fix: persistence is the trace's own phosphor, not a density behind a stroke
The plotter now deposits every acquisition -- the newest included -- into one grid per trace and
draws no solid trace over it, each grid in that trace's colour and with a one-sweep ceiling (its own
commit, **1b8b55d**). This side needed almost no change of its own, because the colour was already
the trace's and the trace's colour is `RowSet::signal_color()` -- the invariants' one route -- but the
figures it reads back are now per trace:
- **The ceiling is left at the library's default of one sweep**, no longer derived from the fade.
Deriving it from the steady state is the gain offset the user reported between the latest
acquisition and the persistent image; a signal crossing the same place every acquisition now settles
at the trace's colour, at full strength, and the newest sweep reads as the trace it is a picture of.
- **`cells`/`grid_bytes` are the sum over the row's traces** -- one grid each, a trace with no series
holding none -- and both the probe and the exit dump carry `traces=` beside `rows=`. That is what
makes the per-signal memory figure read: **556 537 cells and 2.2 MB per signal**, at 8904600 bytes
over the four one-signal rows of the probe's run.
The probes, re-read on this build (the `verification.md` command, `--rate 500000 --batch 1000`):
[density-probe] off enabled=0 ... rows=0 traces=0 cells=0 ink=0.0 peak=0.0000
[density-probe] on enabled=1 ... rows=4 traces=4 cells=2226150 ink=226786.0 peak=1.0000
[density-probe] step-acquisitions ... peak=1.5000
[density-probe] time-before ... peak=2.1359
[density-probe] step-time ... ratio=0.367879
[density-probe] frame cost: tick 0.62 -> 6.96 ms (184/23 frames), draw 2.02 -> 6.16 ms (177/18)
[udpscope] density: frames=748 rows=4 traces=4 cells=2226150 grid_bytes=8904600 ink=489400.2 peak=2.2 upload_bytes=2226150
`on` `peak=1.0000`, `step-acquisitions` `peak=1.5000` and `step-time` `ratio=0.367879` are the legs
that were expected, unchanged; the *draw* mean is now **below** the run before the split (2.02 -> 6.16
against 2.09 -> 20.91), because the solid traces are no longer drawn over the image.
Docs updated with it: the trigger manual page (`persistence` is the trace, one image per signal, the
newest included), the README's persistence section, `invariants-trigger-and-pinning.md` (five rules,
the ceiling and the no-stroke rule among them), `verification.md` and `probe-readings.md` (the lines
above), the trigger panel's comment and tooltips, and the plotter submodule.
`cmake --build build --clean-first -j4`: **0 errors, the documented three warnings** (two
`MathNode::source`, one `-Woverlength-strings` at 12352); `make -C build test-ui` **13 ok**;
`make -C build test-help` **green** (15 pages); the self-check **0 `Gtk-WARNING`/`Gtk-CRITICAL`** and
`gtk warnings: 0`, two `buffer allocated:` lines.
This commit is contained in:
Martino Ferrari committed
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@@ -376,21 +376,26 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
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trigger that has stopped firing never reaches another publish. A depth change is therefore also
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how the memory comes back.
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- **The phosphor density is one *image*, and that is a different display from the layers above, not a
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- **The phosphor density is the *trace*, and that is a different display from the layers above, not a
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mode of them.** The trigger panel's `Advanced` block offers both, and the words matter: *multiple
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events* is `persist_depth` (N retained acquisitions, N traces, dimmer with age) while *persistence*
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is `TriggerConfig::density` -- the plotter's `Plot::set_density()`, a screen-sized intensity grid
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every acquisition is deposited into and which fades either by a time constant or by a
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per-acquisition factor. There is **no depth** on the density and no per-acquisition memory: the
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image is `columns * rows * 4` bytes, one cell per device pixel of the row's axes (2.2 MB over the
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four rows of the probe's run), so a thousand acquisitions cost what one costs. A cell's value is a
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number of *sweeps*: the library deposits a cell once per trace per sweep however many of that
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trace's own samples crossed it (`[density-probe] on` reads `peak=1.0000` for one sweep; a per-hit
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deposit read 18) -- dwell is `Style::intensity_grading`'s question, not this one's.
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Four things hold it together, each of which is a rule:
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**per trace, drawn in that trace's own colour**, every acquisition deposited into it, which fades
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either by a time constant or by a per-acquisition factor. There is **no depth** on the density and
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no per-acquisition memory: the image is `traces * columns * rows * 4` bytes, one cell per device
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pixel of the row's axes for every trace the row draws (the app's default four signals in one row
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are four grids -- 6 MB at 800x480; the probe's one-signal-per-row run is 2.2 MB over four rows), so
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a thousand acquisitions cost what one costs. A cell's value is a number of *sweeps*: the library
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deposits a cell once per trace per sweep however many of that trace's own samples crossed it
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(`[density-probe] on` reads `peak=1.0000` for one sweep; a per-hit deposit read 18) -- dwell is
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`Style::intensity_grading`'s question, not this one's. The colour is the trace's own
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(`RowSet::signal_color()`, the same source the trace was built with and never a second one), so a
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saturated cell is that signal's colour at full strength and two signals agreeing in a cell are two
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quads of two colours rather than a blend.
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Five things hold it together, each of which is a rule:
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* **It is a trigger-mode display.** `apply_density()` (the tick) states `Held` and `Capturing` as
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the states it is on in; `Live`, `Waiting`, `Paused` and a file are not, and turning it off drops
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the grid **at once** rather than at an acquisition a quiet trigger never sends (the rule
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the grids **at once** rather than at an acquisition a quiet trigger never sends (the rule
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`set_persist_depth()` follows). So it goes away with the trigger, and a re-enable starts from an
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empty image rather than a stale one at another scale.
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* **One deposit per acquisition, one frame *after* the frame that frames it.** `Plot::accumulate_density()`
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@@ -403,21 +408,26 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
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* **The switch deposits what is already on screen.** `on && !density_was_on` sets the same pending
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flag, so a user who turns persistence on while an event is held sees it instead of waiting for a
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latch that `single` mode may never send.
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* **The brightness ceiling is the fade's steady state, and the ramp is linear in sweeps.** The app
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states `DensityConfig::full_scale` from the fade it configured -- `1/(1 - factor)` for the
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acquisition fade, the library's default two sweeps for the time one, which has no fixed steady
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state (it settles where the rate and the constant meet) -- and leaves `gamma` at 1.0. A ceiling
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at *one* sweep is the defect a user reported as "the colour fading is not applied, it looks
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white": a single sweep was already full ink, everything above it clamped to the same pixel, and
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a display of one sweep and a display of five were the same white. It is also the one half that
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the *grid's* own numbers cannot see -- `ink`/`peak` were right while the picture was flat -- so
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the assertion is a **framebuffer** one: `a_phosphor_density_is_drawn_under_the_traces` measures a
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cell at a quarter of the scale against one at the ceiling and against the background
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(`empty=21 full=83 quarter=54`), which is the reading the eye asked for.
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* **It is the plot's, so a figure rebuild resets it** -- the grid lives on each `Plot`, and
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* **No trace is drawn over it, and the newest acquisition is inside it.** `Renderer::draw_traces()`
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returns at once while a density is on: the trace ink *is* the image, so the acquisition just
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deposited is a sweep in it and fades with the rest. Drawing the polyline too put a solid,
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unfading stroke over its own faint ghost -- the reported "persistent image + last acquisition",
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where the last acquisition never faded in time mode -- and the assertion is a **framebuffer** one:
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`a_phosphor_density_is_the_trace_in_its_own_colour` reads the same pixel before and after one
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time constant and requires it dimmer (`full=224 -> faded=115`, the trace's own `0xE0` green),
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which a stroke over the density could not do.
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* **The brightness ceiling is the trace's own brightness, and the ramp is linear in sweeps.** The
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app leaves `DensityConfig::full_scale` at the library's default of **one sweep** and `gamma` at
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1.0, so the acquisition just deposited reads as the trace it is a picture of and a signal crossing
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the same place every acquisition settles *at* the trace's colour (the ceiling clamps), rather than
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a fraction of a brighter steady state. The old ceiling -- the fade's steady state, `1/(1-factor)`
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for the acquisition fade -- is the gain offset a user reported between the latest acquisition and
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the persistent image, and the "dimmer by design" headroom that made the ramp visible is reversed
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here.
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* **It is the plot's, so a figure rebuild resets it** -- the grids live on each `Plot`, and
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`rebuild_all()` builds new ones. That is the one state a structural change (a row added, a signal
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switched off, a trace recoloured) does not carry: it costs the accumulated image and nothing else,
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and the alternative -- keeping the grid in the `RowSet` -- is what would make it not a plot
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and the alternative -- keeping the grids in the `RowSet` -- is what would make it not a plot
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feature. The layout is unaffected either way: the density reserves no space and nothing on it can
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be picked, exactly as `set_invalid_spans()` does.
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* **The session carries it.** `trigger_density`, `trigger_density_decay`, `trigger_density_tau` and
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@@ -1980,53 +1980,61 @@ ring's bindings, and a reading taken there says nothing about either.
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```
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[density-probe] arming on 'square', window 0.5 s, display off
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[density-probe] off enabled=0 fade=acquisitions tau=1.000 factor=0.500 rows=0 cells=0 ink=0.0 peak=0.0000 ratio=1.000000
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[density-probe] on enabled=1 fade=acquisitions tau=1.000 factor=0.500 rows=4 cells=2226150 ink=226596.0 peak=1.0000 ratio=1.000000
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[density-probe] step-acquisitions enabled=1 fade=acquisitions tau=1.000 factor=0.500 rows=4 cells=2226150 ink=262722.0 peak=1.5000 ratio=1.159429
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[density-probe] time-before enabled=1 fade=time tau=1.000 factor=0.500 rows=4 cells=2226150 ink=213362.2 peak=1.2182 ratio=1.000000
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[density-probe] step-time enabled=1 fade=time tau=1.000 factor=0.500 rows=4 cells=2226150 ink=78491.6 peak=0.4481 ratio=0.367879
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[density-probe] frame cost: tick before=0.74 ms (163 frames) after=9.99 ms (12 frames) draw before=2.09 ms (157) after=20.91 ms (7)
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[udpscope] density: frames=504 rows=4 cells=2226150 grid_bytes=8904600 ink=632845.4 peak=2.8 upload_bytes=1081350
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[density-probe] off enabled=0 fade=acquisitions tau=1.000 factor=0.500 rows=0 traces=0 cells=0 ink=0.0 peak=0.0000 ratio=1.000000
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[density-probe] on enabled=1 fade=acquisitions tau=1.000 factor=0.500 rows=4 traces=4 cells=2226150 ink=226786.0 peak=1.0000 ratio=1.000000
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[density-probe] step-acquisitions enabled=1 fade=acquisitions tau=1.000 factor=0.500 rows=4 traces=4 cells=2226150 ink=313971.0 peak=1.5000 ratio=1.384437
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[density-probe] time-before enabled=1 fade=time tau=1.000 factor=0.500 rows=4 traces=4 cells=2226150 ink=458610.1 peak=2.1359 ratio=1.000000
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[density-probe] step-time enabled=1 fade=time tau=1.000 factor=0.500 rows=4 traces=4 cells=2226150 ink=168713.2 peak=0.7858 ratio=0.367879
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[density-probe] frame cost: tick before=0.62 ms (184 frames) after=6.96 ms (23 frames) draw before=2.02 ms (177) after=6.16 ms (18)
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[udpscope] density: frames=748 rows=4 traces=4 cells=2226150 grid_bytes=8904600 ink=489400.2 peak=2.2 upload_bytes=2226150
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```
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The **phosphor density** (`Plot::set_density()`, the trigger pane's `persistence` switch): one
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screen-sized intensity image per row, every acquisition accumulated into it, drawn behind the traces and
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fading by a count or by the clock. The numbers are the plotter's own -- `DensityGrid::ink()`/`peak()` summed
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and maxed over the rows the display is on, which is the same source the library's tests read -- and the
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screen-sized intensity image **per trace**, in that trace's own signal colour, every acquisition
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accumulated into it (the newest included), drawn *in place of* the traces and fading by a count or by
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the clock. The numbers are the plotter's own -- `DensityGrid::ink()`/`peak()` summed and maxed over the
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traces the display is on, which is the same source the library's tests read -- and the
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probe drives the panel's **own widgets** for the switch and the fade, so what it measures is this app's
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wiring.
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- **`off` is the display without it**: `rows=0`, so there is no grid at all and both numbers are zero.
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That is also the run the frame cost is read against, and it is a plain run -- the density is off by
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default and nothing draws it.
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- **`on` is one sweep**: `peak=1.0000` exactly, and `ink=226596` is the cells that sweep covered over
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four rows. A cell takes **1.0 once per trace per sweep** however many of the trace's own samples crossed
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it, which is what makes a sweep's peak *one* rather than the eighteen a per-hit deposit read on the same
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run -- and what makes the sweeps behind it visible at all.
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- **`off` is the display without it**: `rows=0 traces=0`, so there is no grid at all and both numbers
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are zero. That is also the run the frame cost is read against, and it is a plain run -- the density
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is off by default and nothing draws it.
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- **`on` is one sweep**: `traces=4` -- one grid per signal, four rows of one signal each -- and
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`peak=1.0000` exactly, with `ink=226786` the cells that sweep covered. A cell takes **1.0 once per
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trace per sweep** however many of the trace's own samples crossed it, which is what makes a sweep's
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peak *one* rather than the eighteen a per-hit deposit read on the same run -- and what makes the
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sweeps behind it visible at all.
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- **`step-acquisitions`** deposits one more sweep: `peak=1.0000 -> 1.5000`, which is `1 + 0.5 x 1` -- the
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panel's factor 0.5 applied to what was there, then the new sweep's own pass on top. `ink` rises from
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`226596` to `262722` for the same reason: the old image halved and one sweep landed on it. The ratio is
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panel's factor 0.5 applied to what was there, then the new sweep's own pass on top. The ratio is
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**not** a constant to expect -- the acquisition on screen can move between the two reads, so what it says
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is "the old image halved and a pass landed on it"; the exact relation is the *library's* case
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(`a_density_halves_per_acquisition_and_keeps_the_newest_brightest`), where the same frame is deposited
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twice.
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- **`step-time` is `1/e` by construction**: one step of `dt = tau` through the plot's own `decay_density()`,
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so `ratio=0.367879` is `exp(-1)`. The leg before it (`time-before`) reads the same image under the time
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fade, and the pair is the reading that says the *panel's* constant reaches the grid.
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fade (`peak=2.1359`), and the pair is the reading that says the *panel's* constant reaches the grid.
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- **`frame cost:` is the A/B inside one run**: the accumulators as of the tick the display was switched on
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against the frames after it, so both means are the same stream, the same layout and the same mock. At four
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rows of 573x412 cells it reads **tick 0.74 -> 9.99 ms** and **draw 2.09 -> 20.91 ms**: the per-frame
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rows of 573x412 cells it reads **tick 0.62 -> 6.96 ms** and **draw 2.02 -> 6.16 ms**: the per-frame
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conversion, upload and deposit. It is llvmpipe, and the arithmetic is the grid's -- 2.2 M cells, one byte
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each, every frame the time fade moves it.
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each, every frame the time fade moves it. The *draw* mean is now below the run before the per-trace
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split (2.02 -> 6.16 against 2.09 -> 20.91): the solid traces are no longer drawn over the image, so the
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frame draws four quads where it used to draw four quads *and* every trace.
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- **`cells`/`grid_bytes` are the per-signal memory figure**: 556 537 cells and 2.2 MB *per signal*, times
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the four signals here (2 226 150 cells, 8 904 600 bytes). It is the axes rect's device pixels, so it is
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the screen and the trace count and nothing the trigger has done -- and the app's default layout, four
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signals in one row, is four grids for that one row.
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- **The dump's `density:` line** is captured on the last tick the display was **on**, not read at exit: the
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exit probe switches the trigger off before it dumps, which takes the display with it, so a dump that asked
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the plots would say `rows=0` about a run whose tail had the image up. `upload_bytes` is the **most** any
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one frame uploaded -- one byte a cell, over the rows that moved -- and not the last frame's, for the same
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reason.
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one frame uploaded -- one byte a cell **per trace**, over the grids that moved -- and not the last frame's,
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for the same reason.
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**Read `peak` as the display's ceiling**: with the default `full_scale` of 1.0 a cell at 1.0 is full ink, so
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a steady display under the acquisition fade sits between 1 and 2, and a `peak` well above that (the
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per-hit deposit read 189 after two sweeps) is the defect this probe's `on` leg now catches.
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**Read `peak` as the display's ceiling**: with the default `full_scale` of 1.0 a cell at 1.0 is full ink
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(the trace's own colour), so a steady display under the acquisition fade sits between 1 and 2, and a `peak`
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well above that (the per-hit deposit read 189 after two sweeps) is the defect this probe's `on` leg now
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catches.
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**And `N = 1` is the display without the feature**, which is the same command at
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`UDPSCOPE_PROBE_PERSIST_DEPTH=1`:
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@@ -115,8 +115,9 @@ precedent, not an exception.
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schedule in use, oldest first — halves, and `1/2^age` at that. Both lines and the two exit-dump
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lines are in [probe-readings.md](probe-readings.md).
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- `UDPSCOPE_PROBE_DENSITY_MS` (+ `UDPSCOPE_PROBE_DENSITY_TAU`, default 1.0 s) — the **phosphor
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density**: one screen-sized intensity image every triggered acquisition is accumulated into, drawn
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behind the traces, fading by a per-acquisition factor or by a time constant. It states the display
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density**: one screen-sized intensity image **per trace**, in that trace's own colour, every
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triggered acquisition accumulated into it (the newest included), drawn *in place of* the traces,
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fading by a per-acquisition factor or by a time constant. It states the display
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**off** through the panel's own switch first, so the `off` leg is the run without it, then arms the
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trigger on the mock's `square` with one signal per row — the arrangement the persistence probe uses
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— and only then switches it on, so the acquisition already on screen is the first image. Four legs,
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@@ -131,8 +132,9 @@ precedent, not an exception.
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kill $PY
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```
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**The assertions, in order:** `off` reads `rows=0 cells=0 ink=0.0 peak=0.0000` (there is no grid at
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all); `on` reads `rows=4` — every row has its own image — and **`peak=1.0000`**, one sweep's ink
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**The assertions, in order:** `off` reads `rows=0 traces=0 cells=0 ink=0.0 peak=0.0000` (there is no
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grid at all); `on` reads `rows=4` — every row has its own image, one per trace in its own colour,
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so `traces=4` with one signal a row — and **`peak=1.0000`**, one sweep's ink
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being one per cell it covers; `step-acquisitions` reads **`peak=1.5000`**, which is the panel's
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0.5 applied to the old image plus the new sweep's own pass; and `step-time` reads
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**`ratio=0.367879`**, one step of `dt = tau` through the plot's own `decay_density()`. A `peak` in
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