diff --git a/backlog/features/2025-08-15_lfm-kernel-code-review.md b/backlog/features/2025-08-15_lfm-kernel-code-review.md index 8c53d7ff..c93a9cd0 100644 --- a/backlog/features/2025-08-15_lfm-kernel-code-review.md +++ b/backlog/features/2025-08-15_lfm-kernel-code-review.md @@ -1,7 +1,7 @@ --- id: "lfm-kernel-code-review" title: "Review existing LFM kernel implementations" -status: "Ready" +status: "In Progress" priority: "High" created: "2025-08-15" last_updated: "2025-08-15" @@ -26,8 +26,8 @@ Conduct a comprehensive review of existing LFM (Latent Force Model) kernel imple - Need to understand differences and identify modernization opportunities ## Tasks -- [ ] Review `GPy/kern/src/eq_ode1.py` and `eq_ode2.py` implementations -- [ ] Analyze MATLAB LFM implementation structure and patterns +- [x] Review `GPy/kern/src/eq_ode1.py` and `eq_ode2.py` implementations +- [x] Analyze MATLAB LFM implementation structure and patterns - [ ] Document current limitations and inconsistencies - [ ] Identify reusable components and design patterns - [ ] Compare parameter handling approaches @@ -50,3 +50,26 @@ Conduct a comprehensive review of existing LFM (Latent Force Model) kernel imple ## Related - CIP: 0001 (LFM kernel implementation) - Papers: Álvarez et al. (2009, 2012), Lawrence et al. (2006) + +## Progress Updates + +### 2025-08-15 +Started code review task. Initial findings: + +**GPy Implementations:** +- `EQ_ODE1`: First-order differential equation kernel with decay rates and sensitivities +- `EQ_ODE2`: Second-order differential equation kernel with spring/damper constants +- Both use GPy's multioutput approach with output index as second input dimension +- Complex kernel computation with multiple covariance types (Kuu, Kfu, Kuf, Kusu) +- Uses `@Cache_this` decorator for performance optimization + +**MATLAB Implementation:** +- More complete framework with `lfmCreate`, `lfmKernCompute`, `lfmKernParamInit` +- Uses multi-kernel approach with parameter tying +- Supports multiple displacements driven by multiple forces +- Cleaner separation of concerns with dedicated model creation + +**Key Differences:** +- GPy uses single kernel class per ODE order, MATLAB uses multi-kernel composition +- GPy has more complex index handling for multioutput +- MATLAB has better parameter organization and tying mechanisms