Files
sras-viewer/sras_workers.py
T
Thomas Ales 8348ad313c Implement FFT pad-factor caching and the stored-cache display fast path
tests/test_stored_cache.py exercised two features that were never built,
so six of its tests had been failing on main. Both are now implemented.

Pad-factor caching. A padded view could not use a stored FFT cache at all:
the store was pad 1 by definition and cached_rf_image rejected any n_fft
outright, so a user working at a pad factor got nothing from batch-computing
a file. CACH tail v3 records the pad the images were resolved at, cache_file
computes at a requested pad, and the batch actions pass the viewer's own pad
down — while still refusing a store resolved at a different pad, since a
padded FFT interpolates between the natural bins and so resolves genuinely
different peak frequencies. v1/v2 tails read as pad 1 and keep working.

Stored-cache dispatch. _refresh_display only ever consulted this window's
in-session dicts, so after a batch every angle change still queued a worker
and a progress popup for an image already on disk — the exact cost the batch
was run to avoid. It now checks the file's own DC/FFT blocks first, asking
with allow_dc_recompute=False so the GUI thread never touches I/O. When the
stored cache genuinely cannot serve the view, the scan info panel says why
rather than leaving the silent recompute a mystery.

Two bugs surfaced on the way:

- The angle spinbox was wired on editingFinished, which QAbstractSpinBox
  emits only on Return or focus-out — never on a step. Clicking its arrows,
  the ordinary way to walk a scan, moved the number and left the image
  behind. Now valueChanged with keyboard tracking off, which fires on a step
  and once on commit, but not per keystroke mid-typing. Every existing GUI
  test called _on_view_changed() by hand and so could not have caught this;
  two new tests pin it and fail against the old wiring.

- A plain "fft" batch over a file previously cached with fft_rowavg carried
  the old row_avg_n forward, labelling raw images as row-averaged. It now
  writes row_avg_n=0 explicitly.

Verified: 111 passed (was 103 passed / 6 failed), and
tools/check_equivalence.py is byte-identical to the pre-change baseline.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-08-09 13:50:37 -05:00

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#!/usr/bin/env python3
"""Background workers for the SRAS viewer.
Every worker is a plain QObject moved onto its own QThread by
SrasViewerWindow._run_worker, exposing signals only. Workers must never touch
GUI-thread-owned state (the display caches in particular) — they take
everything they need through their constructor and hand results back by signal.
"""
import os
from concurrent.futures import ProcessPoolExecutor, ThreadPoolExecutor, as_completed
from concurrent.futures.process import BrokenProcessPool
import numpy as np
from PyQt6.QtCore import QObject, pyqtSignal
import sras_compute as compute
from sras_align_export import write_aligned_sras
from sras_compute import cache_file, compute_rf_image, dc_image_mv
from sras_format import CH3_IDX, CH4_IDX, SrasFile
# Concurrency caps. Batch conversion runs one process per file, and each of
# those processes threads internally, so the two must be divided rather than
# both set to the core count. Files also commonly sit on one external drive,
# where a dozen concurrent readers is slower than a few — hence the low
# default, overridable from the environment.
_BATCH_MAX_PROCS = int(os.environ.get("SRAS_BATCH_PROCS", 0)) or min(
4, os.cpu_count() or 2)
# Spawning a pool costs roughly a second of interpreter startup (each child
# re-imports the entry module). That is noise against a multi-GB scan but
# dominates a batch of small files, where it would make the job *slower* —
# so below this total size the batch just runs in the worker thread.
_BATCH_POOL_MIN_BYTES = int(os.environ.get("SRAS_BATCH_POOL_MIN_MB", 512)) * 1024 * 1024
class CancellableWorker(QObject):
"""A worker whose compute polls stop() between row chunks.
Without this a shutdown has to wait out whatever is in flight, and on a
large scan a single angle is ~40 s — far too long to block closing the
window. Chunk-level polling bounds the wait to one chunk instead.
"""
def __init__(self):
super().__init__()
self._stop = False
def stop(self):
self._stop = True
def _stopped(self) -> bool:
return self._stop
class _PooledWorker(CancellableWorker):
"""Fans a per-item computation across a thread pool, emitting each result
from this worker's own thread as it lands (never from a pool thread).
Subclasses provide _plan() -> n_workers (stashing whatever per-run
context they need), _items(), _one(item) -> result, and _emit(result).
On stop(): queued items are dropped, in-flight ones are not waited for —
that is what keeps closing the window responsive on a large scan.
"""
finished = pyqtSignal()
error = pyqtSignal(str)
def run(self):
try:
pool = ThreadPoolExecutor(max_workers=max(1, self._plan()))
try:
futures = [pool.submit(self._one, it) for it in self._items()]
for fut in as_completed(futures):
if self._stop:
break
self._emit(fut.result())
finally:
pool.shutdown(wait=not self._stop, cancel_futures=True)
self.finished.emit()
except Exception as exc:
self.error.emit(str(exc))
class LoadWorker(QObject):
finished = pyqtSignal(object) # SrasFile | None
error = pyqtSignal(str)
def __init__(self, path: str):
super().__init__()
self._path = path
def run(self):
try:
self.finished.emit(SrasFile(self._path))
except Exception as exc:
self.error.emit(str(exc))
self.finished.emit(None)
class ComputeWorker(CancellableWorker):
"""Computes one displayable image for (angle, channel).
For CH1/Velocity (FFT-derived) channels, the FFT is only run for pixels
whose DC4 (Bias B) mean is at or above dc_threshold_mv — masked pixels are
left at 0 MHz without ever being FFT'd, since that's the expensive part of
a scan. If the DC4 image for this angle is already known, pass it in as
*dc4_mv* to skip re-reading the CH4 channel from disk entirely.
Emits a plain ``np.ndarray`` already in display units.
"""
finished = pyqtSignal(object)
error = pyqtSignal(str)
def __init__(self, sras: SrasFile, angle_idx: int, ch_idx: int,
apply_bg_sub: bool = True, n_fft: int | None = None,
dc_threshold_mv: float = 0.0,
dc4_mv: np.ndarray | None = None,
is_fft_mode: bool = False):
super().__init__()
self._sras = sras
self._angle = angle_idx
self._ch = ch_idx
self._apply_bg_sub = apply_bg_sub
self._n_fft = n_fft
self._dc_threshold = dc_threshold_mv
self._dc4_mv = dc4_mv
self._is_fft_mode = is_fft_mode
def run(self):
try:
if self._is_fft_mode:
img = compute_rf_image(
self._sras, self._angle, dc_threshold_mv=self._dc_threshold,
apply_bg_sub=self._apply_bg_sub, n_fft=self._n_fft,
dc4_mv=self._dc4_mv, should_stop=self._stopped)
else:
img = dc_image_mv(self._sras, self._angle, self._ch,
should_stop=self._stopped)
# On cancellation the image is only partly filled, so hand back
# None rather than something that would be cached as real. The
# signal still fires either way — it is what quits the thread.
self.finished.emit(None if self._stop else img)
except Exception as exc:
self.error.emit(str(exc))
class DcPrecomputeWorker(_PooledWorker):
"""Computes CH3/CH4 DC images for every angle in the background.
DC images are cheap (a per-waveform mean, no FFT) compared to the
CH1/Velocity FFT, so precomputing them for the whole file right after load
makes switching angles instant while on a DC channel, and also means the
FFT masking step (which needs a DC4 image) rarely has to wait on anything.
"""
angle_done = pyqtSignal(int, np.ndarray, np.ndarray) # angle_idx, dc3_mv, dc4_mv
def __init__(self, sras: SrasFile):
super().__init__()
self._sras = sras
self._angle_budget = 0
def _plan(self) -> int:
n_workers, self._angle_budget = compute.plan_angle_level(self._sras)
return n_workers
def _items(self):
return range(self._sras.n_angles)
def _one(self, a: int) -> tuple[int, np.ndarray, np.ndarray]:
# max_workers=1 *and* a budget share: this call is one of several
# concurrent angles, and both the thread count and the buffer size
# have to be divided (see compute.plan_angle_level).
kw = dict(max_workers=1, budget=self._angle_budget,
should_stop=self._stopped)
return (a,
dc_image_mv(self._sras, a, CH3_IDX, **kw),
dc_image_mv(self._sras, a, CH4_IDX, **kw))
def _emit(self, result):
self.angle_done.emit(*result)
class BatchCacheWorker(QObject):
"""Batch-computes and stores DC or FFT images into each of *paths*'s v7
CACH tail, in place — converting v6 sources to v7 on first use, or updating
an existing v7 file's cache blocks without disturbing whatever the other
block already holds.
*mode* is ``"dc"`` (CH3/CH4 mean images), ``"fft"`` (CH1 peak-frequency
images, unmasked — masking is applied at display time, same as v5's PREC
convention), or ``"fft_rowavg"`` (same-row, distance-weighted CH1
averaging before the FFT — needs *dc_threshold_mv* and a positive
*row_avg_n*; see ``sras_compute.cache_file``).
Both FFT modes cache at *pad_factor*, which the caller sets from the
viewer's own padding — a cache stored at a pad the user is not viewing
at is one the display can never use.
Files are processed one per subprocess: they are fully independent, each
opens its own memmap and writes only its own bytes, and only path strings
and scalars cross the process boundary. Emits ``progress(int)`` (0–100 by
files completed), ``file_done(str, str)`` (path, error message or "") so
one file's failure doesn't abort the batch, and ``finished()``.
"""
progress = pyqtSignal(int)
file_done = pyqtSignal(str, str)
finished = pyqtSignal()
def __init__(self, paths: list[str], mode: str, apply_bg_sub: bool,
dc_threshold_mv: float | None = None, row_avg_n: int = 0,
pad_factor: int = 1):
super().__init__()
self._paths = paths
self._mode = mode
self._apply_bg_sub = apply_bg_sub
self._dc_threshold = dc_threshold_mv
self._row_avg_n = row_avg_n
self._pad_factor = pad_factor
def _report(self, path: str, err: str, done: int, total: int):
self.file_done.emit(path, err)
self.progress.emit(int(done / max(1, total) * 100))
def _run_pooled(self, paths: list[str], n_procs: int) -> list[str]:
"""Process the batch across *n_procs* subprocesses. Returns the paths
that never got a real answer because the pool itself died, so the
caller can retry them in-process.
Under spawn each child re-imports the entry module, so the batch must
survive that going wrong (an unguarded __main__, a frozen build, a
sandbox that forbids subprocesses) rather than reporting every file as
failed — hence the retry list instead of a per-file error.
"""
# Each child threads internally; divide the machine rather than
# letting every process claim every core.
per_proc_workers = max(1, (os.cpu_count() or 4) // n_procs)
unresolved: list[str] = []
done = 0
with ProcessPoolExecutor(max_workers=n_procs) as executor:
futures = {
executor.submit(cache_file, p, self._mode, self._apply_bg_sub,
compute.get_fft_backend(), per_proc_workers,
pad_factor=self._pad_factor,
dc_threshold_mv=self._dc_threshold,
row_avg_n=self._row_avg_n): p
for p in paths
}
for fut in as_completed(futures):
path = futures[fut]
try:
err = fut.result()
except BrokenProcessPool:
unresolved.append(path)
continue
except Exception as exc:
err = str(exc)
done += 1
self._report(path, err, done, len(paths))
return unresolved
def _run_inline(self, paths: list[str], done: int, total: int):
"""Fallback / single-file path: compute in this thread. Still uses the
full core count internally, since nothing else is competing."""
for path in paths:
try:
err = cache_file(path, self._mode, self._apply_bg_sub,
compute.get_fft_backend(),
compute.default_max_workers(),
pad_factor=self._pad_factor,
dc_threshold_mv=self._dc_threshold,
row_avg_n=self._row_avg_n)
except Exception as exc:
err = str(exc)
done += 1
self._report(path, err, done, total)
def _worth_pooling(self, paths: list[str]) -> bool:
if len(paths) < 2:
return False
total = 0
for p in paths:
try:
total += os.path.getsize(p)
except OSError:
pass # unreadable files are reported by cache_file
return total >= _BATCH_POOL_MIN_BYTES
def run(self):
paths = self._paths
n_procs = max(1, min(_BATCH_MAX_PROCS, len(paths)))
if not self._worth_pooling(paths):
self._run_inline(paths, 0, len(paths))
self.finished.emit()
return
try:
unresolved = self._run_pooled(paths, n_procs)
except Exception:
# The pool could not be created or collapsed wholesale.
unresolved = list(paths)
if unresolved:
self._run_inline(unresolved, len(paths) - len(unresolved), len(paths))
self.finished.emit()
class Ch4MaskWorker(_PooledWorker):
"""Fetches each requested angle's CH4 (Bias B) DC image in mV, for the
alignment wizard's initial threshold-mask stack.
Reuses dc_image_mv, which prefers a stored v5/v7 cache over recomputing
from raw waveforms, so this only does real work for a file that hasn't
gone through the v7 "Convert" batch step and for angles the main
window's own DcPrecomputeWorker (which runs automatically right after
every file load) hasn't reached yet. In the common case — the user opens
Fusion -> Manual Alignment after DC precompute has already finished —
*angle_indices* is empty and this worker is never even constructed (see
CorrelatePage._start_mask_prep).
"""
angle_done = pyqtSignal(int, np.ndarray) # angle_idx, dc4_mv
def __init__(self, sras: SrasFile, angle_indices: list[int]):
super().__init__()
self._sras = sras
self._angles = angle_indices
self._budget = 0
def _plan(self) -> int:
n_workers, self._budget = compute.plan_angle_level(self._sras)
return n_workers
def _items(self):
return self._angles
def _one(self, a: int) -> tuple[int, np.ndarray]:
return a, dc_image_mv(self._sras, a, CH4_IDX,
max_workers=1, budget=self._budget)
def _emit(self, result):
self.angle_done.emit(*result)
class CrossCorrelateWorker(_PooledWorker):
"""Rigid registration (rotation + translation, never scale) of each of
*angle_indices* against *ref_angle_idx*, for the alignment wizard's
Run/Re-run Correlation button.
Runs on a background thread — registering a real many-angle,
high-resolution scan takes long enough that doing it on the GUI thread
would visibly freeze the dialog. Rotation is *searched*, not taken from the
stage's reported angle: see compute.register_angle_to_reference, which
seeds from that angle but scores both of its signs and refines from there.
dc4_mv is the dialog's own already-in-memory per-angle CH4 image — this
worker does no fetching of its own.
"""
# angle_idx, rotation_deg, shift_x_mm, shift_y_mm, score, source
angle_done = pyqtSignal(int, float, float, float, float, str)
def __init__(self, sras: SrasFile, ref_angle_idx: int, angle_indices: list[int],
dc4_mv: dict[int, np.ndarray], *,
sources: tuple[str, ...], dc_threshold_mv: float,
search_deg: float, reg_kwargs: dict | None = None):
"""*reg_kwargs* is splatted into register_angle_to_reference on top of
the named arguments — the wizard's rotation-search controls (seed,
signs, refine, grid sizes) go through here, so exposing another knob
needs no change to this class."""
super().__init__()
self._sras = sras
self._ref = ref_angle_idx
self._angles = angle_indices
self._dc4_mv = dc4_mv
self._sources = sources
self._threshold = dc_threshold_mv
self._search_deg = search_deg
self._reg_kwargs = dict(reg_kwargs or {})
def _plan(self) -> int:
return compute.registration_workers(self._sras)
def _items(self):
return self._angles
def _one(self, a: int) -> tuple[int, compute.RigidFit]:
return a, compute.register_angle_to_reference(
self._sras, a, self._ref, self._dc4_mv,
dc_threshold_mv=self._threshold, sources=self._sources,
search_deg=self._search_deg, **self._reg_kwargs)
def _emit(self, result):
a, fit = result
self.angle_done.emit(a, fit.rotation_deg, fit.shift_mm[0],
fit.shift_mm[1], fit.score, fit.source)
class AlignedExportWorker(CancellableWorker):
"""Writes the aligned, cropped .sras on a background thread.
Unlike every other worker here this one produces a *file*, which changes
what cancellation has to mean: write_aligned_sras stages into a ".part"
sibling and removes it when should_stop() fires, so a cancelled or crashed
export leaves nothing behind. That matters more than it sounds — a
truncated .sras is not detectably broken, since the v6 parser reads a short
file as an aborted scan and opens it happily.
Cancellation is polled per output row chunk, the same granularity
CancellableWorker's docstring justifies, so closing the window never waits
on a multi-gigabyte write.
"""
progress = pyqtSignal(int) # 0-100
finished = pyqtSignal(str, str) # written path ("" = none), error
def __init__(self, sras: SrasFile, result, out_path: str):
super().__init__()
self._sras = sras
self._result = result
self._out_path = out_path
def run(self):
try:
written = write_aligned_sras(
self._sras, self._result, self._out_path,
progress_cb=self.progress.emit, should_stop=self._stopped)
if self._stopped():
self.finished.emit("", "") # cancelled: no file, no error
else:
self.finished.emit(str(written), "")
except Exception as exc:
self.finished.emit("", str(exc))