Files
Dragon-s-Lair-X68k/tools/bench/verify_decode.py
T
prosolis 7d365b3ff5 Drop SASI on capacity, then find the budget never had the disk in it
USER DECISION: drop the `sasi` profile. Not on bandwidth -- on capacity. A SASI
volume is 40 MB, and the 22.8 min of unique scene footage on the source Blu-ray
(streams 00000-00201, measured, not recalled) is 146 MiB at the LOWEST rate this
codec makes -- more than the machine's whole 4-unit SASI space. `scsi` is the
only profile now. FINDINGS 32.

Then the user asked whether we were drawing the wrong conclusions about PIO vs
DMA, and we were, more broadly than the question implied. Every CPU figure in
FINDINGS 24-34 is scored against the full 833,333 cycles/frame with nothing
subtracted for moving the bitstream off disk. Debiting the HD63450 cycle-steal
at the long-standing 8 clk/word ESTIMATE, "1 frame of 120 misses" becomes 84 of
120, median 112.4%. PIO at the span rate is 99.8% of the machine. Spans buy
cycles by spending bandwidth and the bandwidth returns as steal, so 31.6's "fits
completely" becomes a worst frame of 114.3%. 10 fps absorbs it: median 93.7%,
1/120. FINDINGS 35. `11_cpu_budget.py` takes --io dma|pio|none, defaults to dma,
and warns if asked for none.

Also landed:
- item 1 done: the cost model checked against the 68000 on a cost-aware
  container, -3.07% to +0.01%, whole-window mean -1.22%. FINDINGS 34.
- item 4 done: the container carries its own 4-byte record alignment (DLX2).
  94/120 record starts were on odd addresses -- an address error, not a slow
  read -- now 0/120 for 16 B/s. Re-encoding reproduces 31.1 exactly. FINDINGS 33.
- a `scsi` window does not fit the 2 MB machine the rig emulates (2.84 MB of
  stream past a 0x200000 ceiling). The gate now verifies 80 of 120 frames and
  SAYS so, and fails loudly when the pass does not complete, instead of
  reporting a phantom 49,005-pixel diff. FINDINGS 36.

Three near-misses this session had one shape: an unobservable run nearly
produced a false finding. stdbuf -oL on any MAME job that prints progress -- a
file is block-buffered too, and a run that is merely finishing looks exactly
like one that is wedged.

check.sh ALL GREEN.

Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
2026-08-23 17:09:47 -07:00

76 lines
3.0 KiB
Python

#!/usr/bin/env python3
"""Is the 68000 decoder's output pixel-exact against the reference decoder?
python3 tools/bench/verify_decode.py <in.dlx> [--snap tmp/snap_decode]
Checks tmp/snap_decode/x68000/0000.png -- the screen after src/player/decode.s
has decoded every frame of the container in sequence -- against
tools/encoder/dlx.py's reconstruction of the final frame.
This is a stronger test than the blit regression it is modelled on. The blit
proved the 68000 could COPY a frame; this proves it can PARSE one. And because
the decoder is temporally recursive -- a SKIP block is a claim that the previous
frame is still in GVRAM -- the last frame of a sequential run is only correct if
every frame before it was, so a single comparison audits all of them.
"""
import argparse, sys
sys.path.insert(0, "tools/encoder")
import numpy as np
from PIL import Image
from dlx import DLX
ap = argparse.ArgumentParser()
ap.add_argument("container")
ap.add_argument("--snap", default="tmp/snap_decode")
# The harness can only load as much of a container as fits in the emulated
# machine's RAM, so it may have decoded a PREFIX (tools/bench/prep_dlx.py
# --ram). Compare against the same prefix, or the reference runs ahead of the
# 68000 and reports a mismatch that is an artefact of the rig.
ap.add_argument("--nframes", type=int, default=None,
help="frames the 68000 actually decoded (default: all)")
a = ap.parse_args()
d = DLX(a.container)
NF = a.nframes if a.nframes is not None else d.nframes
if NF > d.nframes:
sys.exit(f"--nframes {NF} exceeds the container's {d.nframes}")
canvas = np.zeros((d.H, d.W), np.uint8)
for f in range(NF):
d.paint(canvas, f)
pal = d.pal.astype(int)
p6 = lambda v: ((v << 2) | (v >> 4)) & 0xFF
fl = pal >> 3
render = lambda I: p6((fl << 1) | I[:, None])
I = (((render(np.ones(256, int)) - pal) ** 2).sum(1)
< ((render(np.zeros(256, int)) - pal) ** 2).sum(1)).astype(int)
exp = render(I)[canvas]
s = np.asarray(Image.open(f"{a.snap}/x68000/0000.png").convert("RGB")).astype(int)
fail = []
if s.shape[:2] != (512, 256):
fail.append(f"1. geometry: expected 512x256, got {s.shape[1]}x{s.shape[0]}")
else:
if not all(np.array_equal(s[i], s[i+1]) for i in range(1, s.shape[0]-1, 2)):
fail.append("2. double-scan pairing (1,2),(3,4),... broken")
g = s[0::2]
yoff = (g.shape[0] - d.H) // 2
act = g[yoff:yoff+d.H]
if not np.array_equal(act, exp):
diff = abs(act - exp)
bad = diff.any(2)
by, bx = np.where(bad)
blocks = sorted(set(zip((by//4).tolist(), (bx//4).tolist())))
fail.append(f"3. frame {NF-1} not pixel-exact: {bad.sum()} px in "
f"{len(blocks)} blocks differ, maxdiff {diff.max()}; "
f"first block (by={blocks[0][0]}, bx={blocks[0][1]})")
for x in fail:
print("FAIL " + x)
if fail:
sys.exit(1)
print(f"OK {NF} frames decoded on the 68000, final frame pixel-exact "
f"against tools/encoder/dlx.py")
print(f" {d.W}x{d.H}, {d.nb} blocks/frame, k1={d.k1} k4={d.k4}, "
f"all four block modes exercised")