Current Hotspot Audit

What This Is

This is a static audit of the current repo for likely allocation, scan, and driver-pressure hotspots. It is not a profiler output. Treat it as a list of places to benchmark once the next implementation cut starts.

High-Risk Runtime Hotspots

MimirAudioSynchronizationAnalyzer.Analyze

Why it is hot:

• Called repeatedly by MimirSynchronizationHub.
• Extracts windows from rolling buffers.
• Converts PCM formats.
• Resamples candidate windows.
• Invokes passive or active decode.

Risk shape:

• ExtractMonoWindow builds a List<float> and returns ToArray.
• Candidate windows can be re-extracted on every analysis step.
• Resampling allocates a new output array.
• Reports/traces allocate lists and records.

Coherent next cut:

• Add an analyzer scratch/context object owning reusable buffers.
• Add streaming active decoder state so repeated windows are not rescanned.
• Cache reference extracted window/spectrum per analysis edge.

MimirChirpBinTimeline.DecodeStreamWindow

Why it is hot:

• Current active path for chirp-only/hybrid sync.
• Runs event proposal, classification, anchor decode, clock fit.

Risk shape:

• BuildWindowEnergyTrace allocates prefix/output arrays.
• DetectFrames sorts proposals by energy.
• ScoreBins scores every symbol for each candidate.
• DecodeAnchors creates candidate windows and path arrays.
• LINQ/ToArray appears in several inner-ish paths.

Coherent next cut:

• Split into streaming proposal state and stateless symbol scorer.
• Replace LINQ in candidate/code paths with bounded arrays/spans once behavior is frozen.
• Move calibration likelihood into the scoring stage before candidate pruning.

MimirPassiveAudioSynchronizationEstimator.Estimate

Why it is hot:

• Passive/hybrid mode can compare multiple sources.
• FFT arrays allocate per estimate.

Risk shape:

• Complex[] reference/candidate arrays per call.
• Hann/preemphasis recomputed per call.
• Reference FFT repeated for each candidate.

Coherent next cut:

• Scratch object with reusable complex buffers.
• Precomputed window.
• Reference spectrum cache per edge.
• Limit lag search by known physical/network horizon.

MimirRuntime.QueueCalibrationTimeline

Why it is hot-ish:

• Renders/encodes active witness audio inside runtime update.

Risk shape:

• Allocates PCM bytes and base64 every batch.
• Renders sine chirps with scalar Math.Sin.

Coherent next cut:

• For production, move witness generation to a reusable native/DSP oscillator or pre-rendered segment ring. Keep runtime policy, move audio hot work.

Native Hotspots

native/asio_capture/pushInputBlocks

Why it is hot:

• Runs from ASIO callback.
• Copies every input channel into a queued std::vector<float>.

Risk shape:

• Allocates/copies per channel block.
• Uses mutex-protected deque.

Current acceptability:

• Fine for proof and likely fine for four Scarlett channels at 192 kHz in short term.

Coherent next cut:

• Preallocated block pool or SPSC ring if profiling shows callback pressure.

native/probes/ks_camera_cadence/measureCandidate

Why it is hot:

• Direct KS async read queue for camera cadence.

Risk shape:

• Diagnostic stdout and optional JSON events.
• Probe code owns too much CLI behavior for production.

Coherent next cut:

• Extract the async read queue shape into a direct driver worker, minus stdout and measurement ceremony.

native/reservoir/RollingReservoir

Why it matters:

• Intended lower shared-edge retention authority.

Risk shape:

• Current Rust VecDeque and typed-view iteration are conceptually clean but not necessarily the final cache-optimal layout.

Coherent next cut:

• Keep invariant. Replace storage only when Fensalir/Faust integration proves the need.

Allocation Smells Found By Static Scan

Likely production-relevant:

• MimirChirpBinTimeline: repeated List<>, ToArray, sorting, grouping in decode path.
• MimirAudioSynchronizationAnalyzer: window extraction and resampling arrays.
• MimirPassiveAudioSynchronizationEstimator: per-call FFT arrays.
• MimirAsioStreamSource: per-block byte arrays after native read.
• MimirRollingStreamBuffer.Snapshot: full array snapshot for readers.

Mostly diagnostic:

• Mimir.BufferSmoke allocations.
• Native probe stdout/JSON allocations.
• Bridge scripts.

Rule For Next Optimization

Do not optimize the whole repo. Pick one measured hot path:

1. physical chirp-bin decode;
2. passive FFT reuse;
3. ASIO queue pressure;
4. camera driver handoff.

Then make one ownership-improving cut and benchmark before widening.