson updated: H.264 transforms (both 4x4 and 8x8) are NEON-trivial. Skip ALL H.264 transform cycles for QPU. Target compute-heavy H.264 kernels only (deblock = cycle 8 next; MC likely RED). Cycle 7 = 2nd consecutive "predicted GREEN, measured CPU-only" result. Forces a sharper view of which kernels QPU can actually help with: deblock and possibly some VP9 cases. - tests/h264_idct8_ref.c (column-major C ref) - tests/bench_neon_h264idct8.c (M1 + M3 bench) - CMakeLists.txt: cycle 7 bench wiring - docs/k7_h264idct8_phase3_and_4.md (closure) Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
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f92dc40f43 |
Cycle 6 (H.264) opened — IDCT 4x4 Phase 1+3, M3 = 175 Mblock/s
H.264 scope added 2026-05-18 per user direction. Pi 5's VideoCore VII has no hardware H.264 decoder block (only HEVC), so a QPU-accelerated H.264 path fills the most impactful codec gap. Cycle 6 = first H.264 kernel (4x4 IDCT + add, smallest H.264 transform, simplest first cycle). Phase 1: goal doc + 1080p30 floor analysis (5.85 Mblock/s worst-case, 2.0 Mblock/s realistic since most MBs use 8x8 or P-skip). Phase 3: NEON M3 baseline captured. ff_h264_idct_add_neon on hertz delivers 175 Mblock/s (5.7 ns per block) = 30x worst-case floor margin. H.264 IDCT 4x4 is dramatically lighter than VP9 IDCT 8x8 (21x faster per block). Phase 3 closure also caught the key Phase 9 lesson: H.264/FFmpeg blocks are COLUMN-MAJOR (block[c*4 + r] = (row=r, col=c)). NEON ld1 with 4 registers interleaves loading, and the FFmpeg C ref indexing makes this convention explicit. Initial C ref assumed row-major, M1 was 5% bit-exact; after fix, M1 = 100%. Convention encoded for all subsequent H.264 cycles (cycle 7+). - external/ffmpeg-snapshot/libavcodec/aarch64/h264idct_neon.S (vendored verbatim from FFmpeg n7.1.3, 415 lines) - external/ffmpeg-snapshot/PROVENANCE.md: updated - tests/h264_idct4_ref.c: column-major C ref - tests/bench_neon_h264idct4.c: M1 + M3 bench - CMakeLists.txt: cycle 6 NEON bench wiring - docs/k6_h264idct4_phase1.md, phase3.md Phase 4 next: QPU shader for cycle 6. Predicted R6 = 0.01 (deep RED — kernel too small relative to QPU dispatch overhead) but worth building for cycle-completeness + the opportunistic-helper hypothesis (cycle 6 may stay CPU per recipe). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
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eb5cfb34c4 |
Phase 8: wire LPF wd=4 + wd=8 QPU through public API
Mirror the IDCT pattern (lazy pipeline + per-call SSBO alloc + dispatch + readback) for cycles 2 (LPF wd=4) and 4 (LPF wd=8). Important caught-empirically bug: the two LPF shaders disagree on push-constant slot order — wd=4 puts dst_stride_u8 at slot 1, wd=8 puts it at slot 2 (with unused blocks_per_row at slot 1). Initial single-struct attempt silently corrupted wd=8 output (1958/2048 = 95.6 % bit-exact on test_api_lpf). Fixed by keeping separate lpf4_pc and lpf8_pc struct definitions. dst-window calc handles both kernels (same -4..+3 byte footprint per row). test_api_lpf exercises both kernels in CPU / QPU / AUTO modes against the C reference. All 6 mode/kernel combinations pass 2048/2048 bit-exact (32 edges × 8 rows × 8 bytes/edge). Phase 8 status after this commit: 3 of 5 kernels wired through API for QPU dispatch (IDCT, LPF wd=4, LPF wd=8 — i.e., all 3 QPU-default kernels per recipe). Cycle 3 MC and cycle 5 CDEF still need wiring for opportunistic-override mode but aren't needed for recipe-AUTO path. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
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1085c5699c |
Phase 8: wire IDCT QPU dispatch through public API
daedalus_ctx now owns a v3d_runner when V3D is available. The public API's dispatch_vp9_idct8 routes QPU calls through a new dispatch_idct8_qpu helper that: (1) lazy-creates the cycle 1 v4 pipeline on first use, (2) allocates 3 host-visible SSBOs per call (coeffs/dst/meta), (3) memcpy host->GPU, (4) dispatch with the v4 32-blocks-per-WG geometry, (5) memcpy GPU->host. Per-call alloc is intentional for Phase 8 correctness-first scope; buffer-pool perf optimization is deferred. Added daedalus_ctx_create_no_qpu() for fast-path callers that know they want CPU only. test_api_idct extended to a 3-mode matrix: CPU forced, QPU forced, AUTO recipe. All three deliver 4096/4096 bit-exact on hertz with V3D 7.1.7.0: recipe substrate for VP9_IDCT8: 2 (QPU) [CPU] 4096/4096 bit-exact [QPU] 4096/4096 bit-exact (real QPU dispatch through the API) [AUTO] 4096/4096 bit-exact (recipe routes to QPU) Next Phase 8 sub-step: same wiring pattern for cycle 2 LPF wd=4 and cycle 4 LPF wd=8 (the other two recipe-QPU kernels). Cycle 3 MC and cycle 5 CDEF only need the dispatch hook (recipe routes to CPU; QPU stays opportunistic via explicit override). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
|
760f6a4060 |
Phase 8 skeleton: public C API + first end-to-end smoke test
include/daedalus.h: stable C API surface exposing the 5 cycles (VP9 IDCT 8x8, LPF wd=4, MC 8h, LPF wd=8; AV1 CDEF). Per-kernel recipe-dispatch helpers default to the cycle 1-5 verdict substrate (QPU for cycles 1+2+4, CPU for cycles 3+5); explicit override available for benchmarking and runtime-aware scheduling. src/daedalus_core.c: NEON-path implementation of all 5 kernels wrapped behind the public API. QPU path stubbed out (returns -1) since wiring v3d_runner into daedalus_ctx is the next Phase 8 sub-step; with has_qpu=0 the recipe falls back to CPU cleanly. tests/test_api_idct.c: 64-block IDCT through the public recipe dispatch, bit-exact vs C ref. PASS 4096/4096 bytes — proves the API surface compiles, library links, dispatch routing works, and NEON fallback delivers correct results. docs/phase8_scoping.md: architecture options (A=userspace V4L2, B=kernel V4L2 shim, C=direct libva); pick A for v1; explicitly out-of-scope work tracked. Next Phase 8 sub-step: wire v3d_runner into daedalus_ctx so has_qpu=1 and QPU dispatch goes through the API too. After that: V4L2 ioctl glue, bitstream parser, superblock loop. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
|
5223d3cb3f |
Cycle 5 closed: CDEF QPU R5=0.116 ORANGE, opportunistic helper
Phase 4 plan with 3 Phase-5 REDs applied inline: - meta layout: m.z=tmp_off, m.w=dir - sec_shift clamped to >=0 (NEON uqsub semantics) - directions table as const ivec2[14], not OR-packed Phase 6 deliverable: v3d_cdef.comp (387 inst, 2 threads, no spills). 3-way M1 (QPU vs C ref vs NEON) PASS 4096/4096. M2: 0.443 Mblock/s -> R5 = 0.116 ORANGE (predicted 0.02-0.05 RED). M4 same-kernel: NEON-3+QPU 8.46 < NEON-4 alone ~10 (negative). M4 mixed (NEON-3 MC + QPU CDEF): CPU 34.17 Mblock/s MC, QPU 0.42 Mblock/s CDEF helper. CPU side higher than the Issue 003 NEON-fallback proxy suggested - cross-substrate contention is gentler than same-side NEON contention. Verdict: CDEF stays on CPU; QPU dispatch path exists for opportunistic use. Deployment recipe table updated for all 5 cycles. Phase 9 lessons: linear extrapolation across cycles is too pessimistic; CDEF is bandwidth-bound on NEON despite high per-block ns; real-substrate-cross contention < NEON-proxy contention. - src/v3d_cdef.comp: cycle 5 QPU shader - tests/bench_v3d_cdef.c: 3-way M1, M2 bench - tests/bench_concurrent_mixed.c: K_CDEF on both sides - tests/cdef_ref.c + bench_neon_cdef.c: sec_shift clamp + expanded damping range to exercise the edge case - CMakeLists.txt: v3d_cdef.spv + bench_v3d_cdef wiring - docs/k5_cdef_phase4.md updated with Phase 5 review applied - docs/k5_cdef_phase7.md: closure doc with full verdict matrix Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
|
2dd774a9ab |
Issue 003 closed: mixed-kernel M4 validates V4 deployment shape
bench_concurrent_mixed runs NEON-N on kernel A + QPU on kernel B concurrently. Matrix on hertz: V3 (CPU MC + QPU MC same-kernel): CPU 22.64 + QPU 0.39 Mblock/s V4 (CPU MC + QPU LPF4): CPU 27.87 + QPU 12.74 Medge/s V1 (CPU MC + NEON-fb CDEF): CPU 24.49 + 1.75 Mblock/s CDEF V2 (CPU LPF4 + NEON-fb CDEF): CPU 27.28 Medge + 1.70 Mblock/s V4 is the daedalus-fourier deployment shape (CPU runs MC; QPU runs LPF4 via cycle 2 GREEN offload). Both substrates productive; CPU MC +23% per-core vs same-kernel V3 control. Same-kernel M4 in cycles 1-5 was a worst-case contention bound, not a deployment number — user's "5%/50%" framing was correct. Cycle 3 MC verdict unchanged (QPU MC contributes ~0.4 under any contention); cycle 5 CDEF deferred verdict softened to opportunistic helper (NEON-fallback proxy used since cycle 5 Phase 6 not yet built). - tests/bench_concurrent_mixed.c (configurable cpu-kernel / qpu-kernel matrix; supports MC, LPF4, LPF8, IDCT real QPU dispatch; CDEF uses NEON-on-core-3 fallback) - CMakeLists.txt: build target wired with all FFmpeg + dav1d sources - docs/issues/003-mixed-kernel-m4-bench.md: closure + matrix - docs/k3_mc_phase7.md: M4 methodology caveat extended with V3/V4 - docs/k5_cdef_phase3_partial.md: deployment recommendation updated Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
|
20b59cd6a5 |
Cycle 5 phase 3 partial: M3 NEON = 3.923 Mblock/s; M1 deferred
CDEF is the most compute-intensive kernel measured so far —
254.9 ns/block (2x IDCT, 5x MC). 30fps@1080p floor margin: 4x
even on single NEON core in isolation.
M3 captured cleanly via dav1d_cdef_filter8_8bpc_neon. M1 bit-exact
gate failing due to tmp-layout mismatch between my standalone C
reference and dav1d's NEON expectation. The smoking gun: NEON output
appears at (+2 rows, -2 cols) shifted positions vs C ref output —
suggests NEON's padding-function output has a different convention
than my manual tmp construction.
Untangled in setup work:
- dav1d has TWO directions tables: stride-12 in src/tables.c
(C-side), stride-16 in src/arm/64/cdef_tmpl.S (NEON-side).
Initially vendored the C-side; should have used the NEON-side.
- dav1d's NEON expects tmp built by dav1d_cdef_padding8_8bpc_neon
(a separate function with its own conventions), not the C-side
padding() function from cdef_tmpl.c.
- Updated cdef_ref.c to use NEON-layout (stride 16) with table
transcribed from cdef_tmpl.S. Algorithm matches — but bench's
manual tmp construction doesn't match what NEON expects.
Resolution paths for next session (documented in
docs/k5_cdef_phase3_partial.md §'Resolution paths'):
1. Use dav1d_cdef_padding8_8bpc_neon to construct tmp (simplest)
2. Vendor dav1d's full C reference (most rigorous)
3. Reverse-engineer dav1d's padding output layout (hackiest)
Predicted R5 if/when QPU shader implemented: 0.02-0.05 (RED).
CDEF likely stays on CPU per cycle 3 lesson 7 (compute-bound
kernels don't benefit from QPU offload). 30fps floor still
passes regardless.
New artifacts:
- external/dav1d-snapshot/src/arm/64/cdef_tmpl.S (additional vendored)
- external/dav1d-snapshot/config.h — 14-define asm preamble shim
- tests/cdef_ref.c — standalone C ref (algorithmically correct,
layout mismatch with NEON known)
- tests/bench_neon_cdef.c — bench (M1 made warning, M3 captured)
- docs/k5_cdef_phase3_partial.md — phase 3 partial closure +
resumption checklist
dav1d snapshot in PROVENANCE.md should be updated next session
with the new cdef_tmpl.S entry.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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marfrit
|
85feba4087 |
Cycle 4 (LPF wd=8) closure: M1=100%, R=0.34, M4=+4.1%, PASS
Fourth daedalus-fourier kernel — VP9 8-tap inner loop filter wd=8 h_8_8 variant. Width extension of cycle 2's wd=4; completes VP9 inner-edge LPF coverage. Full cycle Phase 1-7 + M4'''' in one combined go (cycle compressed since incremental from cycle 2). Phase 5 review explicitly skipped (incremental ~30-line shader delta from cycle 2 + same geometry + cycle-2 RED-pattern checks still apply). Flagged in docs/k4_lpf8_phase4_7.md per dev_process.md "Skipping phases is a deliberate choice that should be flagged." Phase 6 v1 first-light: M1'''' 100.0000% bit-exact (65536/65536) first try. Shaderdb shows 231 inst, 4 hardware threads, 0 spills, 27 max-temps, 48 uniforms — compiler at the latency-hiding ceiling. Performance: M3'''' NEON (single-core) 52.382 Medge/s M2'''' QPU isolation 17.847 Medge/s R'''' 0.341 → ORANGE band 30fps floor margin 9.2x (isolation), 20.3x (mixed) M4'''' concurrent matrix: NEON 4-core 37.823 Medge/s <- baseline QPU only 14.867 Medge/s MIXED NEON-3 + QPU 39.389 Medge/s <- +4.1% PASS Verdict: YELLOW-via-M4'''' PASS. Deploy wd=8 LPF on QPU alongside cycle 2 wd=4. Combined VP9 inner-edge LPF coverage now complete. Cross-cycle LPF comparison: | | wd=4 (k2) | wd=8 (k4) | | M3 NEON | 48.3 | 52.4 | | M2 QPU iso | 19.6 | 17.8 | | R iso | 0.41 | 0.34 | | M4 delta | +6.9% | +4.1% | | 30fps mixed | 7.2x | 20.3x | | Verdict | GO QPU | GO QPU | NEW finding (Phase 9 lesson): NEON gets faster per edge as filter width grows (20.7 → 19.1 ns wd=4 → wd=8). The relative QPU loss grows with width. wd=16 would probably flip negative based on the trend line. Deployment recipe with cycle 4: IDCT 8x8 (k1) -> QPU (R=0.92, +7% mixed) LPF wd=4 (k2) -> QPU (R=0.41, +7% mixed) LPF wd=8 (k4) -> QPU (R=0.34, +4% mixed) MC 8h (k3) -> CPU (R=0.067, -19% mixed) Entropy -> CPU (structural) VP9 inner-edge LPF coverage complete. Project continues to higgs deployment plumbing or further kernels per user direction. New artifacts: - src/v3d_lpf_h_8_8.comp — GLSL shader - tests/vp9_lpf8_ref.c — standalone C ref - tests/bench_neon_lpf8.c — M1+M3 bench - tests/bench_v3d_lpf8.c — M1+M2 bench - tests/bench_concurrent_lpf8.c — M4 pthread bench - docs/k4_lpf8_phase1_3.md + phase4_7.md — combined cycle docs Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> |
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marfrit
|
356e446a49 |
Cycle 3 (MC interpolation) closure: M1'''=100%, R'''=0.067 RED, M4=-19.5%
Third daedalus-fourier kernel — VP9 8-tap regular subpel filter,
horizontal direction, 8-wide output. Multiply-heavy by design to
stress V3D's no-DP4A deficit. Full cycle Phase 1-7 + M4'''.
Phase 5''' second-model review delivered cleanly — caught 1 RED
bug pre-implementation (src_off off-by-3 indexing convention) and
2 YELLOW gaps (assert MUST language, shaderdb filter-LUT gate).
Without the review, M1''' would have failed silently on first run
with cryptic "high-index source pixels wrong" symptoms.
Phase 6 v1 first-light: M1''' 100.0000% bit-exact (65536/65536
blocks across all 16 mx phases). Phase 5''' filter-LUT prediction
materialised exactly: 197 uniforms (gate was 144), 2 threads (down
from cycle-2's 4 due to register pressure).
Performance:
M2''' = 1.413 Mblock/s (707.9 ns/block)
M3''' = 20.997 Mblock/s (NEON baseline phase3)
R''' = 0.067 (RED band — structural mismatch)
shaderdb: 488 inst, 2 threads, 197 uniforms, 25 max-temps, 0 spills
M4''' concurrent matrix (8s windows):
NEON 1-core 14.479 Mblock/s
NEON 4-core 15.248 Mblock/s <- baseline (compute-bound,
not bandwidth-saturated
like cycles 1+2!)
QPU only 1.380 Mblock/s
MIXED NEON-3 + QPU 12.277 Mblock/s <- -19.5% (FAIL gate)
MIXED NEON-4 + QPU 12.158 Mblock/s <- -20.3%
NEW cross-cycle finding (Phase 9 lesson 2): compute-bound CPU
workloads make the QPU-offload story collapse. Cycles 1+2 were
bandwidth-saturated (4-core scaling 0.56-0.82x of 1-core), so
freeing a CPU core via QPU offload added throughput. Cycle 3 MC
is compute-bound (4-core scaling 1.05x of 1-core — near-linear),
no free cycles to free. QPU contribution (0.45 Mblock/s in
contention) doesn't compensate for losing 1 NEON core delivering
~3.8 Mblock/s.
But 30fps@1080p floor: PASS in every config (1.4x to 15.7x
isolation margin). Per project_30fps_floor_is_fine.md, user-facing
test never fails — daily YouTube playback works fine on any CPU/QPU
split.
DEPLOYMENT RECIPE for higgs (cycle 3 confirmed split):
IDCT (k1) -> QPU (R=0.92, +7% mixed, frees CPU core)
LPF (k2) -> QPU (R=0.41, +7% mixed, frees CPU core)
MC (k3) -> CPU (R=0.067, -19.5% mixed — stays on CPU)
Entropy -> CPU (structurally serial)
Mixed-substrate deployment, not "QPU does everything". Realistic for
higgs: entropy + MC on 2-3 ARM cores; IDCT + LPF dispatched to QPU
concurrently; 1-2 ARM cores left for vscode etc.
New artifacts:
- src/v3d_mc_8h.comp — GLSL kernel
- tests/vp9_mc_ref.c — standalone C ref (REGULAR filter
embedded; clean transcription)
- tests/bench_neon_mc.c — M1'''_c + M3''' bench
- tests/bench_v3d_mc.c — M1''' + M2''' bench with contract
asserts + 30fps margin display
- tests/bench_concurrent_mc.c — M4''' pthread bench
- external/ffmpeg-snapshot/libavcodec/aarch64/vp9mc_neon.S (vendored)
- external/ffmpeg-snapshot/libavcodec/vp9_subpel_filters_table.c
(hand-extracted; provides
ff_vp9_subpel_filters symbol
without dragging in full vp9dsp.c)
- docs/k3_mc_phase{1,2,3,4,5,7}.md — full cycle documentation
Memory updates: project_30fps_floor_is_fine.md (user's 30fps target
recalibration), MEMORY.md index updated.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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|
marfrit
|
36eca40ff2 |
Cycle 2 (LPF) closure: M1''=100%, R''=0.41, M4''=+6.9%, PASS
Phase 4 plan + Phase 5 second-model review (PASS-WITH-REVISIONS:
2 YELLOW contract gaps applied) + Phase 6 v1 implementation +
Phase 7 verification including M4'' concurrent gate.
Phase 5'' review delivered cleanly — no RED bugs (cycle 1 lessons
applied successfully). 2 YELLOW findings baked into phase4 §4:
- stride >= 4 contract added alongside m.x >= 4 (finding 2)
- assert(...) in bench made a MUST not a suggestion (finding 4)
- V3D divergence-cost note: don't restructure to always-execute,
masked lanes consume clock anyway (finding 3, informational)
Phase 6 v1 first-light hit M1'' 100.0000% bit-exact on first run
(65536/65536 edges) — the cycle-1 v4 patterns (WG=256, 2-per-sg,
uint8_t SSBO, oob early-return discipline) baked in from start
worked as expected.
Performance:
M2'' = 19.645 Medge/s (50.9 ns/edge)
M3'' = 48.285 Medge/s (NEON baseline from phase3)
R'' = 0.41 (ORANGE band - doesn't auto-close per
cycle-1 calibration adjustment)
shaderdb: 160 inst, **4 threads**, 0 spills, 21 max-temps —
shader is already at the compiler ceiling. No v2/v3/v4 iteration
loop like cycle 1 because there's nothing more to extract from
the compiled shape. The 30x gap between theoretical instruction
throughput and measured wall-clock is divergence-tax + memory
latency, not compile quality.
M4'' concurrent matrix on hertz (8s windows):
NEON-1 LPF 41.131 Medge/s
NEON-4 LPF 33.726 Medge/s <- realistic CPU ceiling
(per-core 7-9; same
bandwidth-saturation as
cycle-1 F1)
QPU only 14.299 Medge/s
MIXED NEON-3 + QPU 36.049 Medge/s <- +6.9% over NEON-4
MIXED NEON-4 + QPU 31.892 Medge/s <- -5.4% oversubscribed
The "freed-core" pattern generalizes from IDCT to LPF: NEON-3+QPU
beats pure NEON-4 by ~7% in both cycles. Cycle-2 NEW finding:
**oversubscribed mode hurts for lighter kernels** (LPF -5.4% vs
cycle-1 IDCT +9.4%). Recommendation for higgs deployment hardens
to "always N-1 NEON cores + QPU, never N + QPU".
Phase 9 lessons (in phase7 §"Phase 9 lessons"):
1. Cycle-1 v4-pattern is the v1 starting point (saves 3 iterations)
2. Phase 5 review pays off every cycle
3. R isolation misleading on bandwidth-saturated hardware
4. Oversubscription tax depends on kernel weight
5. shaderdb 4-threads/0-spills = compute not the bottleneck
New artifacts:
- src/v3d_lpf_h_4_8.comp — GLSL kernel
- tests/bench_v3d_lpf.c — M1'' + M2'' harness with
contract asserts + fm/hev
pass-rate instrumentation
- tests/bench_concurrent_lpf.c — M4'' pthread bench
(mirrors bench_concurrent.c)
- docs/k2_deblock_phase{4,5,7}.md — plan + review + verification
Project verdict: continue. Cycle 3 candidates: MC interpolation
(multiply-heavy, stress V3D SMUL24), CDEF (AV1-only, different
neighborhood shape), or wd=8/wd=16 LPF variants. User to direct.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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marfrit
|
be7ff5587c |
Cycle 2 (deblocking) Phase 1-3: M3'' = 48.285 Medge/s baseline
Second kernel candidate per phase7_M4.md verdict "next-kernel cycle
authorised". VP9 4-tap inner loop filter, horizontal direction,
8-pixel edge (libavcodec ff_vp9_loop_filter_h_4_8_neon as baseline).
Different workload shape from IDCT - boundary streaming, lighter
compute per unit, per-row conditionals - tests whether QPU win
generalises.
docs/k2_deblock_phase1.md - goal-setting. Same R-band decision rules
as cycle 1 (phase1.md), with the cycle-1 calibration adjustment:
ORANGE band is no longer auto-close because M4 showed mixed > pure
CPU even at modest R when CPU bandwidth-saturates.
docs/k2_deblock_phase2.md - situation analysis. C reference already
in vendored snapshot (vp9dsp_template.c:1780-1898). Fetched
vp9lpf_neon.S fresh (1334 lines, LGPL-2.1+, FFmpeg n7.1.3 pin,
SHA-256 384e49e7...). PROVENANCE.md updated.
docs/k2_deblock_phase3.md - NEON baseline:
M1''_c bit-exact 100.0000 % (10000 random edges)
M3'' throughput 48.285 Medge/s (20.7 ns/edge, single A76)
per-frame 1080p-eq 748 FPS (worst case 64 530 edges/frame)
cycles/edge ~58 (=20.7ns x 2.8GHz), ~7 cycles/row
LPF is 5.9x faster per-unit than IDCT M3 (20.7 vs 122 ns), so the
QPU break-even point moves down. Predicted R''_v1 band ~0.5-0.9
- frame-level batching amortises the same 33us dispatch overhead;
workload becomes bandwidth-bound rather than compute-bound
(~5.7 MB/frame traffic at 64 530 edges x ~88 B per edge).
New artifacts:
- tests/vp9_lpf_ref.c - standalone bit-exact C ref (8-bit, wd=4
inner only; clean transcription)
- tests/bench_neon_lpf.c - M1''_c gate + M3'' time-based bench
(5s window, edge-content-biased RNG for
realistic fm/hev hit rates)
- external/ffmpeg-snapshot/libavcodec/aarch64/vp9lpf_neon.S
- CMakeLists.txt updated with bench_neon_lpf target
Phase 4 next: plan the QPU LPF compute shader. Cycle 1's phase4.md
+ phase5.md + phase7.md learnings apply directly - bake in the v4
winning patterns from the start (WG=256, edges-per-subgroup
pattern adapted from blocks, uint8_t dst SSBO, oob flag, unrolled
writes).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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|
marfrit
|
8182e43c15 |
Phase 7 M4: mixed CPU+QPU beats pure 4-core NEON; project continues
The YELLOW-band gate test from phase1.md (concurrent CPU+QPU vs
pure-CPU baseline). tests/bench_concurrent.c is a pthread harness
that runs N NEON workers (pinned to cores 0..N-1) and optionally a
QPU dispatch loop on its own pinned thread; 8s time-based windows;
sums per-worker block counts.
Raw results on hertz (1920x1088, 32640 blocks/dispatch):
Config Mblock/s 1080p FPS-eq
NEON 1-core 12.623 389.6
NEON 4-core 7.074 218.3 <- realistic CPU ceiling
QPU only 6.890 212.7
MIXED NEON-3 + QPU 7.583 234.0 <- +7.2 % over NEON-4
MIXED NEON-4 + QPU 7.739 238.9 <- +9.4 % oversubscribed
Headline findings beyond the gate test itself:
F1 — Pi 5 LPDDR4x saturates well before 4-core CPU scaling.
NEON-1 (12.6) > NEON-4 (7.1): 4 cores deliver 0.56x the
per-core throughput, not 4x. The realistic CPU ceiling for
memory-bound IDCT work is ~7 Mblock/s aggregate, not the
~32 Mblock/s a naive 4x scaling would predict. This recasts
phase7.md's R=0.92 framing: the right baseline is "4-core
NEON saturated", which the QPU effectively matches (6.89
vs 7.07) on its own.
F2 — QPU contributes meaningfully BECAUSE it doesn't fully share
the CPU's bandwidth bottleneck (own access channel + v3d L2
cache partially insulate it). Mixed adds the QPU's 0.51
Mblock/s on top of an already-saturated CPU.
F3 — Oversubscribed mode (NEON-4 + QPU) is not harmful — per-NEON
drops slightly but QPU adds more than the loss. Net +9 %.
F4 — Freed-core story is bigger than the throughput delta. In
mixed NEON-3+QPU, the 4th core is 100 % free for entropy
decode (Bool coder, ANS) which MUST run on CPU. Pure NEON-4
has nothing left. Realistic decode pipeline gets more like
a 30-50 % effective throughput uplift, not just 7 %.
Verdict per phase1.md YELLOW-band rule (mixed > pure-CPU): PASS.
Project continues to next-kernel cycle (recommend deblocking or
CDEF — same "small parallel block-level" workload class that
amortises the same M4 wins).
docs/phase7_M4.md captures the full M4 harness design, all 5
configs raw output, and the leaves-open items: M7 wall-power via
Himbeere plug, sustained-thermal test, realistic-bitstream
coefficient distribution, multi-frame async pipelining.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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|
marfrit
|
d66f22f333 |
Phase 6 (v1+v4 production) + Phase 7 closure: R = 0.92 ± 0.03 on hertz
First QPU IDCT8 kernel running and bit-exact on V3D 7.1 via Mesa
v3dv compute. Five iterations through a Phase 7→Phase 4' loopback;
production kernel is v4.
New files:
- src/v3d_runner.{c,h} — reusable Vulkan compute plumbing (instance,
V3D device picker, HOST_VISIBLE|COHERENT
SSBOs with mmap, compute pipeline from .spv,
enables storageBuffer{8,16}BitAccess)
- src/v3d_idct8.comp — VP9 8x8 DCT_DCT IDCT add, v4 production:
256 invocations/WG, 2 blocks/subgroup
(no idle lanes), uint8 dst SSBO (race-free
per phase5 finding 5), unrolled writes
(no chained ternary), oob-flag pattern
(barrier-safe per phase5 finding 7)
- tests/bench_v3d_idct.c — M1' bit-exact gate + M2 throughput vs C ref
- docs/phase7.md — full iteration journey + decision verdict
CMakeLists.txt updated to build the new shader, library, and bench
when DAEDALUS_BUILD_VULKAN=ON.
Iteration record (1920x1088 luma, 32640 blocks/dispatch, N=3):
ver change R ns/block
v1 first-light 0.230 533
v2 kill ternary + 2-blocks-per-sg 0.474 258
v3 per-pass scope oN 0.481 254 (noise)
v4 WG 64 -> 256 invocations 0.947 129
v5 packed uint32 coeff reads 0.938 130 (noise, reverted)
v4 final N=3 0.918 +/- 0.033
Bit-exactness 100.0000% across all iterations (10000-block sample
on 128x128, 32640-block sample on 1080p) against both the C
reference (tests/vp9_idct8_ref.c) and the vendored FFmpeg NEON
ff_vp9_idct_idct_8x8_add_neon.
Key learning over the Phase 5 review's prediction model: the
chained ternary was NOT a spill killer on V3D 7.1 (shaderdb
showed 0:0 spills:fills even in v1). The actual lever was
workgroup-size-driven latency hiding — going from 64 to 256
invocations doubled throughput with the same compiled code
(270 inst, 2 threads, 21 max-temps, 0 spills) because the
v3dv scheduler had 4x more in-flight work to overlap TMU
latency.
Verdict per phase1.md decision rules: YELLOW band (0.5 <= R < 1.0)
by a wide margin, near GREEN boundary. Phase 1 YELLOW rule:
add M4 (concurrent CPU+QPU throughput) before honest-close or
continue. M4 is the next measurement, not more shader tuning —
at R = 0.92 with all 4 A76 cores still 100% free for other work,
the question is whether the system aggregate beats pure 4-core
NEON.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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marfrit
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dcbbc77038 |
Path B pivot + Phase 0-3 closed with first baseline numbers
This is a from-scratch initial commit on a fresh .git. The original
scaffold commit (
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