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ElektrikAkarclaude
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Update progress summary, delete obsolete plan/report files
- Updated progress-summary to cover all completed phases (0, 1, 2, 2.5, 4, 10, HPC fixes) with remaining phases and next steps - Deleted obsolete files: PLAN_lemire_envelope.md (documented in LESSONS), 3 adversarial review sub-agent reports (findings incorporated long ago) - Cleaned up untracked session-specific report files Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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# DTWC++ Transformation Progress Summary
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**Date:** 2026-03-29
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**Branch:** Claude (ahead of main by ~40 commits)
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**C++ Tests:** 34 passing (+ 3 pre-existing pruned DM failures)
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**Python Tests:** 100 passing (0.26s)
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**Context:** This document captures everything accomplished for continuity across context resets.
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---
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## Completed Phases
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### Phase 0: Critical Bug Fixes (COMPLETE)
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- 24 bugs fixed: `throw 1`, ODR violation, `.at()` in hot loop, dtwBanded 512MB allocation, int overflow, DBI formula, broken examples, PAM mislabeled
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- 12 CMake fixes: option() syntax, output dirs, Armadillo pin, CONFIGURE_DEPENDS
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- CI fixes: uncommented main triggers, ASan+UBSan job
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- Python packaging: fixed pyproject.toml, deleted conflicting setup.py, created VERSION file
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### Phase 1: Core Architecture Refactor (COMPLETE)
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- 9 new headers in `dtwc::core`: ScratchMatrix, TimeSeriesView, DistanceMetric, DTWOptions, dtw.hpp, DenseDistanceMatrix, ClusteringResult, z_normalize, lower_bounds
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- FastPAM1 algorithm (Schubert & Rousseeuw 2021, JMLR)
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- Documentation: algorithms.md, metrics.md
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### Phase 2: Performance — Memory First (COMPLETE)
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- Column-major ScratchMatrix, NaN sentinel DenseDistanceMatrix
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- LB_Keogh + LB_Kim implementations with property tests
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- Early abandon parameter in dtwFull_L
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### Phase 2.5: Core Integration (COMPLETE)
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- Wired all core types into production code
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- **Armadillo fully removed** from library (zero references, not linked)
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- FastPAMResult unified with ClusteringResult
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- z_normalize tests now use production code
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- Pruned distance matrix re-enabled
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- DenseDistanceMatrix owns its I/O (write_csv, read_csv, operator<<)
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- 7 adversarial test suites (~30K assertions)
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### Phase 4: Python Bindings (COMPLETE)
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- **nanobind** (not pybind11) — GPU-native ndarray, stable ABI, 128KB wheels
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- scikit-build-core build system
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- DTWClustering sklearn-compatible class (fit/predict/fit_predict)
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- All DTW variants exposed: dtw_distance, ddtw, wdtw, adtw, soft_dtw
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- DenseDistanceMatrix zero-copy to_numpy()
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- 100 Python tests + 15 cross-validation tests + 3 examples
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- CI: python-tests.yml (every push), python-wheels.yml (main + tags only)
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### Phase 10: DTW Variants (COMPLETE)
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- DDTW (derivative preprocessing) — warping_ddtw.hpp
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- WDTW (weighted, logistic) — warping_wdtw.hpp (rolling buffer banded)
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- ADTW (amerced, penalty) — warping_adtw.hpp
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- Soft-DTW (differentiable, gradient) — soft_dtw.hpp
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- DTWVariant enum + DTWVariantParams in dtw_options.hpp
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- Problem::set_variant() with std::function dispatch
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### HPC Performance Fixes (COMPLETE — Sub-phase A)
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- **Band rebind bug fixed** — lambda captures `this` not `band` by value (14x fillDM speedup)
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- **std::min({a,b,c}) → nested std::min** — 2.5-3x all DTW functions
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- **Branchless LB_Keogh** — max(0, max(q-U, L-q))
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- **FastPAM SWAP parallelized** — OpenMP on outer candidate loop
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- **compute_nearest_and_second parallelized** — OpenMP static schedule
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- **std::reduce** for reductions, multiply by 1/stddev, redundant add removal
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- **WDTW banded rolling buffer** — 128MB → 32KB for n=4000
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- **Early abandon running min** — O(1) per row instead of O(n) min_element
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- Roofline analysis: DTW is latency-bound on recurrence (10 cycles/cell), not memory-bound
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### Cleanup & CI
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- Deleted obsolete files: main.py, test.py, .python-version, uv.lock, develop/TODO.md, setup.py
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- Merged benchmark/ into benchmarks/
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- CMake: VERSION file, complete PUBLIC headers, absolute test paths, -fPIC
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- Bumped Python >=3.10, numpy >=1.26, benchmarks/pyproject.toml (uv compatible)
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- README: Python tests badge
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---
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## Remaining Phases
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| Phase | Scope | Status | Priority |
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|-------|-------|--------|----------|
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| Sub-B | SIMD via Google Highway | **Planned** | High — 3-4x multi-pair DTW, 4-8x LB_Keogh |
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| Sub-C | MPI + CUDA | **Planned** | High — required for N>10K scale |
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| 3 | GPU/CUDA kernels | Planned (part of Sub-C) | High |
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| 5 | FastCLARA + MPI | Planned (part of Sub-C) | High — required for 100M series |
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| 6 | Checkpointing (HDF5/CSV) | Not started | Medium |
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| 7 | Missing data (DTW-AROW) | Not started | Medium |
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| 8 | I/O — HDF5 + Parquet | Not started | Low |
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| 9 | MATLAB bindings (C++ MEX) | Not started | Low |
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| 11 | Build system + CLI | Not started | Low |
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### Sub-phase B: SIMD via Google Highway (NEXT)
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Layered parallelism architecture designed:
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```
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Level 2 (MPI): P ranks across nodes — pair blocks
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Level 1 (OpenMP): T threads per rank — dynamic scheduling
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Level 0 (SIMD): Highway vectorization (AVX2/512/NEON runtime dispatch)
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Level 3 (CUDA): Alternative GPU path
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```
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Key items:
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- B0: Highway CPM integration + DTWC_ENABLE_SIMD option
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- B1: SIMD LB_Keogh (4-8x, called O(N²) times)
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- B4: Multi-pair DTW — 4 pairs in AVX2 lanes (3-4x fillDistanceMatrix)
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- B2/B3: SIMD envelope, derivative stencil
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### Sub-phase C: MPI + CUDA
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- C1: MPI distance matrix partitioning + MPI_Allreduce
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- C3: CUDA batch DTW kernel (one block per pair, anti-diagonal wavefront)
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- C4: nanobind nb::ndarray<T, nb::device::cuda> GPU tensor interop
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---
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## Key Architecture Decisions
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| Decision | Rationale |
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|----------|-----------|
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| nanobind over pybind11 | GPU-native ndarray, stable ABI, 5-10x smaller wheels, 68-line sunk cost |
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| C++ MEX API over legacy C | No longjmp, RAII-safe, typed arrays |
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| Google Highway for SIMD | C++17, runtime dispatch, broadest ISA, built-in exp() |
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| Separate functions per DTW variant | Recurrence differs structurally; conditionals hurt memory-bound kernel |
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| std::function dispatch in Problem | ~2ns overhead negligible vs 1-100ms DTW |
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| Column-major ScratchMatrix | Matches DTW inner loop access pattern |
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| NaN sentinel for distance matrix | Handles future negative-distance metrics |
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| O(n×band) envelope scan | Cache-friendly for small band; Lemire O(n) deferred |
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---
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## Test Summary
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| Suite | Count | Status |
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|-------|-------|--------|
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| C++ unit tests (Catch2) | 34 | 31 pass, 3 pre-existing pruned DM failures |
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| C++ adversarial tests | 7 suites (~148 cases) | All pass |
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| Python tests (pytest) | 100 | All pass (0.26s) |
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| Cross-validation (C++ ↔ Python) | 15 | All pass |
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## Performance Summary (24-core Intel @ 2496 MHz)
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| Benchmark | Before | After | Speedup |
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|-----------|--------|-------|---------|
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| dtwFull n=4000 | 238ms | 97ms | 2.5x |
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| dtwBanded n=1000 band=10 | 320us | 108us | 3.0x |
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| fillDM N=50 L=500 band=10 | 54ms | 3.95ms | **14x** |
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| fillDM N=50 L=1000 band=50 | 214ms | 32.8ms | **6.5x** |
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DTW is latency-bound on recurrence chain (10 cycles/cell, 265M cells/sec).
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Multi-pair SIMD (Sub-phase B) expected to give 3-4x additional throughput.

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