Fix convergence issues in split ODE methods #2861
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ChrisRackauckas-Claude
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After DiffEqBase.jl PR SciML#1188 stopped replacing LazyBufferCache in promote_f, split ODE methods started failing convergence tests due to uninitialized memory in caches. This fix uses fill! to zero out the cache when a SplitFunction with a cache is initialized, ensuring clean initial state. Changes: - Add PreallocationTools as a dependency to OrdinaryDiffEqCore - Use fill! to zero out SplitFunction caches during initialization - Requires PreallocationTools v0.4.34+ which adds fill! overloads for cache types The fix uses the standard fill! function which works with PreallocationTools.jl PR SciML#142 that adds fill! overloads for cache types. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <[email protected]>
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Summary
Fixes convergence test failures in split ODE methods (AlgConvergence_III and others) by ensuring caches are properly initialized.
Background
After DiffEqBase.jl PR #1188 changed
promote_fto no longer replaceLazyBufferCachewith a zero-initialized array, split ODE methods started failing convergence tests. The issue was that uninitialized memory in the cache contained random values that would accumulate into the solution, causing unpredictable errors that broke convergence rate tests.Solution
This PR uses the standard
fill!function to zero out the cache forSplitFunctionobjects during integrator initialization. It adds PreallocationTools as a dependency and requires version 0.4.34+ which includesfill!overloads for cache types.Changes
fill!(cache, 0)to zero out SplitFunction caches during initializationfill!is applicable before calling it, ensuring backward compatibilityTest Results
Created a test that verifies convergence rates for
SplitEulerwith aLazyBufferCache. The test shows correct first-order convergence (rates ≈ 1.0) with this fix applied.Dependencies
fill!overloads for cache typesRelated Issues
🤖 Generated with Claude Code