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Use ring offsets for spectrum history

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Meta Vens 2026-05-27 11:55:46 +01:00
commit b44aaac7cc
6 changed files with 26 additions and 8 deletions
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4
docs/implementation-plan.md
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@ -154,7 +154,9 @@ a named invariant that the native runtime cannot protect yet.
topology changes do not resize the GPU buffer while the trail fills.
`MIMIR_SPECTRUM_SOURCE_LANES` sets the lane capacity; surplus sources are
truncated and reported in the runtime UI. Lowerings use that fixed capacity
as `ColumnStride`, and `MIMIR_SPECTRUM_TUBE_SUBDIVISIONS` controls the
as `ColumnStride`. Physical history slots are addressed as a ring with
`RollingOffset`, so logical age no longer requires reshuffling every column
before shader sampling. `MIMIR_SPECTRUM_TUBE_SUBDIVISIONS` controls the
requested Catmull-Rom subdivision count so Fensalir's overflow report has a
direct cost lever.
- `MimirFensalirFieldLowering` now emits `AquariumFieldResourceDeclaration`

6
notes/current-system-map.md
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@ -391,8 +391,10 @@ its own age trail at `z = age * 0.1`. The resource advertises fixed history and
source-lane capacities, so content updates and source topology changes do not
resize the GPU buffer while the rolling trail fills. `MIMIR_SPECTRUM_SOURCE_LANES`
sets the fixed lane budget; surplus sources are truncated and reported in the
runtime UI. `MIMIR_SPECTRUM_TUBE_SUBDIVISIONS` is the runtime cost lever for
lowering Catmull-Rom subdivision count when Fensalir reports TubeField
runtime UI. Physical history slots are now addressed as a ring with
`RollingOffset`, so logical age no longer requires moving every column before
shader sampling. `MIMIR_SPECTRUM_TUBE_SUBDIVISIONS` is the runtime cost lever
for lowering Catmull-Rom subdivision count when Fensalir reports TubeField
truncation.
## Known Risks

2
src/Mimir.BufferSmoke/Program.cs
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@ -678,6 +678,7 @@ static int RunMimirSpectrumUploadSmoke()
const int expectedHistoryCount = 3;
const int expectedHistoryCapacity = 40;
const int expectedSubdivisions = 2;
const int expectedRollingOffset = (expectedHistoryCapacity - (expectedHistoryCount - 1)) * expectedSourceLaneCapacity;
var plannedTubePackets = plan.Packets
.Where(packet =>
packet.Backend == AquariumFieldBackendKind.TubeField &&
@ -714,6 +715,7 @@ static int RunMimirSpectrumUploadSmoke()
item.ColumnCount == expectedHistoryCount &&
item.ColumnStride == expectedSourceLaneCapacity &&
item.RollingModulo == resource.Height &&
item.RollingOffset == expectedRollingOffset &&
item.CatmullRomSubdivisions == expectedSubdivisions &&
Math.Abs(item.ColumnStep.Z - 0.1f) < 0.0001f &&
string.Equals(item.RampResourceKey, ramp.ResourceKey, StringComparison.Ordinal) &&

13
src/Mimir.Runtime/MimirRuntime.cs
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@ -278,9 +278,12 @@ public sealed class MimirRuntime : IAquariumRuntime
var sourceCount = sourceIds.Length;
var activeColumnCount = checked(sourceCount * historyCount);
var resourceColumnCapacity = checked(spectrumSourceLaneCapacity * SpectrumHistoryWindowCount);
var newestHistorySlot = PositiveModulo(-historyFrames[0].Sequence, SpectrumHistoryWindowCount);
var rollingOffset = checked(newestHistorySlot * spectrumSourceLaneCapacity);
var samples = new float[width * resourceColumnCapacity];
for (var historyIndex = 0; historyIndex < historyFrames.Length; historyIndex++)
{
var historySlot = PositiveModulo(-historyFrames[historyIndex].Sequence, SpectrumHistoryWindowCount);
foreach (var spectrum in historyFrames[historyIndex].Spectra)
{
if (!sourceIndexById.TryGetValue(spectrum.SourceId, out var sourceIndex))
@ -288,7 +291,7 @@ public sealed class MimirRuntime : IAquariumRuntime
continue;
}
var physicalColumn = historyIndex * spectrumSourceLaneCapacity + sourceIndex;
var physicalColumn = historySlot * spectrumSourceLaneCapacity + sourceIndex;
WriteNormalizedSpectrum(spectrum, samples.AsSpan(physicalColumn * width, width));
}
}
@ -378,7 +381,7 @@ public sealed class MimirRuntime : IAquariumRuntime
ColumnCount: historyCount,
ColumnStride: spectrumSourceLaneCapacity,
RollingModulo: resourceColumnCapacity,
RollingOffset: 0,
RollingOffset: rollingOffset,
Origin: new Vector3(-5.0f, sourceIndex * SpectrumChannelSeparation, 0.0f),
AxisStep: new Vector3(axisStepX, 0.0f, 0.0f),
ColumnStep: new Vector3(0.0f, 0.0f, SpectrumWindowDepthSeparation),
@ -451,6 +454,12 @@ public sealed class MimirRuntime : IAquariumRuntime
}
}
private static int PositiveModulo(long value, int modulo)
{
var remainder = value % modulo;
return (int)(remainder < 0 ? remainder + modulo : remainder);
}
private static Vector3 SpectrumCameraPosition(
int spectrumCount,
int windowCount,

1
state/evidence.jsonl
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@ -166,3 +166,4 @@
{"ts": "2026-05-27T11:38:16+01:00", "type": "implementation", "status": "ok", "note": "Mimir spectrum resource declarations now use fixed history capacity instead of growing with the currently filled trail. The runtime smoke proves 48 bands x 4 source lanes x 40 history capacity = 7680 uploaded floats while only the active history count is emitted through each source lowering. This avoids frame-to-frame GPU buffer resizing while preserving the rolling age trail."}
{"ts": "2026-05-27T11:41:00+01:00", "type": "implementation", "status": "ok", "note": "Mimir now exposes MIMIR_SPECTRUM_TUBE_SUBDIVISIONS as the first runtime cost lever for TubeField overflow. The spectrum upload smoke sets it to 2 and verifies every emitted source-lane TubeSpline lowering uses that Catmull-Rom subdivision count, so Fensalir's requested/dispatched/truncated segment report can be answered without changing code."}
{"ts": "2026-05-27T11:47:48+01:00", "type": "implementation", "status": "ok", "note": "Mimir spectrum upload now has fixed source-lane capacity as well as fixed history capacity. MIMIR_SPECTRUM_SOURCE_LANES sets the lane budget, TubeSpline lowerings use that budget as ColumnStride, surplus sources are truncated and reported in the runtime UI, and --mimir-spectrum-upload-smoke verifies 48 bands x 8 lanes x 40 history capacity = 15360 uploaded floats while emitting only four active TubeField claims/lowerings."}
{"ts": "2026-05-27T11:54:44+01:00", "type": "implementation", "status": "ok", "note": "Mimir spectrum history now uses true ring addressing. Physical history slots are keyed by sequence modulo the fixed history capacity, TubeSpline lowerings carry RollingOffset for newest logical age, and --mimir-spectrum-upload-smoke verifies the expected offset with the fixed 8-lane resource. This makes partial column uploads possible without changing shader sampling semantics."}

8
state/map.yaml
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@ -370,9 +370,11 @@ accepted_design:
the lane capacity; surplus sources are truncated and reported in the
runtime UI. Lowerings use that capacity as `ColumnStride` through the
shared Float32 resource so each active lane renders a true age trail at
`z = age * 0.1`. `MIMIR_SPECTRUM_TUBE_SUBDIVISIONS` controls the
Mimir-requested Catmull-Rom subdivisions so Fensalir's TubeField
truncation report has a direct cost lever.
`z = age * 0.1`. Physical history slots are addressed as a ring with
`RollingOffset`, so logical age no longer requires moving every column in
the upload matrix before shader sampling. `MIMIR_SPECTRUM_TUBE_SUBDIVISIONS`
controls the Mimir-requested Catmull-Rom subdivisions so Fensalir's
TubeField truncation report has a direct cost lever.
- `config/perfect-machine.example.json` declares live owners, sensors,
reservoir views, and runtime policy.
- `src/Mimir.Runtime/Synchronization` now includes the Perfect Machine module